By William Harwood
CBS News/Kennedy Space Center

The following copy originally was posted on the Current Mission space page at http://cbsnews.com/network/news/space/current.html.

Comments, suggestions and corrections welcome!

TABLE OF CONTENTS

• 02/20/08: Space shuttle Atlantis returns to Earth
• 02/20/08: Shuttle crew set for landing
• 02/19/08: Deorbit timelines
• 02/19/08: Good weather expected in Florida for Wednesday landing
• 02/19/08: Astronauts pack for re-entry, test critical systems; shuttle reoriented to warm thruster with failed heater
• 02/18/08: Engineers troubleshoot vernier thruster heater glitch
• 02/18/08: Shuttle crew begins final heat shield inspection
• 02/18/08: Atlantis undocks from space station
• 02/18/08: Shuttle crew gears up for undocking
• 02/17/08: Shuttle astronauts bid station crew farewell
• 02/17/08: Astronauts wrap up joint operations; farewell ceremony on tap
• 02/16/08: Station, shuttle commanders say satellite shoot-down no threat
• 02/16/08: Station reboost, crew news conference on tap
• 02/15/08: NASA will activate Florida, California landing sites to ensure shuttle return before satellite shoot down
• 02/15/08: Spacewalk ends; all major objectives accomplished
• 02/15/08: Spacewalk begins
• 02/15/08: Astronauts suit up for final spacewalk
• 02/14/08: 'Love Crater,' starboard SARJ inspections added to Friday spacewalk
• 02/13/08: Spacewalk ends; mission extended one day
• 02/13/08: Spacewalk begins
• 02/13/08: Walheim, Schlegel suit up for spacewalk
• 02/12/08: Schlegel 'anxious' about spacewalk Wednesday; won't discuss illness but says he's good to go
• 02/12/08: European astronauts begin Columbus activation
• 02/11/08: Astronauts gear up for Columbus ingress, outfitting
• 02/11/08: Spacewalk ends
• 02/11/08: Columbus module attached to space station
• 02/11/08: Astronauts told to wrap up spacewalk
• 02/11/08: Station arm pulls Columbus module from cargo bay
• 02/11/08: Spacewalkers work to install robot arm fixture on Columbus module
• 02/11/08: Spacewalk begins
• 02/11/08: Walheim, Love suit up for Columbus install spacewalk
• 02/10/08: Schlegel expected to participate in Wednesday spacewalk
• 02/10/08: Revised flight day 4 timeline
• 02/10/08: Flight plan revised; equipment transfers, blanket inspection on tap
• 02/09/08: Spacewalk delayed 24 hours by crew medical issue; Schlegel to be replaced by Love on first spacewalk; Shannon confirms mission extension, refuses to discuss reasons for delay
• 02/09/08: Engineers assessing pulled-up insulation blanket; computer issue
• 02/09/08: Shuttle Atlantis docks with space station
• 02/09/08: Shuttle crew begins terminal phase of space station rendezvous
• 02/09/08: Astronauts gear up for rendezvous and docking
• 02/08/08: No obvious debris damage; shuttle performance near flawless going into Saturday docking
• 02/08/08: Astronauts inspect heat shield
• 02/07/08: Shuttle Atlantis rockets into space (UPDATED at 5:25 p.m. with quotes from post-launch news conference; initial debris report)
• 02/07/08: Griffin pleased with ECO recovery work; downplays concern about Ares 1 rocket
• 02/07/08: Astronauts strap in for launch
• 02/07/08: Fueling complete; ECO sensors operating normally
• 02/07/08: ECO sensors pass initial health checks
• 02/07/08: Shuttle fueling begins; weather remains a concern
• 02/06/08: Weather forecast now 70 percent 'no go' for Thursday launch
• 02/05/08: Cain confident ECO sensors will work properly
• 02/05/08: Countdown on track
• 02/04/08: Countdown begins
• 02/04/08: STS-122 mission preview
• 02/04/08: Astronauts arrive for Thursday launch; weather an issue
• 02/01/08: NASA managers opt to press ahead for 02/7 launch pending successful flex hose retraction, final engineering analysis
• 01/30/08: Satisfied ECO sensor issue resolved, engineers troubleshoot kink in Freon hose; decision expected Saturday on Feb. 7 launch
• 01/11/08: Russian Progress launch moved up; Atlantis retargeted for Feb. 7; station spacewalk on tap
• 01/08/08: Connector upgrade ready for installation; lab testing continues
• 01/03/08: Shuttle launch no earlier than Jan. 24 as NASA pursues parallel ECO testing/hardware replacement
• 12/27/07: NASA orders external ECO sensor plug/socket replacement with soldered components; launch date under review
• 12/21/07: Hale hopeful near-term fix possible for ECO sensors; engineers tentatively cleared to remove suspect connector, plug
• 12/18/07:Sensor problem tracked to external tank wiring connector; corrective actions, impact on launch date not yet known
• 12/18/07: Initial sensor troubleshooting work complete; engineers ready to drain tank
• 12/18/07: ECO sensor 1 fails; sensors 2 and 3 show intermittent problems
• 12/18/07: Shuttle fueling test begins
• 12/13/07: Launch no earlier than Jan. 10; station spacewalk, tanking test on tap Dec. 18
• 12/11/07: Tanking test planned to help pinpoint ECO sensor problem
• 12/09/07: Launch delayed to January; station crew told to plan for possible spacewalk to inspect stalled rotary joint
• 12/09/07: ECO sensor No. 3 fails initial health chec
• 12/08/07: NASA clears Atlantis for Sunday launch try
• 12/08/07: Engineers troubleshoot circuit breaker trips on space station solar arrays
• 12/07/07: NASA tentatively resets shuttle launch for Sunday pending final analysis
• 12/07/07: Engineers assess launch options
• 12/06/07: Launch delayed at least 48 hours; engineers trying to develop rationale to fly as is
• 12/06/07: Launch director hopeful about ECO sensor fix
• 12/06/07: Shuttle launch scrubbed
• 12/06/07: ECO sensor background
• 12/06/07: Engine cutoff sensor issue
• 12/06/07: Shuttle Atlantis fueled for launch
• 12/05/07: Weather still 90 percent 'go;' countdown proceeding smoothly
• 12/03/07: Atlantis crew flies to KSC; countdown begins
• 11/30/07: Atlantis cleared for Dec. 6 launch
• 11/10/07: Atlantis hauled to launch pad

09:30 AM, 2/20/08, Update: Space shuttle Atlantis returns to Earth (UPDATED at 12:30 p.m. with quotes from Frick; news conference; bad weather in Pacific may delay satellite shoot down)

Taking advantage of calm weather, the shuttle Atlantis dropped out of orbit and glided to a smooth Florida landing today, closing out an extended 13-day mission to deliver a new European research lab and a French astronaut to the international space station.

Bringing outgoing space station flight engineer Dan Tani back to Earth after 120 days in space, Atlantis commander Steve Frick guided Atlantis through a sweeping 235-degree left overhead turn, lined up on runway 15 at the Kennedy Space Center and swooped to a picture-perfect touchdown at 9:07:10 a.m.

"Houston, Atlantis, wheels stopped," Frick radioed as the shuttle rolled to a halt.

"Copy, wheels stopped," astronaut Jim Dutton replied from mission control in Houston. "Welcome home, Atlantis, welcome home, Dan, and congrats on delivering (the) Columbus (module) to its new world."

"It's been a great mission," Frick said. "We're extremely happy to be home, it's such a beautiful day in Florida. We can't wait to see our families, who hopefully were all at the (grand)stands here watching. We appreciate all the great help and support from the folks here at Kennedy and all over NASA, and especially at Johnson Space Center, mission control, for keeping us safe when we were airborne and bringing us safely home,"

"We really appreciate those words, Steve," replied astronaut Jim Dutton in mission control.

Mission duration was 12 days 18 hours 21 minutes and 40 seconds, covering 202 complete orbits and 5.3 million miles since blastoff Feb. 7. Bill Gerstenmaier, director of space flight operations at NASA headquarters in Washington. said Tani came through re-entry and the return to Earth's gravity in good shape.

"He's doing great," Gerstenmaier said. "He'll go back to Houston and start some rehabilitation, start doing some weight training, some water training, those kind of things, and eventually get back into a pretty routine lifestyle."

With Atlantis and its seven-member crew safely home, the Pentagon was clear to proceed with plans to destroy a falling spy satellite with a dramatic missile shot from a Navy cruiser west of Hawaii.

The unprecedented intercept had been planned for this evening, but Pentagon officials said this morning high seas near Hawaii threatened to delay the launching. A second opportunity was available Thursday.

Launched in December 2006, the classified National Reconnaissance Office satellite, believed to be an experimental spacecraft intended to test new sensor technologies, suffered a catastrophic malfunction shortly after reaching orbit. It has been out of contact and out of control ever since, slowly falling back to Earth due to the long-term affects of atmospheric friction.

Left on its own, the 5,000-pound NROL-21 spacecraft would re-enter the atmosphere and break apart in mid March. About 2,400 pounds of debris could be expected to survive re-entry and make it all the way to the surface. The risk of injury from satellite debris is considered minimal, but the Bush administration, worried the satellite's full load of toxic, now-frozen hydrazine rocket fuel might make it to the ground, ordered the Navy to attempt a shoot down.

The avoid any risk of debris that might threaten Atlantis and its crew, the shot was held up until Atlantis could return to Earth. Playing it safe, NASA staffed a backup landing site at Edwards Air Force Base, Calif., to get the shuttle down today, on one coast or the other. As it turned out, the weather cooperated in Florida and Edwards wasn't needed.

Flying upside down and backward 212 miles above the Indian Ocean, Frick and pilot Alan Poindexter fired Atlantis' twin braking rockets at 7:59:52 a.m. for two minutes and 43 seconds, slowing the ship by about 198 mph to drop out of orbit (ground-track mapss).

A half hour later, descending through 76 miles above the south Pacific Ocean, Atlantis plunged back into the discernible atmosphere around 8:36 a.m., entering the zone of peak heating a few minutes later.

Following a southwest-to-northeast trajectory that carried the ship high above central America just south of the Yucatan Peninsula, Atlantis skirted the western tip of Cuba before crossing the southwest coast of Florida near Fort Myers.

Frick took over manual control as the shuttle descended through 51,000 feet and dropped below the speed of sound around 9:03 a.m. Approaching the Kennedy Space Center the southwest, he and Poindexter guided the ship through a sweeping left overhead turn to line up on runway 15.

Frick, Poindexter, flight engineer Rex Walheim, Leland Melvin, Stan Love and European Space Agency astronaut Hans Schlegel were expected to doff their pressure suits and climb out of the shuttle an hour or so after touchdown. Tani made the return to Earth strapped into a reclining seat on the shuttle's lower deck and flight surgeons were standing by to provide assistance as needed.

After medical exams and reunions with friends and family members, all seven astronauts were expected to fly back to the Johnson Space Center in Houston on Thursday.

Tani was launched to the space station aboard the shuttle Discovery last October to help commander Peggy Whitson and flight engineer Yuri Malenchenko prepare the outpost for the attachment of the European Space Agency's Columbus research module. The new lab module was scheduled to be carried aloft aboard Atlantis in December along with Tani's replacement, French astronaut Leopold Eyharts.

But Atlantis was grounded by problems with hydrogen fuel sensors, Columbus' delivery was held up and Tani's stay in space ultimately was extended for two months. As such, he missed the holidays with his family and was off the planet when his 90-year-old mother was killed in a Dec. 19 car wreck.

After extensive modifications to a suspect fuel sensor wiring connector, Atlantis blasted off at 2:45:30 p.m. on Feb. 7 to kick off the delayed assembly mission.

Over the next 13 days, the astronauts staged three spacewalks, delivered and installed the 26,627-pound Columbus module, two external experiment packages totaling 1,409 pounds and a fresh tank of high-pressure nitrogen for the station's ammonia cooling system that tipped the scales at 1,.069 pounds.

The shuttle brought 2,242 pounds of station hardware back to Earth in its cargo bay, including a spent nitrogen tank and a faulty control moment gyroscope. Some 1,299 pounds of supplies and equipment were transferred from the shuttle cabin to the space station, including a new solar alpha rotary joint drive motor, and 1,343 pounds of equipment was moved from the station to the shuttle's cabin for return to Earth.

The astronauts transferred 1,386 pounds of fresh water to the space station, 95 pounds of oxygen and 27 pounds of nitrogen.

"It's great... to be back on the ground here at the Kennedy Space Center on our first try," Frick said from the runway. "As you can see, the weather is gorgeous and it looked just as nice from up high as it does down here. Atlantis is a great ship, itÊbrought us home without any troubles, everything worked just beautifully. We're obviously very excited that our mission is complete and successful, we got everything done that we had hoped to get done."

With Atlantis safely home, NASA engineers will set their sights on launching the shuttle Endeavour March 11 on a marathon 16-day five-spacewalk mission to attach the first of two Japanese research modules to the space station. Endeavour's crew is scheduled to fly to the Florida space center Saturday to participate in a dress-rehearsal countdown Monday.

If all goes well, Endeavour will rocket away around 2:28 a.m. on March 11 and return to Earth around 7:40 p.m. on March 26.

The next flight in the sequence, a mission by Discovery to carry Japan's huge Kibo module to the station, has slipped from the end of April to around May 25 because of unfavorable orbital conditions and time needed to complete external tank processing.

After that, Atlantis is scheduled to return to space Aug. 28 on a long-awaited flight to service the Hubble Space Telescope. Two more flights, by Endeavour and Discovery in October and December, will ferry supplies to the space station and a final set of solar arrays.

4:45 AM, 2/20/08, Update: Shuttle crew set for landing

Commander Steve Frick and his six crewmates are rigging the shuttle Atlantis for re-entry and landing at the Kennedy Space Center today around 9:07 a.m. to close out an extended 13-day space station assembly mission. There are no technical problems of any significance and forecasters continue to predict good weather at the Florida spaceport.

"We're really looking forward to entry day today and landing on the first rev at Kennedy Space Center," pilot Alan Poindexter radioed when the crew was awakened around 12:45 a.m. "We want to thank everyone for all the hard work they've done to get us ready for today. We're ready to get to work."

Chief astronaut Steve Lindsey, flying a NASA training jet over the Kennedy Space Center around 4:45 a.m., reported "starry skies and light winds, no weather issues at all, at least at this hour," said mission control commentator Rob Navias. "Everything continuing to shape up weather wise."

Assuming no dramatic changes, Frick and Poindexter plan to fire Atlantis' twin braking rockets at 7:59:54 a.m. for two minutes and 39 seconds, slowing the ship by about 198 mph to drop out of orbit (ground-track mapss).

After a half-hour fall to an altitude of about 76 miles above the south Pacific Ocean, Atlantis will plunge back into the discernible atmosphere around 8:36 a.m., entering the zone of peak heating a few minutes later. Following a southwest-to-northeast trajectory that will carry the ship high above central America just south of the Yucatan Peninsula, Atlantis will skirt the western tip of Cuba before crossing the southwest coast of Florida near Fort Myers.

Frick plans to take over manual control of the shuttle as it drops below the speed of sound at an altitude 50,700 feet around 9:03 a.m. Approaching from the southwest, he will guide the ship through a sweeping 301-degree right-hand overhead turn to line up on runway 33 for a landing around 9:07:39 a.m.

Frick, Poindexter, flight engineer Rex Walheim, Leland Melvin, Stan Love and European Space Agency astronaut Hans Schlegel will be joined for the trip home by space station astronaut Dan Tani, returning to Earth after 120 days in space. To ease his return to the unfamiliar tug of Earth's gravity, Tani planned to make the trip home strapped into a reclining seat on the shuttle's lower deck.

Frick and his crewmates have four landing opportunities today on successive 90-minute orbits, two at Kennedy followed by two at Edwards Air Force Base in California's Mojave Desert. The shuttle has enough supplies to remain in orbit until Friday in a worst-case scenario, but NASA managers activated Edwards today to get Atlantis down, on one coast or the other, to clear the way for a Navy attempt to destroy a falling spy satellite.

Based on the satellite's orbital track and a variety of government advisories establishing a restricted zone west of Hawaii, amateur satellite trackers believe the first opportunity for a Navy cruiser to fire a missile at the crippled satellite is around 10:30 p.m. EST this evening.

Given the forecast in Florida, it would appear the Atlantis astronauts have a good shot at making it home on the first landing opportunity today to close out a 5.3-million-mile mission spanning 202 complete orbits since blastoff Feb. 7.

Here are timelines for the first two Florida landing opportunities (in EST; deorbit burn time subject to minor changes):

EST...........EVENT

FIRST FLORIDA OPPORTUNITY: Rev. 202 Deorbit to Kennedy Space Center, Fla.

04:00 AM......Deorbit timeline begins
04:15 AM......Radiator stow complete
04:25 AM......Mission specialists seat installation
04:31 AM......Computers set for deorbit prep
04:35 AM......Hydraulic system prepared for entry
05:00 AM......Flash evaporator cooling system checkout
05:06 AM......Final payload deactivation
05:20 AM......Payload bay doors closed
05:30 AM......Mission control 'go' for OPS-3 entry software load
05:40 AM......OPS-3 transition
06:05 AM......Entry switchlist verification
06:15 AM......Deorbit maneuver update
06:20 AM......Crew entry review
06:35 AM......Commander/pilot don entry suits
06:52 AM......Inertial measurement unit alignment
07:00 AM......CDR/PLT strap in; mission specialists don suits
07:17 AM......Shuttle steering check
07:20 AM......Hydraulic power system prestart
07:27 AM......Toilet deactivation
07:35 AM......Payload bay vent doors closed for entry
07:40 AM......Mission control 'go' for deorbit burn
07:46 AM......Mission specialists seat ingress
07:55 AM......Single hydraulic power unit start

07:59:54 AM...Deorbit ignition (dV: 197.7 mph; dT: 02:39)
08:02:33 AM...Deorbit burn complete (altitude: 211.6 sm)

08:35:59 AM...Atmospheric entry (altitude: 75.6 sm)
08:40:59 AM...1st roll command to left
08:52:05 AM...1st left-to-right roll reversal
08:54:00 AM...C-band radar acquisition
09:01:06 AM...Velocity less than mach 2.5 (altitude: 84,200 feet)
09:03:18 AM...Velocity less than mach 1 (altitude: 50,700 feet)
09:03:42 AM...Shuttle banks 301 degrees to line up on runway 33
09:07:39 AM...Landing

SECOND FLORIDA OPPORTUNITY: Rev. 203 Deorbit to Kennedy

09:15 AM......Mission control 'go' for deorbit burn
09:21 AM......MS seat ingress
09:30 AM......Single APU start

09:35:20 AM...Deorbit ignition (dV: 195.7 mph; dT: 02:38)
09:37:58 AM...Deorbit burn complete (altitude: 214.5 sm)

10:11:00 AM...Entry interface (altitude: 75.6 sm)
10:15:57 AM...1st roll command to right
10:27:46 AM...1st right-to-left roll reversal
10:36:05 AM...Velocity less than mach 2.5 (altitude: 84,700 feet)
10:38:18 AM...Velocity less than mach 1 (altitude: 50,200 feet)
10:38:55 AM...Shuttle banks 269 degrees to line up on runway 33
10:42:35 AM...Landing

2:20 PM, 2/19/08, Update: Deorbit timelines

Here are detailed deorbit timelines for all four of the shuttle Atlantis' landing opportunities Wednesday (in EST throughout; times may change slightly; best viewed with fixed-width font):

EST...........EVENT

FIRST FLORIDA OPPORTUNITY: Rev. 202 Deorbit to Kennedy Space Center, Fla.

12:45:00 AM...Crew wakeup
03:59:54 AM...Begin deorbit timeline
04:14:54 AM...Radiators stowed
04:24:54 AM...Mission specialists seat installation
04:30:54 AM...Computers set for deorbit prep
04:34:54 AM...Hydraulic system prepared for entry
04:59:54 AM...Flash evaporator cooling system checkout
05:05:54 AM...Final payload deactivation
05:19:54 AM...Payload bay doors closed
05:29:54 AM...Mission control 'go' for OPS-3 entry software load
05:39:54 AM...OPS-3 transition
06:04:54 AM...Entry switch list verification
06:14:54 AM...Deorbit burn update
06:19:54 AM...Crew entry review
06:34:54 AM...Commander/pilot don entry suits
06:51:54 AM...Inertial measurement unit alignment
06:59:54 AM...Commander/pilot strap in; others don suits
07:16:54 AM...Shuttle steering check
07:19:54 AM...Hydraulic power system prestart
07:26:54 AM...Toilet deactivation
07:34:54 AM...Payload bay vent doors closed for entry
07:39:54 AM...MIssion control 'go' for deorbit burn
07:45:54 AM...Mission specialists seat ingress
07:54:54 AM...Single hydraulic power unit start

07:59:54 AM...Deorbit ignition (dV: 197.7 mph; dT: 02:39)
08:02:33 AM...Deorbit burn complete (altitude: 211.6 sm)

08:35:59 AM...Atmospheric entry (altitude: 75.6 sm)
08:40:59 AM...1st roll command to left
08:52:05 AM...1st left-to-right roll reversal
08:54:00 AM...C-band radar acquisition
09:01:06 AM...Velocity less than mach 2.5 (altitude: 84,200 feet)
09:03:18 AM...Velocity less than mach 1 (altitude: 50,700 feet)
09:03:42 AM...Shuttle banks 301 degrees to line up on runway 33
09:07:39 AM...Landing

SECOND FLORIDA OPPORTUNITY: Rev. 203 Deorbit to Kennedy

09:15:20 AM...Mission control 'go' for deorbit burn
09:21:20 AM...MS seat ingress
09:30:20 AM...Single APU start

09:35:20 AM...Deorbit ignition (dV: 195.7 mph; dT: 02:38)
09:37:58 AM...Deorbit burn complete (altitude: 214.5 sm)

10:11:00 AM...Entry interface (altitude: 75.6 sm)
10:15:57 AM...1st roll command to right
10:27:46 AM...1st right-to-left roll reversal
10:36:05 AM...Velocity less than mach 2.5 (altitude: 84,700 feet)
10:38:18 AM...Velocity less than mach 1 (altitude: 50,200 feet)
10:38:55 AM...Shuttle banks 269 degrees to line up on runway 33
10:42:35 AM...Landing

FIRST CALIFORNIA OPPORTUNITY: Rev. 204 Deorbit to Edwards Air Force Base, Calif.

10:45:15 AM...MCC 'go' for deorbit burn
10:51:15 AM...MS seat ingress
11:00:15 AM...Single APU start

11:05:15 AM...Deorbit ignition (dV: 195.7 mph; dT: 2:38
11:07:53 AM...Deorbit burn complete (altitude: 213.4 sm)

11:41:01 AM...Entry interface (altitude: 75.6 sm)
11:46:00 AM...1st roll command to left
11:55:55 AM...1st left-to-right roll reversal
12:06:06 PM...Velocity less than mach 2.5 (altitude: 81,800 feet)
12:08:19 PM...Velocity less than mach 1 (altitude: 49,400 feet)
12:09:24 PM...Shuttle banks 205 degrees to line up on runway 22
12:12:31 PM...Landing

SECOND CALIFORNIA OPPORTUNITY: Rev. 205 Deorbit to Edwards

12:21:25 PM...MCC 'go' for deorbit burn
12:27:25 PM...MS seat ingress
12:36:25 PM...Single APU start

12:41:25 PM...Deorbit ignition (dV: 195.7 mph; dT: 02:38)
12:44:03 PM...Deorbit burn complete (altitude: 216.9 sm)

01:16:09 PM...Entry interface (altitude: 75.6 sm)
01:21:06 PM...1st roll command to right
01:32:39 PM...1st right-to-left roll reversal
01:41:10 PM...Velocity less than mach 2.5 (altitude: 82,700 feet)
01:43:25 PM...Velocity less than mach 1 (altitude: 48,800 feet)
01:44:34 PM...Shuttle banks 189 degrees to line up on runway 22
01:47:34 PM...Landing

01:45 PM, 2/19/08, Update: Good weather expected in Florida for Wednesday landing

The Atlantis astronauts checked out the shuttle's re-entry systems today and packed for landing Wednesday at the Kennedy Space Center to close out a successful space station assembly mission. Forecasters are predicting near ideal conditions at the Florida spaceport, with scattered clouds, light winds and good visibility expected.

"The weather forecasts, I've been looking at them almost the last week, the models and the weather forecasts have all been real consistent on what today and tomorrow are going to look like," said entry Flight Director Bryan Lunney. "Today panned out exactly as they said it would and I've got every expectation tomorrow will as well."

He said Atlantis is in good condition and that problems with a heater circuit affecting four small vernier rocket thrusters would have no impact on the shuttle's re-entry. Engineers are equally confident a kinked Freon coolant line in the shuttle's cargo bay will not cause any problems.

Atlantis has enough supplies on board to remain in orbit until Friday in a worst-case scenario. But NASA has activated its backup landing site at Edwards Air Force Base, Calif., in a bid to get the shuttle down Wednesday, on one coast or another, to clear the way for a Navy attempt to shoot down a falling spy satellite.

It's not known when the shoot-down attempt will be made, but amateur satellite trackers monitoring the descent of the crippled NROL-21 satellite say a "notice to airmen," or NOTAM, issued by air traffic control in Honolulu Monday (https://pilotweb.nas.faa.gov/distribution/center.html) establishes a restricted zone west of Hawaii that NROL-21 will pass over Wednesday evening East Coast time. But the NOTAM does not specify the reason for the restricted airspace and the subject line of an email alerting satellite trackers ended with a question mark.

(Editor's note: Interested readers can check the current location of NROL-21 (also known by its orbital designation USA 193) at the Heavens Above web site: http://www.heavens-above.com/orbitdisplay.asp?satid=29651)

Commander Steve Frick and his six crewmates - pilot Alan Poindexter, flight engineer Rex Walheim, Leland Melvin, Stan Love, European Space Agency astronaut Hans Schlegel and returning station flier Dan Tani - have two opportunities on successive orbits to land in Florida Wednesday, followed by two opportunities at Edwards.

The wind is expected to kick up in Florida for the second opportunity, making crosswinds a potential issue, while forecasters are predicting a slight chance of rain within 30 nautical miles of Edwards.

Lunney said the astronauts likely will only have enough water on board for cooling after the cargo bay doors are closed to support three of the four opportunities.

"If in the morning we realize we're only going to have three consecutive opportunities ... we'll assess the weather, and if the weather looks good at KSC, we'll shoot for those first two opportunities with the third being Edwards," Lunney said. "If the weather at KSC goes really bad for us against all the forecasts we've had so opportunities as our backups."

Asked if he was under any pressure to get Atlantis down before the satellite shoot-down attempt, Lunney said "no pressure. I'm not going to land the vehicle until its safe to do so for the crew and we're not going to alter any of our rules because it's not safe. So if the weather's good on Wednesday, we're going to land on Wednesday. If not, then I'll push to Thursday."

Here are the latest deorbit and landing times for Wednesday (in EST/GMT and mission elapsed time):

07:59:54 AM...12...17...14...Deorbit ignition (orbit 202)
09:07:39 AM...12...18...22...Landing at KSC

09:35:20 AM...12...18...50...Deorbit ignition (orbit 203)
10:42:35 AM...12...19...57...Landing at KSC

11:05:15 AM...12...20...20...Deorbit ignition (orbit 204)
12:12:31 PM...12...21...27...Landing at Edwards Air Force Base

12:41:25 PM...12...21...56...Deorbit ignition (orbit 205)
01:47:34 PM...12...23...02...Landing at Edwards Air Force Base

Asked what he thought about the satellite shoot-down effort, Frick said "my first thought when we talked about that was 'go Navy!'"

"But Capt. Poindexter and myself are obviously very excited about the upcoming event they're going to have with the satellite, we're interested to see how it happens," Frick told CNN. "We're not concerned about it, certainly we're going to be safely on the ground and the space station is going to be safely well above the deorbiting satellite. But we'll be interested to watch it and see what happens."

He described the risk of space debris as minimal, to either the shuttle or the space station.

"The only reason we're concerned about the space shuttle is because ... that satellite is below us," he said. "We, of course, have to descend through its altitude on our re-entry. The space station is up at about 185 nautical miles, well above any debris, and once they break the satellite up, the debris is just going to slowly descend ... and drop into the atmosphere and burn up."

Over the course of the mission, the Atlantis astronauts staged three spacewalks, delivered and installed the 26,627-pound European Space Agency Columbus research module, two external experiment packages totaling 1,409 pounds and a fresh tank of high-pressure nitrogen for the station's ammonia cooling system that tipped the scales at 1,.069 pounds.

The shuttle is bringing 2,242 pounds of station hardware back to Earth in its cargo bay, including a spent nitrogen tank and a faulty control moment gyroscope. Some 1,299 pounds of supplies and equipment were transferred from the shuttle cabin to the space station, including a new solar alpha rotary joint drive motor, and 1,343 pounds of equipment was moved from the station to the shuttle's cabin for return to Earth.

The astronauts transferred 1,386 pounds of fresh water to the space station, 95 pounds of oxygen and 27 pounds of nitrogen.

4:45 AM, 2/19/08, Update: Astronauts pack for re-entry, test critical systems; shuttle reoriented to warm thruster with failed heater

The Atlantis astronauts are putting in a busy final day in space today, testing the shuttle's re-entry systems packing up loose gear and rigging the ship for landing Wednesday at the Kennedy Space Center. Forecasters are predicting good weather for the shuttle's return, but NASA plans to staff its backup landing site at Edwards Air Force Base, Calif., in a bid to get Atlantis down, on one coast or the other, before a U.S. Navy attempt to destroy a falling spy satellite.

It's not known when the shoot-down attempt will be made, but amateur satellite trackers monitoring the descent of the crippled NROL-21 satellite say a "notice to airmen," or NOTAM, issued by air traffic control in Honolulu Monday (https://pilotweb.nas.faa.gov/distribution/center.html) establishes a restricted zone west of Hawaii that NROL-21 will pass over around 10:30 p.m. EST Wednesday. But the NOTAM does not specify the reason for the restricted airspace and the subject line of an email alerting satellite trackers ended with a question mark.

(Editor's note: Interested readers can check the current location of NROL-21 (also known by its orbital designation USA 193) at the Heavens Above web site: http://www.heavens-above.com/orbitdisplay.asp?satid=29651)

Shortly after crew wakeup today, commander Steve Frick was asked to re-orient Atlantis, putting the ship's tail toward the sun to provide additional heating to four aft vernier thrusters that lost heater power late Monday due to a circuit failure. One of those thrusters, a left-firing jet on Atlantis' left-side aft rocket pod, dropped to 40 degrees overnight. prompting concern about possible freezing that could damage fuel lines. In a tail-toward-sun orientation, the thruster should stay warm enough to prevent any such damage.

Loss of the aft vernier thrusters will have no impact on the remainder of Atlantis' mission. Due to the redundancy built into the system, the shuttle can use various combinations of thrusters to operate normally in the event of failures.

Space shuttles are equipped with two large orbital maneuvering system - OMS - rocket engines in two pods at the back of the ship that are used to make major orbit changes, including the rocket firing needed to drop the ship back into the atmosphere at the end of a mission.

For smaller changes and adjustments to a shuttle's orientation, 14 reaction control system, or RCS, jets are mounted in the nose, along with two smaller vernier engines. Another 12 primary RCS jets, and two vernier thrusters, are mounted in each aft OMS pod and it is those four aft vernier jets that are affected by the failed heater circuit.

The primary RCS thrusters produce about 870 pounds of push in space while the vernier engines generate a thrust of just 24 pounds each. It's not clear what went wrong with the heater circuit Monday, but flight controllers suspect problems with a so-called "hybrid driver."

The astronauts were awakened around 12:45 a.m. by a recording of Monty Python's "Always Look on the Bright Side of Life" beamed up from mission control in Houston.

"Good morning, Atlantis. A special good morning to you, Steve," astronaut Shannon Lucid called from mission control.

"Good morning, Shannon," Frick replied. "And thanks very much to my wonderful wife Jennifer for that little touch of Monty Python in the morning. We get really busy up here, but it's easy to look at the bright side of life when you look out the window and see the Earth traveling beneath us once every 90 minutes. ... But even with that great view, I think we all believe the bright side of life is when we get home, hopefully tomorrow, and get to see our families."

Lucid then briefed Frick on the result of an overnight investigation into the thruster problem.

"The investigations that we had overnight indicate that a hybrid driver may have failed, resulting the loss of the heater power to the aft vernier thrusters," she said. "So the remainder of the mission will be conducted 'loss of verns.' The propellant margins support all the activities and all planned deorbit opportunities through end of mission plus two (days). Now, there is a potential to perform some unplanned maneuvers and attitude hold in the effort to maintain the aft vernier jets above their non operating limits."

"OK, Shannon, thanks a lot for those words," Frick said. "We kind of figured we'd be down verns from now on. But it's good to hear we don't have any power or prop concerns and I'm glad we have enough prop to fly those attitudes to keep the jets from being a turnaround concern."

He was referring to time lost from work that would be required to fix any fuel line damage after Atlantis returns to Earth. The shuttle's next flight is a high-profile mission in August to service the Hubble Space Telescope.

Here is an updated timeline of today's activity (in EST and mission elapsed time; includes revision M of the NASA television schedule):

EST........DD...HH...MM...EVENT

02/19/08
12:45 AM...11...10...00...Crew wakeup
03:45 AM...11...13...00...Cabin stow
05:10 AM...11...14...25...FCS checkout
06:20 AM...11...15...35...RCS hotfire
06:35 AM...11...15...50...PILOT landing practice
08:05 AM...11...17...20...Deorbit review
08:35 AM...11...17...50...PAO event
08:35 AM...11...17...50...Crew meal
09:35 AM...11...18...50...Cabin stow
12:30 PM...11...21...45...Launch/entry suit checkout
12:30 PM...11...21...45...Mission status briefing on NASA TV
12:45 PM...11...22...00...Ergometer stow
01:15 PM...11...22...30...Recumbent seat setup
01:25 PM...11...22...40...Laptop network teardown
01:35 PM...11...22...50...KU-band antenna stow
04:45 PM...12...02...00...Crew sleep begins
05:00 PM...12...02...15...Daily video highlights reel on NASA TV

6:25 PM, 2/18/08, Update: Engineers troubleshoot vernier thruster heater glitch

Engineers are troubleshooting problem s with heaters used by four of the shuttle Atlantis' aft steering thrusters. Flight controllers noticed problems with one aft vernier thruster - L5L - around 4:30 p.m., at the end of the crew's day. Shortly thereafter, controllers saw similar symptoms with the heaters of three other aft vernier jets. Officials said the problem was not a safety issue and the crew will get up as planned around 12:45 a.m. Tuesday to rig the ship for landing Wednesday.

"The propulsion officer a little over an hour ago noticed a sign that one of those heaters was failing," said NASA mission control commentator Pat Ryan. "Subsequently, heaters for all four of those aft vernier jets have either failed or appear to be failing. It's not an issue for crew safety and, in fact, the team has made the determination that they will not call up any further instructions to the crew, they don't want to disturb them. But the teams will continue working, different disciplines are consulting with one another, trying to run down a cause for these heater failures.

"One late call to the crew, that is to say just after their sleep period (began), was to have commander Steve Frick throw the switch on the flight deck that would cycle those heaters and the propulsion officer has reported no joy in recovering the heaters in that fashion. The heater temperatures are still well above the level where they would pose any threat to that system. But they will be watched overnight by members of the planning team as they work through changes to the upcoming day on orbit for Steve Frick and his six shuttle crewmates."

Space shuttles are equipped with two large orbital maneuvering system - OMS - rocket engines in two pods at the back of the ship that are used to make major orbit changes, including the rocket firing needed to drop the ship back into the atmosphere at the end of a mission.

For smaller changes and adjustments to a shuttle's orientation, 14 reaction control system, or RCS, jets are mounted in the nose, along with two smaller vernier engines. Another 12 primary RCS jets, and two vernier thrusters, are mounted in each aft OMS pod and it is those four aft vernier jets that are affected by the heater problems under discussion in mission control.

The primary RCS thrusters produce about 870 pounds of push in space while the vernier engines generate a thrust of just 24 pounds each. Due to the redundancy built into the system, the shuttle can use various combinations of thrusters to operate normally in the event of failures.

09:10 AM, 2/18/08, Update: Shuttle crew begins final heat shield inspection (UPDATED at 12:05 p.m. with flight director briefing)

The Atlantis astronauts undocked from the international space station today, looped around the outpost to collect spectacular pictures and video and then pulled out ahead of the lab complex before starting a final heat shield inspection to clear the way for re-entry and landing Wednesday.

Using a laser scanner and high-resolution camera on the end of a boom attached to the shuttle's robot arm, the astronauts carried out out a detailed survey of the ship's reinforced carbon carbon nose cap and wing leading edge panels, which experience the most extreme heating during re-entry, to look for any signs of damage that might have occurred since a similar inspection just after launch Feb. 7.

"We cleared Atlantis' heat shield from the flight day two ascent inspections," Flight Director MIke Sarafin said today. "RIght now, we're looking to see if there were any orbital debris impacts along the reinforced carbon carbon. The imagery right now is in the process of being analyzed and we should have an answer from the imagery and engineering experts within the next day."

Nothing obvious could be seen in downlinked video and assuming no problems are found in the analysis, the crew will pack up and test Atlantis' re-entry systems Tuesday before landing Wednesday at the Kennedy Space Center. Entry flight director Bryan Lunney, son on legendary Apollo flight director Glynn Lunney, will discuss NASA's landing strategy Tuesday at a 12:30 p.m. news briefing.

This morning's forecast from the Spaceflight Meteorology Group at the Johnson Space Center in Houston predicts virtually ideal weather at the Kennedy Space Center for the first landing opportunity Wednesday with scattered clouds at 3,000 and 30,000 feet and light winds from the northeast. A slight chance of showers within 30 nautical miles is expected at Edwards Air Force Base, Calif.

"The crew tomorrow will be preparing the cabin for re-entry and just making sure that any stowage items aren't loose during the re-entry timeframe," Sarafin said. "They will prepare a special seat for (returning space station astronaut) Dan (Tani), who has been on station for about four months. ... Tomorrow, the crew will also check out the flight control systems to make sure that they're healthy and there are no problems that occurred over the course of the mission."

The shuttle has enough on-board supplies to stay in orbit until Friday if necessary, officials said. NASA normally would concentrate solely on Florida the first landing day, waving off for 24 hours if bad weather or some other problem forced a delay.

But agency officials announced last week that NASA's backup landing site at Edwards will be staffed Wednesday and for an attempt to get Atlantis down on one coast or the other, weather permitting. NASA said in a statement the strategy is intended to "give the military the biggest possible window and maximum flexibility to ensure the success" of an attempt to shoot down a falling spy satellite.

The National Reconnaissance Office satellite (NROL-21) malfunctioned shortly after launch in December 2006. The out-of-control satellite has been slowly descending ever since and barring intervention, it is expected to plunge back into the thick lower atmosphere early next month.

Because the satellite failed so soon after launch, it is carrying a virtually full load of now-frozen hydrazine rocket fuel, a good portion of which could be expected to reach the ground after a normal atmospheric breakup. The Pentagon last week announced plans to fire a missile at the spacecraft in an attempt to break it apart and disperse the toxic fuel before it can pose a threat.

The Heavens Above website is providing tracking maps showing the satellite's current location based on observations by a network of amateur satellite observers (http://www.heavens-above.com/orbitdisplay.asp?satid=29651):

Atlantis commander Steve Frick and his crewmates will have two opportunities on successive orbits to land in Florida Wednesday and two shots at Edwards Air Force Base in California's Mojave Desert. Here are updated landing times for all four opportunities (in EST/GMT and mission elapsed time):

ORBIT.EVENT...................................DD/HH:MM...EST........GMT

WEDNESDAY, FEBRUARY 20

202...1st KSC OPPORTUNITY DEORBIT BURN........12/17:16...08:01 AM...13:01
203...1st KSC OPPORTUNITY LANDING.............12/18:22...09:07 AM...14:07

203...2nd KSC OPPORTUNITY DEORBIT BURN........12/18:52...09:37 AM...14:37
204...2nd KSC OPPORTUNITY LANDING.............12/19:57...10:42 AM...15:42

204...1st EDW AFB OPPORTUNITY DEORBIT BURN....12/20:22...11:07 AM...16:07
205...1st EDW AFB OPPORTUNITY LANDING.........12/21:27...12:12 PM...17:12

205...2ND EDW AFB OPPORTUNITY DEORBIT BURN....12/21:58...12:43 PM...17:43
206...2ND EDW AFB OPPORTUNITY LANDING.........12/23:02...01:47 PM...18:47

But because of the time required to prepare the shuttle for re-entry, the 90 minutes it takes to go around the world for a second chance and the time needed to back out if entry is delayed for the day, NASA is unlikely to take advantage of all four possible Wednesday landing opportunities.

"A normal day, just to do a deorbit prep and landing is five hours," Sarafin said. "That doesn't account for just standard crew wakeup activities and cabin stow.ÊIf we're going to try multiple attempts, it takes another 90 minutes to go around and if we're going to do three or four orbits, that really does extend the length of the (crew's) day considerably. ... If you still cannot land and you have to back out, open the payload bay doors, turn off all the navigational aids, it does become a significant driver in decision making."

Based on past practice, NASA likely would make two back-to-back attempts to land in Florida and then pick the more favorable of the two Edwards opportunities if the shuttle could not make it back to Kennedy. But if the current forecast holds up, Frick and his crewmates should have a good chance of bringing Atlantis back to Florida as planned.

4:40 AM, 2/18/08, Update: Atlantis undocks from space station

With pilot Alan Poindexter at the controls, the shuttle Atlantis undocked from the international space station today after a successful three-spacewalk assembly mission to attach a new European research lab to the outpost.

"Alpha and Houston, (this is) Atlantis, we have physical separation," an astronaut radioed as the the docking systems disengaged. Following naval tradition, station commander Peggy Whitson rang the ship's bell to signal Atlantis' departure.

Leaving European Space Agency astronaut Leopold Eyharts behind with Whitson and cosmonaut Yuri Malenchenko, Atlantis separated from the space station's forward docking port at 4:24 a.m., about three minutes ahead of schedule. Joining the shuttle crew for the trip home is outgoing station flight engineer Dan Tani, who is wrapping up an extended four-month stay in space.

"We just wanted to thank you again for being a great host and letting us enjoy your station for about a week," shuttle commander Steve Frick radioed Whitson a few minutes before undocking. "We had a great time over there, we learned a lot and we really, really enjoyed working with your crew, one quarter of which we have here and we're happy to take Dan home. But just again, to you and to Yuri and to Leo, thanks very much."

"Well thank you guys," Whitson replied. "it's a great new room you've added on and we really appreciate it. Get Dan home safe, and thanks!"

The flight plan called for Poindexter to guide Atlantis to a point about 400 feet directly in front of the station before looping up, over, behind and underneath the lab complex in a full loop for photo documentation of the station and the new Columbus research module. Back at his starting point, Poindexter plans to depart the area with a rocket firing just after 6 a.m.

As the shuttle drops behind the station, the astronauts will fire up a sensor boom attached to the ship's robot arm for a final inspection of the shuttle's reinforced carbon carbon nose cap and wing leading edge panels to make sure they have not suffered any damage since a similar inspection on the second day of the mission. Today's inspection was scheduled to begin around 8:20 a.m. and end shortly after noon.

"This is a very busy day," said lead flight director Mike Sarafin. "We have the undock and then ... a fly around. Following that, we're going to do our late inspection to ensure that if any orbital debris struck Atlantis during the course of its mission we'll detect it and have the opportunity to determine if it's of critical size before committing to re-entry.

"We'll separate to a safe distance from station, to about 400 feet, we'll perform a series of piloting maneuvers ... up and over the top of the station, all the time they'll be taking imagery of station, back behind station and then underneath completing a full lap. We get back 360 degrees out from where we started and then complete a separation burn to fly up and away from station."

3:30 AM, 2/18/08, Update: Shuttle crew gears up for undocking

As the shuttle Endeavour creeps toward the launch pad in Florida, the Atlantis astronauts, along with outgoing space station flight engineer Dan Tani, are gearing up to undock from the international space station after a successful three-spacewalk assembly mission.

With pilot Alan Poindexter at the controls, undocking is targeted for 4:27 a.m., although the crew has asked permission to depart a few minutes ahead of schedule to improve lighting. Poindexter plans to guide the shuttle through a full loop around the station before leaving the area around 6 a.m.

At the Kennedy Space Center, meanwhile, engineers are hauling Endeavour from the Vehicle Assembly Building to pad 39A, reaching the midpoint of the six-hour trip around 2:30 a.m. Endeavour is targeted for launch March 11 on the next space station assembly mission.

Here is a timeline of today's activities (in EST and mission elapsed time; includes rev. L of the NASA TV schedule):

EST........DD...HH...MM...EVENT

02/18/08
12:45 AM...10...10...00...STS/ISS crew wakeup
02:15 AM...10...11...30...ISS daily planning conference
02:45 AM...10...12...00...Group B computer power up
03:13 AM...10...12...28...Sunrise
03:38 AM...10...12...53...Station in undocking attitude
03:40 AM...10...12...55...Undocking operations begin
03:43 AM...10...12...58...Noon
03:50 AM...10...13...05...Forward port prepped for undocking
03:54 AM...10...13...09...ISS KU antenna parked
04:14 AM...10...13...29...Sunset
04:15 AM...10...13...30...Russian solar arrays feathered
04:20 AM...10...13...35...U.S. solar arrays feathered

04:27 AM...10...13...42...UNDOCKING

04:29 AM...10...13...44...ISS holds attitude
04:32 AM...10...13...47...Range: 50 feet
04:34 AM...10...13...49...Range 75 feet
04:39 AM...10...13...54...Russian arrays resume sun track
04:40 AM...10...13...55...Forward docking port depressurized
04:44 AM...10...13...59...Sunrise
04:56 AM...10...14...11...Range: 400 feet; start fly around
05:06 AM...10...14...21...Range: 600 feet
05:08 AM...10...14...23...Shuttle directly above ISS
05:15 AM...10...14...30...Noon
05:19 AM...10...14...34...Shuttle directly behind ISS
05:31 AM...10...14...46...Shuttle directly below ISS
05:42 AM...10...14...57...Shuttle direcly in front of ISS
05:42 AM...10...14...57...Separation burn No. 1
05:45 AM...10...15...00...Sunset
06:12 AM...10...15...27...Separation burn No. 2
06:15 AM...10...15...30...Sunrise
06:15 AM...10...15...30...Group B computer power down
06:15 AM...10...15...30...Videotape replay of undocking
06:20 AM...10...15...35...Post undocking network reconfiguration
06:50 AM...10...16...05...Crew meal
07:50 AM...10...17...05...Spacesuit installation
08:10 AM...10...17...25...Heat shield sensor boom (OBSS) sensor powerup
08:20 AM...10...17...35...Starboard wing survey
08:20 AM...10...17...35...EVA unpack and stow
08:50 AM...10...18...05...Post-ISS EVA entry preps
10:00 AM...10...19...15...Nose cap survey
11:00 AM...10...20...15...Mission status briefing on NASA TV
11:15 AM...10...20...30...Port wing survey
12:35 PM...10...21...50...OBSS berthing
01:20 PM...10...22...35...Shuttle robot arm (SRMS) powerdown
02:00 PM...10...23...15...Laser scanner downlink
03:30 PM...11...00...45...Post-MMT update on NASA TV
04:30 PM...11...01...45...ISS crew sleep begins
04:45 PM...11...02...00...STS crew sleep begins
05:00 PM...11...02...15...Daily video highlights reel on NASA TV

1:24 PM, 2/17/08, Update: Shuttle astronauts bid station crew farewell

The Atlantis astronauts gathered for a final time aboard the international space station today, bidding the lab crew farewell in a tearful ceremony that marked the end of a complex assembly mission. After one last round of hugs and handshakes, the shuttle crew floated back into Atlantis and hatches were sealed at 1:03 p.m. to set the stage for undocking early Monday.

The brief farewell was particularly poignant for Dan Tani, returning to Earth after an extended four-month stay in space. Originally scheduled to return in December, Tani's stay aloft was extended two months after Atlantis was grounded in December with fuel sensor problems. Along with missing the holidays with his family, Tani was in orbit when his 90-year-old mother was killed in a Dec. 19 car wreck.

"Dan has done a phenomenal job over the last several months," said station commander Peggy Whitson. "He was here a few months more than he had originally planned on, but he's really made up for it and done an incredible job while he was here."

Tani took a moment to describe his impressions of the space station, saying "today I feel very optimistic about our space program and our society because I'm here, I've spent time with a man from France, from Italy and from Germany and from Russia. Nations that have not always been friendly are now cooperating and we're doing great things."

"That was the first thing I was thinking about today," he said. "The other thing I was thinking about today was women, and it's been a very big topic on this flight because when I flew up there were two women commanders and for whatever reason, that was huge news. The unspoken news there was they were both fantastically great commanders and it was a privilege to fly with both of them.

"The other thing I was thinking about today was my mother... my inspiration," Tani said, choking back tears. "And of course, my job is easy compared to my wife's. Jane's the love of my life and she had the hard work while I was having fun. So I can't wait to get back to her and my two little girls.

"If we were in Russia, this would be the third toast - the toast for the women in our lives. I've enjoyed all my time here and I can't wait to get back with all my pictures and videos. So thank you so much for all your help on the ground and really, we couldn't have done it without you. We're doing magnificent things up here and it's not us, of course, we're just the tip. It's the solid foundation everybody on the ground provides for us and makes us look good. Thank you very much."

Tani was replaced aboard the space station by European Space Agency astronaut Leopold Eyharts, who plans to remain aboard the outpost until late March activating and carrying out experiments in Europe's new Columbus research module.

Taking the microphone from Tani, Eyharts said "Dan is a great guy, I've been very impressed by the experience he acquired here in the space station. It was really a pleasure and an honor to receive the handover from him and I hope that in a few weeks, I will be able to do one hundredth of what he is able to do today."

Said Atlantis commander Steve Frick: "For the shuttle crew of Atlantis, STS-122, it was our privilege to bring Leo up to his new home. ... And it's very much our privilege to take Dan home after such a long stay up here and so much hard work. We're looking forward to a very short rest of the flight and a successful landing at the Kennedy Space Center (Wednesday).

"It's been an amazing experience for us," Frick said. "We were very privileged to bring up the European Columbus laboratory module and we're incredibly excited to see it with the lights on and ready for action. So Peggy, thanks very much for being our host. We raced as hard as we could trying to keep up with you and now we need to go take a rest!"

"All right, guys, it's been great having you hear," Whitson replied. The two crews then separated and hatches betwen Atlantis and the station were closed.

The shuttle astronauts are scheduled to go to bed at 4:45 p.m. Wakeup is scheduled for 12:45 a.m. Monday. For readers interested in looking ahead, here is the latest undocking timeline (in EST and mission elapsed time):

EST........DD...HH...MM...EVENT

02/18/08
03:13 AM...10...12...28...Sunrise
03:38 AM...10...12...53...Station in undocking attitude
03:43 AM...10...12...58...Noon
03:54 AM...10...13...09...ISS KU antenna parked
04:14 AM...10...13...29...Sunset
04:15 AM...10...13...30...Russian solar arrays feathered
04:20 AM...10...13...35...U.S. solar arrays feathered

04:27 AM...10...13...42...UNDOCKING

04:29 AM...10...13...44...ISS holds attitude
04:32 AM...10...13...47...Range: 50 feet
04:34 AM...10...13...49...Range 75 feet
04:39 AM...10...13...54...Russian arrays resume sun track
04:44 AM...10...13...59...Sunrise
04:56 AM...10...14...11...Range: 400 feet; start fly around
05:06 AM...10...14...21...Range: 600 feet
05:08 AM...10...14...23...Shuttle directly above ISS
05:15 AM...10...14...30...Noon
05:19 AM...10...14...34...Shuttle directly behind ISS
05:31 AM...10...14...46...Shuttle directly below ISS
05:42 AM...10...14...57...Shuttle direcly in front of ISS
05:42 AM...10...14...57...Separation burn No. 1
05:45 AM...10...15...00...Sunset
06:10 AM...10...15...25...Separation burn No. 2
06:15 AM...10...15...30...Sunrise

"I look forward to some odd things," he added. "I look forward to putting food on a plate and eating several things at once, which you can't do up here. I'm looking forward to spitting my toothpaste out in a sink rather than swallowing it. And of course, the most (significant) thing I'm looking forward to is seeing my (two) girls and my wife."

05:15 AM, 2/17/08, Update: Astronauts wrap up joint operations; farewell ceremony on tap

The Atlantis astronauts and their space station counterparts are wrapping up a final day of joint activity today, hustling to finish supply transfers and activate critical science payloads in the new Columbus lab module before closing hatches between the two spacecraft in preparation for undocking Monday.

A brief farewell ceremony is planned for 12:15 p.m. when station commander Peggy Whitson, cosmonaut Yuri Malenchenko and European Space Agency astronaut Leopold Eyharts will say goodbye to shuttle commander Steve Frick, pilot Alan Poindexter, Leland Melvin, Stan Love, Rex Walheim, Hans Schlegel and outgoing station astronaut Dan Tani.

Tani, launched to the lab complex last October aboard the shuttle Discovery, originally planned to return to Earth in December, but his ride home - Atlantis - was grounded by fuel sensor problems and his stay aloft was extended for two months. As a result, he missed the holidays with his family and was off the planet when his 90-year-old mother was killed in a car wreck Dec. 19.

During today's daily planning conference, flight controllers jokingly observed that Tani would be on the shuttle side of the hatches at the end of the day and reminded him he would still be able to chat with his station crewmates over an audio loop that ties the shuttle, station and flight controllers together.

"Finally for Dan, we know this is your last DPC on board. Kind of brings a tear to your eye," said astronaut Hal Getzelman in space station control. "You'll be on the other side of the hatch here for the evening DPC, but we'll always have the big loop to talk if you just, you know, want to say something."

"Thanks, Hal, and I guess I'll be saying this a lot today, thanks for everybody for making such an exciting and useful couple of months here," Tani said. "I really appreciate the support and the friendship and I can't wait to get back and see everybody. We'll talk to you on the big loop."

"Yeah, that's great, Dan, and no pressure, you don't have to try to outdo the Husker here in the farewell comments and Peggy might have the Kleenex hanging by there for the hatch closure."

Getzelman was referring to the astronaut Tani replaced last year, Nebraska native Clay Anderson, and a tearful farewell ceremony dubbed a "blubberfest" by The New York Times.

Here is a timeline of today's activities (in EST and mission elapsed time; includes rev. K of the NASA TV schedule):

EST........DD...HH...MM...EVENT

02/17/08
01:45 AM...09...11...00...STS/ISS crew wakeup
03:40 AM...09...12...55...ISS daily planning conference
03:45 AM...09...13...00...Flight director update on NASA TV
03:55 AM...09...13...10...Columbus module outfitting continues
05:05 AM...09...14...20...Logistics transfers
06:50 AM...09...16...05...Post-EVA transfers
08:50 AM...09...18...05...Crew meals begin
09:50 AM...09...19...05...Rendezvous tools checkout
09:50 AM...09...19...05...Logistics transfers
10:00 AM...09...19...15...Columbus module 3D photography
11:30 AM...09...20...45...Oxygen system teardown
12:15 PM...09...21...30...Farewell ceremony
12:30 PM...09...21...45...Hatches closed
01:00 PM...09...22...15...Leak checks
01:00 PM...09...22...15...Mission status briefing on NASA TV
01:15 PM...09...22...30...Centerline camera setup
04:15 PM...10...01...30...ISS crew sleep begins
04:45 PM...10...02...00...STS crew sleep begins
05:00 PM...10...02...15...Daily video highlights reel on NASA TV

"We've got a little bit more of that for them to do today," he said. "Specifically, they're going to be setting up the Fluid Science Laboratory and Biolab, continuing to check out the scientific equipment so that we can begin science operations right after undock."

Spencer said the astronauts were virtually done transferring supplies and equipment to and from the station.

"It was 32,000 pounds, of which 27,000 pounds was the Columbus module and then we've got the external payloads that went on it, 2,000 pounds of (shuttle) middeck cargo, which was just resupply of food, clothes, things like that, and of course, a crew member," he said. "There was also 2,000 pounds of cargo transferred from the station to the shuttle on this mission."

With pilot Alan Poindexter at the controls, Atlantis is scheduled to undock at 4:26 a.m. Monday. A photo-documentation flyaround is planned, along with a final inspection of the shuttle's nose cap and wing leading edge panels to make sure they have not suffered any damage since a post-launch inspection.

Weather permitting, Atlantis is scheduled to glide back to Florida early Wednesday, landing at the Kennedy Space Center around 9:06 a.m. to close out an extended 13-day mission.

10:00 AM, 2/16/08, Update: Station, shuttle commanders say satellite shoot-down no threat

The commanders of the shuttle Atlantis and the international space station said today they have no safety concerns about an upcoming attempt to destroy a falling spy satellite. The dramatic shoot-down will be attempted after Atlantis returns to Earth Wednesday and to give the Pentagon as much time as possible, NASA will staff a backup landing site in California in case of problems that might prevent a Florida touchdown.

"We don't have any concerns," shuttle commander Steve Frick told reporters today. "It's obvious to us the DOD and NASA have worked closely together to make sure there are no problems with the plan that they're going to do to make sure the satellite is not a risk to anyone on the ground. We're going to be safely on the ground before they take any action and the satellite is going to be well below the space station, so we don't expect any problems."

The permanently manned space station's orbit was raised an average of one mile today by a 36-minute firing of the shuttle's maneuvering thrusters. The reboost maneuver, one of two needed to set up the proper rendezvous and docking conditions for upcoming visits by the shuttle Endeavour, a European supply ship and a Russian Soyuz spacecraft, left the station in an orbit measuring 215.5 by 203.2 statute miles.

A U.S. Navy cruiser will fire a missile at the falling spy satellite, known as NROL-21, when it reaches an altitude of around 160 miles. A successful strike could blast a few pieces of debris into orbits with high points, or apogees, above the station. But experts say any such debris will rapidly fall back into the atmosphere and that the additional risk to the station is minimal.

"NASA and the DOD loves the station crew as much as they love (the shuttle)," commander Peggy Whitson joked, laughing with her crewmates. "So no, we're not worried about it, either."

Frick said the crews heard about the Pentagon plan "through the normal operational channels," adding the astronauts were informed "in plenty of time and NASA made sure our families found out within that first day of when we found out."

Frick and his crewmates - pilot Alan Poindexter, flight engineer Rex Walheim, Leland Melvin, Stan Love and European Space Agency astronaut Hans Schlegel - will be joined by outgoing space station astronaut Dan Tani for the trip back to Earth. Tani was replaced aboard the station by European Space Agency astronaut Leopold Eyharts, who will remain aboard the lab complex with Whitson and cosmonaut Yuri Malenchenko when Atlantis undocks early Monday.

Tani, launched to the station aboard the shuttle Discovery last October, originally planned to come home in December. But his ride home, Atlantis, was grounded by fuel sensor problems and his stay in space was extended two months. Along with missing the holidays with his family, Tani was in orbit when his mother was killed in a Dec. 19 car accident.

Tani said today he is preparing notes that might help future long-duration space fliers cope with personal tragedies, as well as nuts-and-bolts advice about living and working in space, tips on "what I think people on the space station might think about if they have a family tragedy similar to what I had, more administrative kind of stuff, things I think will help them communicate with their family more."

"So I am sort of developing some advice that I will leave up here," he said. "But it's mainly how to maximize communications with the ground and that kind of thing. ... And certainly, I'll talk to our office about it when I get home."

On a lighter note, Tani said he's had a great time in space and that he will leave the station with mixed emotions.

"I love living here on the station, it's comfortable, it's fun, it's exciting, the view, of course," he said. "So it's going to be tough leaving here, but obviously, I want to get back to see my family.

"I look forward to some odd things," he added. "I look forward to putting food on a plate and eating several things at once, which you can't do up here. I'm looking forward to spitting my toothpaste out in a sink rather than swallowing it. And of course, the most (significant) thing I'm looking forward to is seeing my (two) girls and my wife."

06:15 AM, 2/16/08, Update: Station reboost, crew news conference on tap

The Atlantis astronauts and their space station crewmates are working through an extension day in orbit today, concentrating on work to activate the European Columbus science laboratory. Atlantis commander Steve Frick plans to oversee a reboost operation this morning, firing Atlantis' rocket thrusters to increase the station's altitude, and the combined crews will hold a joint news conference at 8:40 a.m. to discuss the progress of the flight.

"As you can expect, anytime you move to a new location or, in this case, the new location is added to your existing home, you've got a lot of unpacking to do," said space station Flight Director Ron Spencer. "In this case, a lot of that is science equipment (in the Columbus module). So the crew is still setting up the science equipment and checking out the instruments, making sure the computers can command to the instruments and that they function properly in anticipation of firing these up for science activities as soon as the shuttle leaves.

Atlantis' mission was extended two days, once to replan a spacewalk and then to give the crew additional time to commission Columbus. Today is the second extension day and the crew will spend part of its day setting up science racks in the new lab module.

"These activities were scheduled for next week after the shuttle had left, so we're getting significantly ahead in the timeline," Spencer said. "They should be able to start doing science operations a lot earlier than we'd originally planned inside the Columbus module. So even though we added two extra days to the mission, we're really getting a lot more ... because of the fast pace of the crew's work."

In addition to the Columbus outfitting, the shuttle crew plans to fire Atlantis' rocket thrusters for 36 minutes starting just before 7:20 a.m. to boost the station's altitude.

"We're also going to transfer some of the extra oxygen from the space shuttle to the space station to help fill up our tanks so that we can support additional spacewalks after the shuttle leaves," Spencer said.

Here is an updated timeline of today's activity (in EST and mission elapsed time; includes revision J of the NASA television schedule):

EST........DD...HH...MM...EVENT

02/16/08
02:45 AM...08...12...00...Crew wakeup
04:45 AM...08...14...00...ISS daily planning conference
05:00 AM...08...14...15...Columbus outfitting continues
05:15 AM...08...14...30...Flight director update on NASA TV
05:55 AM...08...15...10...Spacewalk tools deconfigured
07:16 AM...08...16...31...Reboost operations
08:40 AM...08...17...55...Crew news conference
09:20 AM...08...18...35...Joint crew photo
09:40 AM...08...18...55...Logistics transfers
09:40 AM...08...18...55...Post-spacewalk transfers
10:00 AM...08...19...15...Crew conference replay with translation
10:50 AM...08...20...05...Joint crew meal
11:50 AM...08...21...05...Logistics transfers
11:50 AM...08...21...05...Crew off-duty time begins
01:00 PM...08...22...15...Mission status briefing on NASA TV
05:15 PM...09...02...30...ISS crew sleep begins
05:45 PM...09...03...00...STS crew sleep begins
06:00 PM...09...03...15...Daily video highlights reel on NASA TV

"It may seem like everything's weightless up there in space and it'll stay up there forever, but really there's still (atmospheric) drag going on and over many months, the space station's orbit ends up getting lower and lower," Spencer said. "And so we have to reboost it occasionally to keep it in orbit.

"So a lot of the shuttle missions, we'll take advantage of their extra gas before they leave to do that and then when the shuttle's not there, we'll use the Russian propellant to do that. But we like to save as much of that as possible, so we make use of the shuttle's extra resources. That's what we're doing today."

Atmospheric drag is responsible for the slow decay of the orbit of a crippled U.S. spy satellite that is plunging back to Earth. The U.S. Navy is finalizing plans to fire a missile at the satellite in an attempt to break it up and disperse its load of toxic hydrazine rocket fuel to prevent any possible ground contamination.

The dramatic shoot-down will not be attempted until after Atlantis lands. The shuttle is scheduled to return to Florida on Wednesday and NASA officials announced Friday that the agency also will staff its backup landing site at Edwards Air Force Base, Calif., to "ensure we land at the earliest opportunity. The reason is to give the military the biggest possible window and maximum flexibility to ensure the success of the satellite intercept."

7:30 PM, 2/15/08, Update: NASA will activate Florida, California landing sites to ensure shuttle return before satellite shoot down

The shuttle Atlantis is scheduled to land Wednesday at the Kennedy Space Center in Florida but NASA officials said today they will staff the agency's backup landing site in California to get the shuttle down as soon as possible and "give the military the biggest possible window" for destroying a falling satellite.

Pentagon planners are fine tuning plans to fire a missile from a Navy cruiser in the Pacific Ocean in a bid to break up the crippled NROL-21 satellite, which malfunctioned shortly after launch in December 2006. The out-of-control satellite has been slowly descending ever since and barring intervention, it is expected to plunge back into the thick lower atmosphere early next month.

Because the satellite failed so soon after launch, it is carrying a virtually full load of now-frozen hydrazine rocket fuel, a good portion of which could be expected to reach the ground after a normal atmospheric breakup. The Pentagon announced plans Thursday to fire a missile at the spacecraft in an attempt to break it apart and disperse the toxic fuel before it can pose a threat.

Marine Gen. James Cartwright, vice chairman of the Joint Chiefs of Staff, said Thursday the unprecedented intercept would not be attempted until after Atlantis returns to Earth on Wednesday to minimize the risk of debris that might pose a threat to the orbiter.

Normally, NASA would not staff its backup landing site at Edwards Air Force Base, Calif., for the shuttle's first landing attempt. If the weather or some other problem prevented a Florida landing, the crew would simply remain in orbit another 24 hours and try again the next day. In that case, Edwards would be an option.

But space station Flight Director Sally Davis today read a prepared statement during an afternoon briefing saying Edwards will be staffed for the first landing attempt Wednesday.

"The shuttle is scheduled to land on Feb. 20," she said. "We're going to open up Dryden (Flight Research Center) at Edwards Air Force Base to ensure we land at the earliest opportunity. The reason is to give the military the biggest possible window and maximum flexibility to ensure the success of the satellite intercept."

It typically costs nearly $2 million to service a shuttle at Edwards and ferry it back to the Kennedy Space Center atop a 747 jumbo jet. It also adds a week or more to the time necessary to prepare a shuttle for its next flight.

But NASA managers are hopeful it won't come to that. The preliminary long-range forecast for Wednesday calls for acceptable conditions in Florida and the crew will have two shots at Kennedy on successive orbits before any diversion to Edwards. NASA's second alternate landing site near White Sands, N.M., will not be staffed.

Atlantis, currently docked to the international space station, is in a roughly circular orbit at an altitude of about 210 miles. Pentagon planners want to hit the falling satellite at an altitude of about 160 miles. Depending on the timing of the shot and the relative positions of the spacecraft, the shuttle could interfere with those plans or be exposed to potentially dangerous debris if the ship was still in orbit.

A landing Wednesday would take the shuttle out of the equation and give military planners a longer window to deal with the errant satellite.

The space station, NASA officials say, is not in any danger. While a successful strike would create a cloud of debris, including some that might reach or exceed the station's altitude, most of it would quickly re-enter and burn up.

"We've analyzed it and it has negligible additional risk to the space station," said Kirk Shireman, deputy space station program manager at the Johnson Space Center in Houston. "So we're not concerned at all about any risk to the space station and at this point in time have no plans to do any operations in conjunction with that activity."

4:00 PM, 2/15/08, Update: Spacewalk ends; all major objectives accomplished

Astronauts Rex Walheim and Stan Love completed a seven-hour 25-minute spacewalk today, installing two experiment packages on the space station's new Columbus research module and moving a faulty gyroscope back to the shuttle Atlantis for return to Earth.

With the primary objectives of the excursion successfully accomplished, the astronauts took a moment to carry out a "roughness test" on an astronaut handrail that runs around the Quest airlock's main hatch. Love reported during a spacewalk Monday that he had noticed a small crater, possibly due to impact with space debris, in the handrail.

Over the past several months, flight controllers have been concerned about small tears in the gloves used by spacewalkers, apparently caused by rubbing across a rough surface somewhere on the station. As a precaution, all spacewalking astronauts now pause periodically to inspect their gloves and wear bulky overgloves, when possible, as an additional precaution.

To find out if "Love crater" might be responsible for at least some of the previous glove damage, Walheim and Love rubbed an improvised tool across the damage site featuring a spare suit glove wrapped around a socket wrench.

Veteran spacewalker Jerry Ross, in mission control at the Johnson Space Center in Houston, told Walheim to "draw it across the crater site to see if you're getting any significant snaring or tearing ... as you do it."

"I can feel a little bit of rough," Walheim reported. "It's not really grabbing or anything. It is rough. ... I can feel a little bit of snagging as it moves across, I think. Everything else is smooth until you get there."

But he said he could not see any noticeable damage to the glove material on the tool. He then pressed on the crater with his index finger, while wearing an overglove, but reported, "nothing, Jerry."

"OK, copy, you didn't see or necessarily feel much of anything?"

"No."

He then tried a variety of other techniques, rubbing various parts of the glove across the damage site but was unable to generate any noticeable damage.

By the time they had finished the glove tests, the astronauts were well beyond the planned six-and-a-half-hour duration planned for today's spacewalk. They opted not to press ahead with a "get-ahead" inspection of the station's right side solar array rotary joint, a decision flight controllers seconded.

While the astronauts were mostly business as they worked through their busy flight plan, they paused a few times to marvel at the view.

"Now there's San Francisco, Oh!" Walheim exclaimed as the shuttle-station complex passed 210 miles above the California coast. "San Francisco, Monterey, all the way down to LA, up the state. I finally get to see San Francisco from EVA (a spacewalk). ... Wow, what a way to come over the West Coast. Oh my goodness!"

"Wow," Love said.

"Isn't that amazing?" Walheim exclaimed. "See the bridges? Berkeley? I can see San Carlos where I grew up. Absolutely amazing!"

8:30 AM, 2/15/08, Update: Spacewalk begins

Astronauts Rex Walheim and Stan Love switched their spacesuits to battery power at 08:07 a.m. to officially kick off a planned six-and-a-half-hour spacewalk. The first item on the agenda today is to move a sun-monitoring instrument from the shuttle Atlantis' cargo bay to a mounting fixture on the hull of the new Columbus research module. Once the SOLAR instrument is in place, Walheim and Love will move a failed space station gyroscope back to the shuttle for return to Earth and then haul another science package, known by the acronym EuTEF, to Columbus.

Here is an updated timeline for today's spacewalk based on the actual start time (in EST and event elapsed time):

EST........HH...MM...EVENT

08:07 AM...00...00...EVA-3: Spacesuits to battery power
08:12 AM...00...05...EVA-3: Airlock egress
08:22 AM...00...15...EVA-3: SOLAR transfer from shuttle to Columbus
11:02 AM...02...55...EVA-3: Gyro transfer to shuttle
12:17 PM...04...10...EVA-3: EuTEF transfer from shuttle to Columbus
01:52 PM...05...45...EVA-3: Cleanup and ingress
02:32 PM...06...25...EVA-3: Airlock repressurization

05:30 AM, 2/15/08, Update: Astronauts suit up for final spacewalk

Astronauts Rex Walheim and Stan Love are gearing up for a third and final spacewalk today, a planned six-and-a-half-hour excursion to mount a pair of science packages on the hull of the new Columbus research module and to move a faulty space station gyroscope to the shuttle Atlantis for return to Earth.

The spacewalk, the 104th devoted to station assembly and maintenance since construction began in 1998, is scheduled to start around 8:40 a.m. when Walheim and Love, floating in the Quest airlock module, switch their spacesuits to battery power.

"The three main goals are to bring the two exposed payloads that the Europeans want on the outside of Columbus and attach them to Columbus," Walheim said in a NASA interview. "Also, we're going to bring back a control moment gyro, or a CMG, that had failed earlier in the space station program. (An earlier crew) replaced it, so there's a new one that's working, but we have to take the failed one back home.

"Stan's going to have quite the (robot) arm rides around taking these payloads back and forth, and I'm going to assist him."

If time is available at the end of the spacewalk, the astronauts plan to rub an improvised tool featuring a spacesuit glove wrapped around a socket wrench across a small impact crater seen earlier on an airlock handrail. The goal is to find out if rough edges around the tiny crater could be responsible for glove damage noted during recent spacewalks.

One other possible "get-ahead" task involves a quick inspection of the station's right side solar alpha rotary joint, or SARJ, one of two that rotate outboard solar arrays to track the sun. The starboard SARJ has been shut down since late last year because of excessive vibration and internal contamination. If time is available today, Love and Walheim will inspect and photograph an area of the 10-foot-wide bearing race ring where engineers have spotted what appears to be a small defect.

It's not clear whether the defect might be a tiny crater or the result of some sort of debris resting on the surface of the race ring.

Here is a timeline of today's activity (in EST and mission elapsed time; includes revision I of the NASA television schedule):

EST........DD...HH...MM...EVENT

02/15/08
03:45 AM...07...13...00...STS/ISS crew wakeup
04:20 AM...07...13...35...EVA-3: Airlock repress to 14.7 psi
05:15 AM...07...14...30...Flight director update on NASA TV
05:30 AM...07...14...45...EVA-3: Airlock campout preps
05:35 AM...07...14...50...Space station daily planning conference
06:00 AM...07...15...15...Columbus module activation continues
07:00 AM...07...16...15...EVA-3: Spacesuit purge
07:15 AM...07...16...30...EVA-3: Spacesuit oxygen pre-breathe
08:05 AM...07...17...20...EVA-3: Airlock depressurization
08:35 AM...07...17...50...EVA-3: Spacesuits to battery power (spacewalk begins)
08:40 AM...07...17...55...EVA-3: Airlock egress
08:55 AM...07...18...10...EVA-3: SOLAR transfer from shuttle to Columbus
11:10 AM...07...20...25...Crew meals begin
11:35 AM...07...20...50...EVA-3: Gyroscope transfer to shuttle
12:50 PM...07...22...05...EVA-3: EUTEF transfer from shuttle to Columbus
02:25 PM...07...23...40...EVA-3: Cleanup and ingress
03:05 PM...08...00...20...EVA-3: Airlock repressurization
03:15 PM...08...00...30...Spacesuit servicing
04:30 PM...08...01...45...Mission status briefing on NASA TV
06:15 PM...08...03...30...Station crew sleep begins
06:45 PM...08...04...00...Shuttle crew sleep begins
07:00 PM...08...04...15...Daily video highlights reel on NASA TV

"First will be SOLAR, which is a solar telescope that mounts on the outside of Columbus. It's like a little satellite ... but it gets its attitude control, its power and its data feed all through the space station, so it's a little satellite that mounts on the outside of space station. We will pick it up from the payload bay, there's one bolt that holds it in place, then riding the arm I will carry it up to Columbus. Once it's bolted in place - and driving that bolt connects all its power and data connections all at the same time - we'll back away."

The SOLAR instrument package will be mounted on the upper of two attachment platforms on the outboard bulkhead of the Columbus module. At that point, the station arm will move Love to an external storage platform near the Quest airlock so he and Walheim can move the faulty gyroscope back to Atlantis for return to Earth.

"The space station holds its attitude in space using big, heavy gyroscopes and over the history of station we've had two of these fail," Love said. "The STS-118 crew removed the CMG-3, the CMG of interest here, and put it on a platform for us; we're bringing it home. So we'll go over by the airlock, grab that CMG, unbolt it, the arm will swing me over to the shuttle payload bay and we'll plunk it down in the exact same slot that we pulled SOLAR out of because it's the same structural interface there."

The space station uses four 500-pound control moment gyros to change its orientation in space without having to fire rocket thrusters. The devices are critical to space station operations and NASA wants to get the failed unit back to Earth so engineers can figure out what went wrong.

"Stan will come underneath that stowage platform and we'll remove some of the insulation that's around it so he can grab onto some handrails. Then I'll do the bolt and release it and then he can take it off back to the payload bay. When he gets a ride to the payload bay, I'll go scurry down there, free-floating as we call it - basically just walk with my hands - and get down there and help him put it back on the space shuttleÕs carrier so that we can bring it home."

With the CMG safely bolted down in the shuttle's cargo bay, "we'll move over to EuTEF (the European Technology Exposure Facility), which is an external exposure facility, basically, looking at how materials respond to being exposed to space for a long period of time; another little satellite that mounts on the outside of Columbus," Love said. "I'll pick it up, we'll unbolt it, we'll drag it up, riding the arm, up to Columbus and stick it on another External Payload Facility, bolt it in place, and then our EVA is done."

The EuTEF package will be mounted on Columbus' lower external attachment bracket.

"We have some cleanup work - we have to move the toe clip off the arm, we're not allowed to leave it there; we have some safety tethers that we had strung on previous EVAs, we have to clean all that up since it's the last EVA of the flight. If there's any extra time we may do extra tasks."

6:20 AM, 2/14/08, Update: 'Love Crater,' starboard SARJ inspections added to Friday spacewalk (UPDATED at 7 a.m. with SARJ problem resolution)

The Atlantis astronauts are working through a relatively light day today, continuing work to outfit and activate the European Columbus research module before enjoying a few hours of off-duty time. Early today, European flight controllers told the crew they had successfully completed initial activation with the module's computer systems. Later this morning, the astronauts will get a call from German Chancellor Angela Merkel at 9:55 a.m. and field questions from reporters at 11:15 a.m.

Flight controllers at the Johnson Space Center in Houston told space station commander Peggy Whitson early today that the station's left-side solar alpha rotary joint, or SARJ, had unexpectedly shut down. The station is equipped with two SARJ joints to turn outboard solar arrays to keep them face on to the sun. For the past few months, engineers have been troubleshooting a mysterious problem in the right-side SARJ that has higher-than-normal vibration and internal metallic contamination.

The port SARJ has been working normally and today's shutdown was related to computer commanding to lock the port-side solar arrays in place before a space shuttle water dump. By 7 a.m., the problem had been resolved and the arrays were properly positioned.

Atlantis astronauts Rex Walheim and Stan Love plan to carry out a third and final spacewalk Friday to install two science packages on the outboard hull of the Columbus module. They also plan to move a faulty space station gyroscope back to Atlantis for return to Earth and pre-position tools needed by the next shuttle assembly crew.

Flight controllers have now added two additional "get-ahead" tasks to the spacewalk if time is available: An additional inspection of the starboard SARJ and a test to find out if damage seen on a handrail Monday by Love - and now dubbed "Love Crater" - might be responsible for recently observed damage to spacesuit gloves.

For the SARJ inspection, the astronauts will photograph a specific point on the 10-foot-wide bearing race ring where engineers studying previous photographs have spotted what might be a small impact crater or defect. The astronauts will photograph the site from different angles to help engineers assemble a three-dimensional image.

"What we've seen in some of the pictures is another damage point we want a closer look at," said Flight Director Ron Spencer. "So if we get time, we'll have the crew go out there and remove one of the covers in a specific area and take some more pictures of this one particular area of potential damage."

In photographs uplinked to the crew as part of the daily "execute package" of flight plan revisions, notes and instructions, the damage site appears as a small light-colored dot on one side of the race ring. It is not clear whether the point of interest is a defect in the metal of the race ring or some sort of contamination resting on the surface.

For the handrail inspection, the astronauts will use a spare spacesuit overglove wrapped around a wrench handle and rub it over the damage site to see if it causes the sort of tears in a protective covering that has been noted in recent spacewalks. The handrail circles the outer hatch of the Quest airlock module and as such is frequently handled by astronauts.

"On EVA-1 when they were coming in at the end of their EVA, they noticed a possible micrometeoroid damage on one of the handrails that is the primary translation path out of the airlock," Spencer said. "So today, we're going to have the crew build this little tool, which is the use of an EVA overglove and a socket. The crew's going to go out there and rub this against that handrail and see if it causes any damage on the glove, to see if this is the cause of some of the glove problems we've been having lately."

Here is an updated timeline of today's activity (in EST and mission elapsed time; includes revision F of the NASA television schedule):

EDT........DD...HH...MM...EVENT

02/14/08
03:45 AM...06...13...00...STS/ISS crew wakeup
05:15 AM...06...14...30...Flight director's update on NASA TV
05:25 AM...06...14...40...ISS daily planning conference
05:50 AM...06...15...05...Columbus module outfitting/activation
07:10 AM...06...16...25...Logistics transfers
08:25 AM...06...17...40...Spacesuit swap
09:15 AM...06...18...30...Equipment lock preps
09:55 AM...06...19...10...ESA PAO event with German chancellor
10:00 AM...06...19...15...Crew meals begin
11:00 AM...06...20...15...Shuttle crew off duty (staggered)
11:15 AM...06...20...30...PAO event (NBC News, WOI-TV, WBBM)
02:30 PM...06...23...45...Mission status briefing on NASA TV
03:45 PM...07...01...00...EVA-3: Procedures review
06:00 PM...07...03...15...EVA-3: Mask pre-breathe for campout
06:55 PM...07...04...10...EVA-3: Campout begins (10.2 psi depress)
07:15 PM...07...04...30...ISS crew sleep begins
07:45 PM...07...05...00...STS crew sleep begins
08:00 PM...07...05...15...Daily video highlights reel on NASA TV

04:45 PM, 2/13/08, Update: Spacewalk ends; mission extended one day (UPDATED at 6:30 p.m. with resolution of computer glitch; landing time update)

Astronauts Rex Walheim and Hans Schlegel staged a successful six-hour 45-minute spacewalk today, replacing a nitrogen tank needed to maintain pressure in the space station's ammonia cooling system. Mission managers, meanwhile, officially gave the shuttle Atlantis' heat shield a clean bill of health and decided to extend the mission one more day to give the crew additional time to activate the new Columbus research module. The extra day will be inserted Saturday with landing now targeted for around 9:06 a.m. on Feb. 20.

"Steve, a number of things to tell you here, all good news," astronaut Steve Robinson radioed shuttle commander Steve Frick from mission control in Houston. "Based on the inspection we've had so far, and all the other types of imagery, Atlantis' thermal protection system is currently cleared for entry. The programs came together and decided to add an additional one-day extension to your mission. ... You do have sufficient (carbon dioxide-absorbing lithium hydroxide) aboard the ship. We'll have to be checking on food, we're having our folks check on what was stowed, but we're going to need your input on that. We are looking forward to an O2 (oxygen) transfer (to the station), probably on flight day nine."

"Thanks very much for the big picture," Frick replied. "Great news, certainly we look forward to another day on the space station and happy to do whatever works best for the station and the station crew to put them in a good position when we leave. ... That's great news, we appreciate the heads up and also the good news that our TPS (thermal protection system) has been cleared for entry."

"That's exactly the intent of staying up an extra day, is getting Columbus that good head start with a trained crew," Robinson said.

The new Columbus module was attached to the space station Monday and within hours, European Space Agency engineers began working through a complex activation process. But they quickly ran into problems uplinking commands through the station's U.S. command and control system and into the computers inside Columbus. Late today, U.S. and European flight controllers decided the problem likely involved "stale commands" in a queue used by the station's primary U.S. computer system.

To flush out the queue, controllers shifted the active U.S. computer system into standby mode and designated a backup system as primary. Just before 6 p.m., engineers reported success, saying they finally were able to command the European computer systems. The Columbus activation process, which had been on hold, resumed but engineers decided to suspend the work overnight while the astronauts slept in case of any additional problems that might disturb their sleep or require their attention.

During today's spacewalk, Walheim and Schlegel successfully replaced a 550-pound nitrogen tank on the international space station's main solar power truss, installed four thermal covers on the keel pins used to secure the Columbus module in the shuttle's cargo bay for launch and worked to tie down micrometeoroid shields on the U.S. Destiny lab module. There were no problems of any significance and Schlegel, a German astronaut who became ill earlier in the mission and had to sit out a spacewalk Monday, appeared to have no problems today.

"It was great working with you today, you guys did an outstanding job," shuttle pilot Alan Poindexter, the spacewalk coordinator, radioed as Walheim and Schlegel returned to the station's airlock. "It really was a pleasure working with you."

"Awesome job, Dex, thanks for all the help," Walheim replied. "And thanks to the ground for all of our prepearion to get this done. It was really a great help in the execution."

This was the 103rd spacewalk devoted to station assembly and maintenance since construction began in 1998, the fourth for Walheim and the first for Schlegel. Total station EVA time now stands at 646 hours and 18 minutes with Walheim's cumulative total increasing to 28 hours and 58 minutes.

Walheim and astronaut Stan Love plan to stage a third and final spacewalk Friday to attach external instruments to the Columbus module and to move a faulty space station gyroscope back to Atlantis for return to Earth.

9:30 AM, 2/13/08, Update: Spacewalk begins

Astronauts Rex Walheim and Hans Schlegel switched their spacesuits to internal battery power at 9:27 a.m. to officially begin a planned six-and-a-half-hour spacewalk to replace a high-pressure nitrogen tank on the international space station's main solar power truss.

Here is a revised timeline for today's spacewalk based on the actual start time (in EST and event elapsed time):

EST........DD...HH...EVENT

09:27 AM...00...00...EVA-2: Spacesuits to battery power
09:32 AM...00...05...EVA-2: Airlock egress
09:32 AM...00...05...Station robot arm (SSRMS) ready to support
09:47 AM...00...20...EVA-2: New nitrogen tank removal from payload bay
11:37 AM...02...10...EVA-2: Nitrogen tank installation on P1 truss
01:42 PM...04...15...EVA-2: Old nitrogen tank stowed in payload bay
03:22 PM...05...55...EVA-2: Cleanup and airlock ingress
03:57 PM...06...30...EVA-2: Airlock repressurization

http://www.cbsnews.com/network/news/space/currentglance.html

Readers interested in checking the space station's current location are encouraged to check out this interesting page:

http://www.lizard-tail.com/isana/lab/googlesat/googlesat2.php

7:00 AM, 2/13/08, Update: Walheim, Schlegel suit up for spacewalk

Astronauts Rex Walheim and Hans Schlegel are suiting up for a planned six-and-a-half-hour spacewalk today to swap out a 550-pound nitrogen tank used to push ammonia through the station's main cooling system during start up.

Walheim, anchored to the end of the space station's robot arm, will carry the new tank, about the size of a small refrigerator, from the shuttle Atlantis' cargo bay up to the left side of the station's main solar power truss. He and Schlegel will temporarily mount the tank on an attachment fitting, remove the old tank and "temp stow" it to one side. After installing the new tank and hooking up electrical cables and flex hoses, Walheim will carry the old unit back to the shuttle for return to Earth.

Today's spacewalk is the 103rd devoted to space station assembly and maintenance since construction began in 1998. It is the fourth EVA for Walheim and the first for Schlegel, a 56-year-old father of seven who became ill earlier in the mission. He had to sit out a spacewalk Monday to prepare the new Columbus module for installation but he said Tuesday he was ready to go for the second excursion.

"I feel really great right now," he said. "I'm, of course, a little bit anxious because (this) will be my first EVA."

Here is an updated timeline of today's activity (in EST and mission elapsed time; includes revision E of the NASA television schedule):

EDT........DD...HH...MM...EVENT

02/13/08
04:45 AM...05...14...00...STS/ISS crew wakeup
05:20 AM...05...14...35...EVA-2: Airlock repressurized for hygiene break
06:15 AM...05...15...30...Flight director's update on NASA TV
06:30 AM...05...15...45...EVA-2: Airlock depress to 10.2 psi
06:35 AM...05...15...50...ISS daily planning conference
06:55 AM...05...16...10...Columbus outfitting continues
08:00 AM...05...17...15...EVA-2: Spacesuit purge
08:15 AM...05...17...30...EVA-2: Spacesuit oxygen pre-breathe
08:25 AM...05...17...40...Columbus SSC activation
09:05 AM...05...18...20...EVA-2: Airlock depressurization to vacuum
09:35 AM...05...18...50...EVA-2: Spacesuits to battery power (begins spacewalk)
09:40 AM...05...18...55...EVA-2: Airlock egress
09:40 AM...05...18...55...Station robot arm (SSRMS) supports
09:55 AM...05...19...10...EVA-2: Nitrogen tank removal from payload bay
11:15 AM...05...20...30...Crew meals begin
11:45 AM...05...21...00...EVA-2: Nitrogen tank installation on P1 truss
01:50 PM...05...23...05...EVA-2: Old nitrogen tank stowed in payload bay
03:30 PM...06...00...45...EVA-2: Cleanup and airlock ingress
04:05 PM...06...01...20...EVA-2: Airlock repressurization
04:15 PM...06...01...30...Spacesuit servicing
05:30 PM...06...01...45...Mission status briefing on NASA TV
05:35 PM...06...02...50...EVA-3: Tool prep
07:15 PM...06...04...30...ISS crew sleep begins
07:45 PM...06...05...00...STS crew sleep begins
08:00 PM...06...05...15...Daily video highlights reel

"Today, the crew's going to be moving some of the racks from their launch locations to the permanent location in the module and continuing to move other equipment," said station Flight Director Ron Spencer. "On the ground commanding side, we're a little bit behind. We had a problem yesterday commanding to some of the computers inside the Columbus module and we're still trying to work through those problems and determine what the cause is and figure a solution. So right now, we're about two-and-a-half hours behind on the ground commanding side from what we expected to have finished yesterday. But the crew is way ahead."

Walheim and Schlegel spent the night inside the Quest airlock module at a reduced pressure of 10.2 pounds per square inch. The so-called "camp out" helps purge nitrogen from the bloodstream and prevent the bends after working in NASA's low-pressure spacesuits. If all goes well, the astronauts will switch their suits to battery power around 9:35 a.m. to officially begin today's spacewalk.

"It sounds so simple, just exchange a nitrogen tank," Schlegel said in a NASA interview. "(But) itÕs about a yard times a yard times one and a half yards, and the weight is roughly 500 pounds. ItÕs quite a heavy thing. You cannot just put it on your back and move and get it there. ... The installation includes mechanical connections, electrical connections and then nitrogen (lines), highly pressurized, and after that, you have to close thermal covers to keep it protected from thermal influences by the environment."

The nitrogen tank assembly, or NTA, is loaded with about 80 pounds of nitrogen pressurized to 2,500 pounds per square inch. After exiting the airlock, Walheim and Schlegel will make their way over to the shuttle's cargo bay. Leland Melvin and Stan Love, working at a robotics control station inside the Destiny laboratory module, will operate the station's robot arm.

"I will get the arm ready to ride and then jump in and basically clip my heels into the robot arm," Walheim said in a NASA interview. "Leland and Stan will have a chance to drive me around to my work site. My first work site is in the payload bay where I'll take the brand-new nitrogen tank and extract it from the payload bay ... and then we'll take it out to the P1 (port 1) truss where we're going to swap it out.

"We'll put it on a ballstack, which basically holds it in place, and then ... we'll pull out the empty nitrogen tank. I'll pull that out on the arm and then we'll temp-stow that one, also on a ballstack. So we'll have the two of them basically temporary stowed. Then I go back and grab the new one and put it into the truss and then we can start doing the electrical and nitrogen connections in the front and the back of that tank. Once I'm done with that, I take the empty nitrogen tank and we put it back in the shuttle payload bay so we can bring it back home and use it again."

Asked about the difficulty of manually carrying a 550-pound component, Walheim said "it's not too hard. I've found in space things are fairly stable when you hold on to them, especially if they're big, a large mass, you know, several hundred pounds, up to over a thousand pounds. They're fairly stable.

"If you want to get them moving, you just give them a little bit of force and they start moving, but then you've got to stop them, too," he said. "So the main thing is just to hold them loosely - a loose grip, don't over control them - and just hang on and be aware when you're starting and stopping on the arm."

If time is available today, the astronauts will place thermal covers over the keel pins that held the Columbus module in Atlantis' cargo bay during launch.

6:15 PM, 2/12/08, Update: Schlegel 'anxious' about spacewalk Wednesday; won't discuss illness but says he's good to go

German astronaut Hans Schlegel, a 56-year-old father of seven who was replaced on a spacewalk Monday because of an undisclosed medical problem, told CBS News today he's feeling fit and ready for a spacewalk Wednesday to service the space station's cooling system.

In an interview that was scheduled before launch, Schlegel, Atlantis commander Steve Frick and pilot Alan Poindexter said they were pleased with the progress of the mission and the successful installation of the European Columbus research module Monday, a day later than planned because of Schlegel's illness.

"It's been an interesting mission," Frick said from the shuttle's flight deck. "Every flight always seems to offer new challenges, it never goes quite the way you plan it. But I've been really happy and excited we were able to do a little replan and still get EVA-1 (spacewalk No. 1) off very successfully. The Columbus module is out that way about eight feet or so and the station crew and Hans have been busy all morning opening it up, activating it, getting it going."

Asked if Columbus had "that new car smell," Schlegel said it "definitely has it."

"It's just a huge volume that we have now," he said. "We couldn't be happier. But of course, you don't forget, we still have a lot of activation to go."

Because of medical privacy concerns, NASA managers provided no details earlier in the mission when Schlegel became ill. The mission's first spacewalk was delayed one day, from Sunday to Monday, and Schlegel was replaced by astronaut Stan Love. It was the first time a U.S. spacewalk had been delayed by a medical issue since the fifth shuttle mission in 1982.

Today's interview was the first chance reporters had to ask Schlegel about what happened. Frick, however, answered the first medical question, saying "every space flight is different and a lot of times crew members haveÊtemporary conditions that are an issue for a little while and they clear right up."

"We were just really happy we always have backups trained," he said. "You know, Alan Poindexter here is trained on all my tasks so if anything happens to me he can do everything I'm trained to do. And all the EVA crew members have trained to do everyone else's tasks. So it all worked out and we were able to get EVA-1 off and get all our major tasks done. Hans will be going out tomorrow on EVA-2 to get our next most important task done as we work through our mission."

Asked for a direct response about how he felt, Schlegel said: "I feel really great right now. I'm, of course, a little bit anxious because tomorrow will be my first EVA. I fully respect the decision (to put Love on the first spacewalk) to make the most success out of our mission so far. Nobody could have been happier than me when we finished EVA-1 with the major objectives all done. That's all I want to say because medical issues are private."

Asked how disappointed he was to miss a spacewalk after years of training, Schlegel said "that must be your point of view, but I've been training as a mission specialist since 10 years and I worked several missions as a CAPCOM (spacecraft communicator) and a lead CAPCOM. And the major thing is our big mission. And it's not NASA's mission, it's a mission of the international community and no matter who does the job, main thing is it has to be done and done in the right way and I think we, the two crew members outside and here inside and the ground teams, did an excellent job during EVA-1. And of course, personally, I don't, how do you say it, I don't deny it's a little bit bitter when that decision is the best decision, but that's only personal. The bigger scheme is what's important."

The shuttle-station astronauts spent the day opening up and activating Columbus. Alan Thirkettle, the space station program manager with the European Space Agency, said engineers encountered a few minor hiccups, including a computer that did not initially synchronize with a backup and a water pump in the cooling system that indicated possible problems. NASA flight controllers, meanwhile, ran into problems of their own getting the new module hooked into the station's primary cooling system.

But Thirkettle characterized the problems as typical of what could be expected when activating complex systems for the first time.

"We can echo the happiness everyone else has alluded to," Thirkettle said. "We are very pleased indeed to see crew finally inside the laboratory. They're doing the first thing that the crew does, which is to make a complete mess of what was a beautiful piece of clean hardware inside! But that's to get access to all the things that are going to be useful for the module."

Schlegel said Columbus represents "the beginning of manned space flight for Europe."

"We have all the sudden the opportunity to do experiments around the clock, throughout the year, we have a control center in Germany, a European control center close to Munich, which is operating around the clock to do many experiments and control the systems of Columbus," he said. "And even more, you know, we have also gained obligations. From now on, we have to participate in the costs and the operation of the international space station. And (next month), we'll launch (the first) ATV, the automated transfer vehicle, from a European Ariane 5 and that clearly marks that Europe is as engaged in human space flight as it has never been before. We are looking forward to it."

Schlegel and astronaut Rex Walheim are spending the night in the space station's Quest airlock module at a reduced pressure of 10.2 psi, part of a so-called camp-out procedure to help flush nitrogen from their bodies to prevent the bends after a spacewalk in NASA's low-pressure suits.

If all goes well, they will float outside around 9:30 a.m. Wednesday for a six-and-a-half-hour spacewalk to replace a nitrogen tank used to pressurize the station's ammonia coolant lines. Thirkettle told reporters today NASA and the European Space Agency were in agreement about the original decision to replace Schlegel with Love for the first spacewalk and the decision to let the German astronaut proceed with the second.

"As far as I know, everybody's looking forward to Hans doing this," he said. "There's not an ESA-NASA conflict over this, there never has been and I very much doubt there ever will be. Hans is looking forward to this. ... I think we're all in synch on this."

11:14 AM, 2/12/08, Update: European astronauts begin Columbus activation

Newly arrived French astronaut Leopold Eyharts and German shuttle flier Hans Schlegel opened hatches and partially entered the European Space Agency's Columbus research module today, marking the moment with a call to flight controllers in Houston, Moscow and now, Oberpfaffenhofen near Munich, Germany.

"Houston, and Munich, Hans and I are both together here, ready to ingress the Columbus module," Eyharts radioed at 9:08 a.m. "We have a special thought at this moment for all the people in Europe and the U.S. who have contributed to the make up of Columbus. Especially to the space agencies, of course, the industry, but also all the citizens who are supporting space flight. This is a great moment and Hans and I are very proud to be here and to ingress for the first time the Columbus module."

Schlegel, looking comfortable and in good spirits after being ill earlier in the mission, added: "We are very proud. I think it starts a new era now, the volume of the European scientific module, Columbus, and the ISS are connected for many, many years of research in space in cooperation, internationally. It's a great moment for us."

After congratulations from mission control in Houston, the German control center came on the line to say "thanks a lot, Leo and Hans, for these very kind words. That's the great news we've been waiting for. Let me also take this chance to thank you all, ISS and shuttle crew members, and congratulate you for the fantastic job you did yesterday for the Columbus installation. So now bon chance and good luck to you."

The astronauts are busy today hooking up power lines, data cables and coolant loops to carefully bring the new science lab to life. The astronauts won't fully enter the module for normal work until this afternoon, after allowing time for fans and filters to clean the air in the lab.

While the activation work was proceeding, mission control in Houston told shuttle commander Steve Frick engineers had completed an analysis of a slightly pulled up insulation blanket on the ship's aft right orbital maneuvering system rocket pod.

"It's good news on the right OMS pod blanket," astronaut Keven Ford radioed from the control center. "They did the analysis that clearly shows there's no safety-of-flight issue. That's based on a very conservative modeling of that anomaly. So the right OMS area has been officially cleared for entry."

"OK, that's great news, Kevin," Frick replied. "Thanks a lot to the inspection folks and the analysis folks that did the thermal on that and cleared it for us. It's a relief knowing we don't have to go back there and mess with it."

"We agree, Steve. We've got plenty on our plate."

6:45 PM, 2/11/08, Update: Astronauts gear up for Columbus ingress, outfitting

Wearing a protective mask and safety goggles, European Space Agency astronaut Leopold Eyharts plans to enter the new Columbus science lab today, kicking off a busy month of activation and commissioning for the space station's newest module.

"There is a sight that everybody in Europe has been looking forward to for a very, very long time: Columbus now attached to the (station), ESA Program Manager Alan Thirkettle said Monday after the lab was successfully installed. "February the 11th was another great day for the European Space Agency, a great day for our European industry and a great day for Europe in general.

"The mechanical guys have done their bit," he said. Today, "we get the electricians and the plumbers in to hook it up ... and go through activation and go through ingress into the module. Leo will get himself nicely dressed up in his goggles and his mask and everything, but he'll go inside and see that the inside looks just as good as the outside of this thing.

"So now we have four of the international partners with their elements on the station," Thirkettle said. "It's really becoming the 'international' space station and we're very, very much looking forward to having the fifth partner (Japan) join us next month. ... It's really a nice partnership."

The bus-size Columbus module was attached to the right-side hatch of the forward Harmony connecting module (also known as Node 2). The station's robot arm remained attached to the new module overnight, providing power to internal heaters until the astronauts can plug in normal station power, along with data lines and ammonia coolant loops, later today.

The flight plan called for Eyharts to make a so-called partial ingress into the module around 8:50 a.m., although that could move earlier. The crew will officially enter the module to begin its outfitting around 2:55 p.m.

"Today's the big day where we're going to activate the Columbus module," station Flight Director Ron Spencer said early today. "Right now, it's just structurally attached to station. The crew actually started part of this last night before they went to bed. There's a small pressurized volume in between the Columbus hatch and the Node 2 hatch and so they did a leak check of that to make sure that area can hold pressure before they enter that area this morning.

"This morning what they're going to be doing is, first they're going to start by hooking up power jumpers, fluid lines, data lines to allow Columbus to receive power and other resources from space station," Spencer said. "Once that's done, they'll open up the hatch and go inside. ... The ground, once they get these power jumpers hooked up and the data lines and fluid lines to allow it to talk to station, the ground teams are going to start turning on systems inside Columbus, turning on the power boxes, computers, life support systems, et cetera. So it's a busy day for the station crew to get that going."

Station commander Peggy Whitson and Atlantis astronaut Hans Schlegel, a European Space Agency specialist in Columbus systems, will oversee connection of power, data and coolant lines.

"As soon as Peggy and Hans get the jumpers hooked up to allow Columbus to receive ground commands, then it's the Columbus flight controllers (near Munich, Germany) who are actually going to be turning on the systems and they'll have control of it from that moment," Spencer said.

Here is an updated timeline of today's activities (in EST and mission elapsed time; includes revision E of the NASA television schedule):

EST........DD...HH...MM...EVENT

02/12/08
04:45 AM...04...14...00...STS/ISS crew wakeup
06:15 AM...04...15...30...Flight director update on NASA TV
06:35 AM...04...15...50...ISS daily planning conference
07:45 AM...04...17...00...Logistics transfers
07:55 AM...04...17...10...Station robot arm (SSRMS) ungrapples Columbus module
08:45 AM...04...18...00...Power jumper installed
08:53 AM...04...18...05...PAO event (Frick, Melvin, Walheim, Love)
08:50 AM...04...18...05...Partial ingress into Columbus module
09:15 AM...04...18...30...Shuttle KU-band antenna redeploy
11:05 AM...04...20...20...Cooling system jumper installed
11:30 AM...04...20...45...Crew meals begin
01:00 PM...04...22...15...EVA-2: Airlock preps
01:45 PM...04...23...00...EVA-2: Tools prepped
02:55 PM...05...00...10...Columbus module ingress
03:30 PM...05...00...45...Mission status briefing on NASA TV
04:35 PM...05...01...50...PAO event (Frick, Poindexter, Schlegel)
04:55 PM...05...02...10...EVA-2: Procedures review
07:00 PM...05...04...15...EVA-2: Mask pre-breathe for campout
07:55 PM...05...05...10...EVA-2: Campout begins (10.2 psi depress)
08:15 PM...05...05...30...ISS crew sleep begins
08:45 PM...05...06...00...STS crew sleep begins
09:00 PM...05...06...15...Daily video highlights reel on NASA TV

"You build it in a clean environment and you take great steps to keep from generating foreign object debris," said Kirk Shireman, deputy space station program manager at the Johnson Space Center in Houston. "It can be something as simple as metal shavings when you're drilling a hole into a bracket. So we go through great efforts to keep that stuff as clean as we can. ... But when you build in a one-(gravity) environment, you can have FOD that falls down behind (something) and is not visible to you. When you get in zero G, it all floats up and floats around.

"And so we have the crew wear protective goggles and masks until we have a certain amount of air recycling," he said. "When we turn the fans on and recycle that air, all that debrisÊthat's floating around will make its way to filters in front of the fans. There's a certain number of times we turn over the atmosphere in the module and after that, the requirements to wear goggles and masks is relieved."

Once inside the new module, Eyharts and his crewmates will get busy with commissioning activities, re-arranging science racks in preparation for the start of normal science operations over the next few weeks.

"When everything is up and running we'll be able to ingress the module and do the first installation of equipment inside the module," Eyharts said in a NASA interview. "This is, of course, a very important part of our work because, for instance, the scientific racks (were) not be launched in their final position because of some issues with the center of gravity of the shuttle. So once the module is attached to the station we have to move a few of the scientific racks into their final location, and, in addition, install other equipment."

This afternoon, the astronauts will review plans for a spacewalk Wednesday to replace a spent nitrogen tank used to pressurize the station's ammonia coolant system. Rex Walheim and Schlegel are scheduled to spend the night in the station's Quest airlock module to help purge nitrogen from their bloodstreams before working in NASA's lower-pressure space suits.

Schlegel was replaced by astronaut Stan Love for the first spacewalk of the mission Monday due to a medical problem. Spencer said today Schlegel will participate in the second spacewalk as originally planned.

5:02 PM, 2/11/08, Update: Spacewalk ends

Astronauts Rex Walheim and Stan Love closed the outer hatch of the Quest airlock and began repressurizing the module at 5:11 p.m. to officially end an extended seven-hour 58-minute spacewalk. This was the 102nd spacewalk devoted to station assembly and maintenance since construction began in 1998, the third excursion for Walheim and the first for Love, who replaced German astronaut Hans Schlegel.

"Congratulations on an outstanding EVA 1," outgoing station astronaut Dan Tani radioed. "You guys did a great job."

5:00 PM, 2/11/08, Update: Columbus module attached to space station

The European Space Agency's Columbus laboratory module was successfully removed from the shuttle Atlantis' cargo bay today and bolted to its permanent home on the front right side of the international space station to accomplish the primary goal of the year's first shuttle mission. "Columbus is touching the station for the first time," French astronaut Leopold Eyharts radioed at 4:29 p.m. as the station's robot arm, operated by shuttle astronaut Leland Melvin, moved Columbus into position for bolting.

"All right!" someone exclaimed. "Good job, guys!"

A few minutes later, motorized bolts in the common berthing mechanism engaged to pull Columbus firmly into place on the right-side port of the Harmony connecting module.

"Houston and Munich, the European Columbus laboraory module is now part of the ISS," Eyharts radioed at 4:44 p.m.

"Beautiful work," astronaut Chris Cassidy called from mission control in Houston.

"We see a good A bolting and that finishes our CBM (common berthing mechanism) procedure," Eyharts concluded.

"We see the same on the ground, Leo," Cassidy agreed. "Nice job to all involved."

After leak checks and preparations inside Harmony, the astronauts plan to open hatches to the new module Tuesday to begin activating the laboratory and its complex systems.

Astroantus Rex Walheim and Stan Love, meanwhile, are in the final stages of stowing tethers and tools before repressurizing the Quest airlock module to end an extended spacewalk.

4:00 PM, 2/11/08, Update: Astronauts told to wrap up spacewalk

Running a bit behind schedule, astronauts Rex Walheim and Stan Love were told to defer a few minor tasks to a spacewalk Wednesday and to begin wrapping up a successful spacewalk while crewmate Leland Melvin, operating the space station's robot arm, continued moving the new Columbus module toward its home on the international lab complex.

Commander Steve Frick radioed congratulations to Walheim and Love, saying "man, you guys have done an amazing job. We're looking out our window here at Columbus about halfway there. I can't believe how much work you've gotten done on a tough EVA. This has just gone awesome. Can't wait to see you guys back inside."

Walheim and Love attached a grapple fixture to the Columbus module, hooked up electrical cables and removed protective covers over the lab's docking mechanism, clearing the way for Melvin to pull the bus-sized module out of the shuttle's cargo bay.

After recharging their spacesuit oxygen supplies in the Quest airlock module, the flight plan called for the spacewalkers to make preparations for replacing a nitrogen tank used to pressurize the station's ammonia coolant system. The actual swap out is planned for a second spacewalk Wednesday.

But because they were a bit behind schedule, flight controllers asked them to defer disconnecting electrical cables and two ammonia flex hoses. That work will be carried out later this week. Walheim did, however, press ahead with work to unfasten bolts on the tank assembly.

Love, making his first spacewalk, was asked to loiter at the airlock a few moments after recharging his oxygen supply, giving him a chance to marvel at the view.

"Columbus is on the move!" he exclaimed. "I was not expecting to be watching th e install from this perspective."

A few minutes later, he alerted flight controllers to what appeared to be a debris impact on an astronaut handrail around the Quest airlock module's outer hatch.

"Looks to me like a little impact crater," he said. "It is right where everybody grabs on the way out of the airlock."

In recent months, flight controllers have been concerned about unseen sharp edges on the station believed to be responsible for causing small tears in the protective covering on spacesuit gloves. Love was asked to take pictures of the damage, but it's not yet known whether the presumed crater he reported could be responsible for any such glove damage.

03:00 PM, 2/11/08, Update: Station arm pulls Columbus module from cargo bay

Astronaut Leland Melvin, a former college football star drafted by the Detroit Lions, used the international space station's robot arm today to carefully pull the European Space Agency's Columbus research module out of the shuttle Atlantis' cargo bay.

Working with careful deliberation, Melvin, assisted by outgoing station astronaut Dan Tani and his replacement, Leopold Eyharts, slowly inched the 28,200-pound module out of the cargo bay at 2:56 p.m. using a grapple fixture that was attached to the bus-size laboratory earlier today by spacewalkers Rex Walheim and Stan Love. It was the first step in a carefully choreographed sequence of maneuvers to move the module to the front of the station for attachment to the right side of the Harmony connecting module.

"Columbus has started its trip to the new world," Tani quipped as the Canadian-built robot arm slowly pulled the module free.

"All right," one of the spacewalkers replied.

The 22.5-foot-long Columbus will add some 2,600 cubic feet of volume to the station after it is pulled into place by motorized bolts. Built by EADS Space Transportation, Columbus was launched with four European science racks and one European storage rack in place. NASA later will install five racks of its own. The European Space Agency has spent about $2 billion building Columbus, the experiments that will fly in it and the ground control infrastructure necessary to operate them.

"The laboratory modules are why we're doing it," NASA Administrator Mike Griffin said last week. "On the space station, it's really two things. It's a place to learn how to live and work in space, which we need to do, and for a long period of time before we go to Mars. It's also a place to do the research we would like to do in a better way than we've been able to do it in the more confined places we've flown in before.

"So now, more than a fourth of our laboratory capacity on the station as a whole is going up on this flight. It puts the Europeans into human spaceflight in a visible and permanent way. As you say, it makes the station a truly international collaboration, just every thing about it is good."

While Melvin and Tani worked to move Columbus into place for attachment to Harmony, Walheim and Love took a moment to recharge their spacesuit oxygen supplies before moving up to the station's main solar power truss. They plan to up tools and make preparations to replace a nitrogen tank during a spacewalk Wednesday. The tank was used to pressurize the station's ammonia cooling system and a replacement was launched aboard Atlantis.

11:15 AM, 2/11/08, Update: Spacewalkers work to install robot arm fixture on Columbus module

Two hours into today's spacewalk, astronauts Rex Walheim and Stan Love have finished setting up tools and equipment and are preparing to install a grapple fixture on the side of the Columbus research module in Atlantis' cargo bay.

"Welcome to spacewalking, buddy," Walheim, veteran of two previous spacewalks, told Love, making his first, as the excursion began.

"Wow," Love marveled at the view of Southeast Asia 210 miles below.

"Pretty slick."

"It's awesome."

Love, anchored to the end of the space station's robot arm, released the grapple fixture from its mounting point on the side of the cargo bay and plans to bring it to the European lab module where Walheim is removing the first of two panels to permit the fixture's attachment.

The power and data grapple fixture, or PDGF, will be attached with four expandable fasteners. Once it's in place, a second debris shield will be removed so two electrical cables can be connected to provide power from the robot arm to heaters in the Columbus module. The heaters will keep systems in Columbus from getting too cold during the slow move up to the space station. Once bolted to the Harmony module, Columbus will be plugged into normal station power.

After the two debris shields are re-installed, the astronauts will remove eight covers protecting the common berthing mechanism hardware on Columbus that will help attach the module to the station. Love then will get off the robot arm and stow the foot restraint.

At that point, Walheim and Love will be done with Columbus preparations. After returning to the Quest airlock module to swap out tools, they will make their way up to the station's main solar power truss to set up tools and hardware needed for the planned changeout of a nitrogen tank during a second spacewalk Wednesday.

Robot arm operators Leland Melvin and Dan Tani, meanwhile, will press ahead with moving Columbus up to the Harmony module's right-side port so motorized bolts can pull the lab into place. That work is scheduled for late this afternoon.

While the astronauts were busy in orbit, engineers rolled the shuttle Endeavour from its processing hangar into the Vehicle Assembly Building at the Kennedy Space Center today for attachment to an external tank and two solid-fuel rocket boosters. If all goes well, Endeavour will be hauled to launch pad 39A next week. Liftoff on the next space station assembly mission is targeted for 2:28 a.m. on March 11.

09:20 AM, 2/11/08, Update: Spacewalk begins

Running about 15 minutes ahead of schedule, astronauts Rex Walheim and Stan Love switched their spacesuits to battery power at 9:13 a.m. to officially begin a planned six-and-a-half-hour spacewalk. The goal of the excursion is to prepare the European Columbus module for attachment to the international space station.

"We're going over Lake Geneva. And the Alps! Wow..." Walheim marveled looking at the Earth 210 miles below. "It's awesome!"

This is the 102nd spacewalk devoted to station assembly and maintenance since construction began in 1998, the third for Walheim and the first for Love, who is replacing German astronaut Hans Schlegel for today's excursion.

Here is a revised timeline for today's spacewalk based on the actual start time (in EST and event elapsed time):

EST........DD...HH...EVENT

09:13 AM...00...00...EVA-1: Spacesuits to battery power
09:18 AM...00...05...EVA-1: Airlock egress
09:33 AM...00...20...EVA-1: Power-Data Grapple Fixture setup
11:13 AM...02...00...EVA-1: PDGF installation on Columbus module
01:28 PM...04...15...Station robor arm (SSRMS) grapples Columbus
01:28 PM...04...15...Harmony vestibule outfittig preps
01:43 PM...04...30...EVA-1 (Walheim): Nitrogen tank removal prep
01:48 PM...04...35...SSRMS unberths Columbus
01:53 PM...04...40...EVA-1 (Love): Nitrogen tank removal prep
03:13 PM...06...00...EVA-1: Cleanup and airlock ingress
03:43 PM...06...30...Columbus attachment begins
03:43 PM...06...30...EVA-1: Airlock repressurization

6:30 AM, 2/11/08, Update: Walheim, Love suit up for Columbus install spacewalk

Astronauts Rex Walheim and Stan Love are suiting up this morning in preparation for a planned six-and-a-half-hour spacewalk to ready the European Space Agency's Columbus research module for attachment to the international space station. The excursion is scheduled to begin around 9:35 a.m. and if all goes well, astronauts Dan Tani and Leland Melvin, a former football star operating the space station's robot arm, will pull Columbus out of the shuttle Atlantis' cargo bay shortly after 2 p.m. and move it into place for robotic attachment to the lab complex.

The shuttle/station astronauts were awakened at 4:46 a.m. by a recording of "Fly Like and Eagle" beamed up from mission control in Houston.

"Good morning, Atlantis," astronaut Shannon Lucid called from the control center. "And a special good morning to you today, Leland."

"Good morning, Shannon," replied Leland, who became an astronaut after an injury ended his chance to play professional football. "And that was a great way to wake up today on a day we're going to install Columbus. I want to thank my family and especially my sister for believing in me so much, she let me know that I can fly like an Eagle, which we're doing overhead right now."

Walheim and Love will begin today's spacewalk from the station's Quest airlock module on the right side of the central Unity module. Love, originally scheduled for just one spacewalk - EVA-3 - replaced German astronaut Hans Schlegel for today's outing after Schlegel became ill earlier in the mission. While NASA will not discuss crew medical issues, Schlegel apparently is recovering and is expected to participate in a second spacewalk Wednesday as originally planned.

Walheim and Love spent the night in the Quest airlock at a reduced 10.2 psi pressure to help purge nitrogen from their bodies before donning their low-pressure spacesuits. Such "campouts" and additional procedures today are necessary to prevent the bends.

"We'll start out the way we start out all EVA days, which is, we get up, and we jump right into the timeline," commander Steve Frick said in a NASA interview. "The EVA folks, the ones that are going out that day in a spacesuits, have to get right into what we call the pre-breathe to get all the nitrogen out of their system. It takes a couple of hours. It's kind of a complicated procedure. We've got to make sure we do it exactly right so that they can go out the door safely.

"While they're just about ready to go out the door, the robotics team, Leland Melvin ... and also the station crew members that are robotics qualified - Dan Tani, Leo Eyharts, and (commander) Peggy (Whitson) - will be making sure that the space station's robotic arm is ready to grapple the Columbus module."

For identifical, Walheim (call sign EV-1) will wear a spacesuit with solid red stripes around the legs. Love (EV-2) will use a suit with broken red lines.

The first major objective of the spacewalk is to install a power and data grapple fixture - PDGF - on Columbus so the robot arm can lock on. The lab module could not be launched with the grapple fixture in place because that would make it "a little bit too big to fit into the payload bay," Walheim said.

"The grapple fixture is basically a big pin that the robot arm can grab onto and then pull the Columbus module out of the payload bay," he said in a NASA interview. "So we have to put that grapple fixture on there, and that's one of our main tasks, and then we have to get Columbus ready to be unberthed from the payload bay.

"One thing we have to do is remove some covers off the end of it where we're going to stick it onto the space station. We'll remove those covers, put them away, bring them back in, and also unplug its launch-to-activation cable, a cable that it has to give it power when it's in the payload bay. Then it'll be free to go and Leland and (Dan Tani) can grab it and pull it out of the payload bay and start attaching it to the space station."

Walheim also will inspect the common berthing mechanism on the Harmony module to look for any signs of debris that might prevent a tight seal when Columbus is bolted into place.

"We want him to make sure that the seal surface that the Columbus module's going to attach to ... is clear of any debris," station Flight Director Ron Spencer said early today. "We'd already scheduled this in the timeline and overnight, when we opened the (CBM) petals to prepare for this activity we may have observed a small piece of debris there. ... We're also going to have him go out with some Kapton tape in case there is debris there so he can remove that debris before we attach the Columbus module there, to make sure we have good seals to enable the pressurized environment once it's attached."

While Melvin and Tani maneuver Columbus into position for attachment to Harmony's starboard port, Walheim and Love will move up to the main solar array truss segment and begin preparations for replacing a nitrogen tank used to pressurize the station's ammonia coolant lines. A new tank carried up aboard Atlantis will be installed during a spacewalk Wednesday.

Inside the station, meanwhile, the astronauts will work to prepare the vestibule on the right side of the Harmony module for Columbus' eventual attachment.

"Once you have a module attached to the side of the space station you still have to make sure it's safe to open the hatches and get in there," said Frick. "You have to make sure the seals are tight, it's holding air, you have to disassemble a lot of equipment that's kind of blocking the path into the module, and once all that's done, basically, our day is over. So we're going to go to sleep that night and get up the next day, and then we're going to be able to go into the Columbus module."

Here is a timeline of major events Monday (in EST and mission elapsed time; includes revision D of the NASA TV schedule):

EST........DD...HH...MM...EVENT

02/11/08
04:45 AM...03...14...00...STS/ISS crew wakeup
05:20 AM...03...14...35...EVA-1: 14.7 psi airlock repress/hygiene break
06:15 AM...03...15...30...Flight director update on NASA TV
06:30 AM...03...15...45...EVA-1: Resume airlock preps
06:35 AM...03...15...50...ISS daily planning conference
08:00 AM...03...17...15...EVA-1: Spacesuit purge
08:15 AM...03...17...30...EVA-1: Spacesuit prebreathe
09:05 AM...03...18...20...EVA-1: Airlock depressurization
09:15 AM...03...18...30...Shuttle KU-band antenna stowed for Columbus unberthing
09:35 AM...03...18...50...EVA-1: Spacesuits to battery power (spacewalk begins)
09:40 AM...03...18...55...EVA-1: Airlock egress
09:55 AM...03...19...10...EVA-1: Power-data grapple fixture (PDGF) setup
11:35 AM...03...20...50...EVA-1: PDGF installation on Columbus module
01:50 PM...03...23...05...Station arm (SSRMS) grapples Columbus module
01:50 PM...03...23...05...Harmony prepared for Columbus attachment
02:05 PM...03...23...20...EVA-1: Walheim: nitrogen tank removal preps
02:10 PM...03...23...25...SSRMS unberths Columbus module
02:15 PM...03...23...30...EVA-1: Love: Nitrogen tank removal preps
03:35 PM...04...00...50...EVA-1: Payload bay cleanup and airlock ingress
04:05 PM...04...01...20...Columbus first stage bolting
04:05 PM...04...01...20...EVA-1: Airlock repressurization (spacewalk ends)
04:15 PM...04...01...30...Spacesuit servicing
04:25 PM...04...01...40...Columbus second stage bolting
04:40 PM...04...01...55...Columbus attachment to Harmony complete
05:00 PM...04...02...15...Centerline berthing camera removal
05:30 PM...04...02...45...Mission status/MMT briefing on NASA TV
08:15 PM...04...05...30...ISS crew sleep begins
08:45 PM...04...06...00...STS/ISS crew sleep begins
09:00 PM...04...06...15...Daily video highlights reel on NASA TV

5:01 PM, 2/10/08, Update: Schlegel expected to participate in Wednesday spacewalk

NASA managers expect European astronaut Hans Schlegel to participate in a spacewalk Wednesday, the second of three excursions planned by the shuttle Atlantis' crew. Schlegel, a 56-year-old father of seven, originally planned to join astronaut Rex Walheim for the crew's first spacewalk today. But the EVA was delayed 24 hours - and Schlegel was replaced by Stan Love - when the European Space Agency astronaut apparently became ill after launch last week.

NASA managers have refused to provide any details about the nature of the illness or even confirm who on the shuttle/station complex was sick. They would only say the illness was not life threatening and that no mission objectives were threatened by the spacewalk delay and crew shuffle. Today they would not directly say whether flight surgeons had cleared Schlegel for the second spacewalk.

But lead Flight Director Mike Sarafin said "the plan right now is to perform the rest of the mission as planned." That would mean he expects Schlegel to be available for the second spacewalk Wednesday.

Asked if the medical issue, whatever it was, had been resolved, Mission Management Team Chairman John Shannon would only say: "The flight surgeons, as they always do, they stay in contact with each of the crew members and they discuss their status and then they feed it back to us and it's an ongoing process. Right now, like MIke said, the plan is as the plan was pre-flight and that's the way we're going to go execute it. If they come back to us and say that's changed, then we'll react to that change."

Reporter: "So for the time being, the medical issue is resolved?"

Shannon: "There are no changes to the plan as it's currently laid out."

Schlegel looked relatively fit in television shots downlinked from space today as the astronauts worked through a hastily revised timeline, reviewing plans for Monday's spacewalk, transferring equipment to and from the space station and carrying out a detailed robotic inspection of a slightly pulled-up insulation blanket on the ship's right rear rocket pod.

The so-called focussed inspection was ordered after image analysts noticed a corner of the blanket had pulled up during Atlantis' climb to space Thursday. In close-up television views today, it appeared the stitching along the seam between two adjacent blankets had come apart, allowing a small, triangular section of one blanket corner to pull up slightly. The damage did not appear serious to the untrained eye, but Shannon said engineers have not yet reached a conclusion on whether anything needs to be done.

Overall, he said, Atlantis is in good condition with no signs of problems with the ship's critical underside heat shield, nose cap or wing leading edge panels, which experience the most extreme heating during re-entry.

"The thermal protection system inspections that we do are going extremely well," Shannon said. "It's the fastest I've ever seen them done on a flight. We have completely cleared the bottom of the orbiter, there are no issues we are working on the bottom, all of the reinforced carbon carbon on the wings and the nose are completely cleared. We're gathering additional information on the right OMS pod. There's really no change from (Saturday).

"There's also a couple of small tile chips around the crew windows on the front of the vehicle. Nobody expects them to be any issues at all, we just have not gotten to the point of analyzing them yet. I would expect by Tuesday we'll have all that work done and be able to completely clear the orbiter."

The astronauts were asked to change out a computer hard drive today in order to downlink photographs shot by a camera in the belly of the orbiter showing the ship's external tank after initial separation in orbit. Those pictures will be added to other views to help engineers assess the performance of the tank's foam insulation as NASA gears up to launch shuttle Endeavour on the next station assembly mission around March 11.

Shannon said both of Atlantis' spent booster rockets had been recovered and towed back to port. The right side rocket was at the booster processing facility Sunday and video shot during ascent, possibly showing when the rocket pod blanket peeled back, should be ready for review by early Monday. The ship towing the left-side booster has been held up by windy weather and its video is expected later in the week.

"Since the right OMS pod is where the blanket lifted up and we'd like to see when that happened, we were a little bit lucky and got the correct booster in first before the winds kicked up," Shannon said.

Otherwise, he concluded, "we're really looking forward to watching the crew and the ground ops team place Columbus in its final home and we're very excited about that tomorrow."

Walheim and Love plan to begin the mission's first spacewalk at 9:35 a.m. Monday. Their primary objective is to attach a robot arm attachment fitting to the European Columbus research module so Leland Melvin, operating the space station's robot arm, can pull it out of Atlantis' cargo bay. Walheim and Love will then make preparations for replacing a large nitrogen tank used for pressurizing the station's ammonia cooling system.

Melvin, meanwhile, will move Columbus into position for attachment to the right side hatch of the forward Harmony module so motorized bolts can engage to lock it in place. The astronauts plan to enter the module for the first time Tuesday. If all goes well, Walheim and Schlegel will stage a second spacewalk Wednesday with Walheim and Love carrying out a third and final excursion Friday.

Here is a timeline of major events Monday (in EST and mission elapsed time; includes revision C of the NASA TV schedule):

EST........DD...HH...MM...EVENT

02/11/08
04:45 AM...03...14...00...STS/ISS crew wakeup
05:20 AM...03...14...35...EVA-1: 14.7 psi airlock repress/hygiene break
06:15 AM...03...15...30...Flight director update on NASA TV
06:30 AM...03...15...45...EVA-1: Resume airlock preps
06:35 AM...03...15...50...ISS daily planning conference
08:00 AM...03...17...15...EVA-1: Spacesuit purge
08:15 AM...03...17...30...EVA-1: Spacesuit prebreathe
09:05 AM...03...18...20...EVA-1: Airlock depressurization
09:15 AM...03...18...30...Shuttle KU-band antenna stowed for Columbus unberthing
09:35 AM...03...18...50...EVA-1: Spacesuits to battery power
09:40 AM...03...18...55...EVA-1: Airlock egress
09:55 AM...03...19...10...EVA-1: Power-data grapple fixture (PDGF) setup
11:35 AM...03...20...50...EVA-1: PDGF installation on Columbus module
01:50 PM...03...23...05...Station arm (SSRMS) grapples Columbus module
01:50 PM...03...23...05...Harmony prepared for Columbus attachment
02:05 PM...03...23...20...EVA-1: Walheim: nitrogen tank removal preps
02:10 PM...03...23...25...SSRMS unberths Columbus module
02:15 PM...03...23...30...EVA-1: Love: Nitrogen tank removal preps
03:35 PM...04...00...50...EVA-1: Payload bay cleanup and airlock ingress
04:05 PM...04...01...20...Columbus first stage bolting
04:05 PM...04...01...20...EVA-1: Airlock repressurization (spacewalk ends)
04:15 PM...04...01...30...Spacesuit servicing
04:25 PM...04...01...40...Columbus second stage bolting
04:40 PM...04...01...55...Columbus attachment to Harmony complete
05:00 PM...04...02...15...Centerline berthing camera removal
06:00 PM...04...03...15...Mission status/MMT briefing on NASA TV
08:15 PM...04...05...30...ISS crew sleep begins
08:45 PM...04...06...00...STS/ISS crew sleep begins
09:00 PM...04...06...15...Daily video highlights reel on NASA TV

7:58 AM, 2/10/08, Update: Revised flight day 4 timeline

Here is the revised summary timeline for today, flight day 4, in EST and mission elapsed time:

EST........DD...HH...MM...EVENT

02/10/08
04:45 AM...02...14...00...STS/ISS crew wakeup
06:30 AM...02...15...45...ISS daily planning conference
07:00 AM...02...16...15...EVA-1: Procedures review (part 1)
09:00 AM...02...18...15...Eyharts Soyuz pressure suit leak check
09:45 AM...02...19...00...Logistics transfers
10:00 AM...02...19...15...Spacesuit swap
10:20 AM...02...19...35...EVA-1: Airlock preparations
11:00 AM...02...20...15...Shuttle crew joint meal
12:00 PM...02...21...15...Shuttle crew off duty
01:20 PM...02...22...35...Harmony vestibule outfitting preps for Columbus
02:15 PM...02...23...30...Focused inspection of protruding insulation blanket
03:00 PM...03...00...15...Mission status briefing on NTV
03:45 PM...03...01...00...EVA-1: Procedures review (part 2)
04:00 PM...03...02...00...Post-MMT briefing on NTV
04:45 PM...03...02...00...External tank umbilical camera downlink
05:25 PM...03...02...40...Wing leading edge, nose cap laser scan downlink
07:00 PM...03...04...15...EVA-1: Airlock campout
08:15 PM...03...05...30...ISS crew sleep begins
08:45 PM...03...06...00...STS crew sleep begins
09:00 PM...03...06...15...Daily video highlights reel on NTV

7:15 AM, 2/10/08, Update: Flight plan revised; equipment transfers, blanket inspection on tap

The Atlantis astronauts geared up for a hastily replanned day in space today, putting off their first spacewalk one day and instead focusing on equipment transfers to and from the space station and a robotic inspection of a protruding insulation blanket on one of the orbiter's aft rocket pods.

The spacewalk to prepare the European Space Agency's Columbus research module for attachment to the station was deferred one day because of an undisclosed medical problem with German astronaut Hans Schlegel. Schlegel trained to perform the first two of the mission's three spacewalks with astronaut Rex Walheim. Instead, he will be replaced on the first excursion by Stan Love, who already planned to join Walheim for the third EVA.

It is not yet known whether Schlegel will be allowed to carry out the second spacewalk, now set for Wednesday.

"Please forward to Hans all our best wishes," European mission control radioed today. "We're all keeping our fingers crossed for him to get better soon."

"Yes, Peter, I will do that for sure," newly arrived French astronaut Leopold Eyharts replied from the space station.

Other than saying the illness was not life threatening, NASA managers, citing medical privacy concerns, refused to provide any details about the nature or severity of the problem or even say which astronaut was involved. But when the astronauts were awakened today shortly after 4:45 a.m. by a German song beamed up for Schlegel from mission control in Houston, the 57-year-old father of seven sounded fit and in good spirits.

"Good morning, Atlantis," astronaut Shannon Lucid called from Houston. "And a special good morning to you today, Hans."

"Good morning, Shannon. Good morning, everybody," Schlegel replied. "Thank you very much for this piece of music. It's a German song about the nature of man, it was selected by my dear wife, Heike. Greetings to everybody in America, in Europe and in Germany and especially, of course, to my close family and my lovely wife, Heike. Thank you very much, Shannon."

Commander Steve Frick chimed in later, saying "we're looking forward to a little different day than we expected, but it'll be a good day on orbit, it looks like."

"Copy that. We will have some more words for the day in a few minutes," said astronaut Kevin Ford in Houston. "Great job on the rendezvous yesterday. It was spectacular."

"We appreciate you guys getting us there," Frick said. "Boy, station's an amazing view, I'll tell you. It's not much like the sims, at least the view, but the vehicle flies beautifully and the training that ... the guys gave us really worked out well. It went very easily."

There are at least two prior cases of crew illness interfering with a U.S. spacewalk. During Apollo 9, a shakedown flight for NASA's lunar lander, Rusty Schweickart became ill in orbit, forcing a one-day delay for a planned spacewalk. An EVA planned for the fifth shuttle mission was delayed one day when astronaut Bill Lenoir became ill. The spacewalk ultimately was called off because of spacesuit problems.

NASA has not yet finished revising the Atlantis crew's flight plan but the daily mission briefings will take place around the same times as originally planned. Here is revision B of the NASA television schedule (in mission elapsed time, EST and GMT):

ORB.EVENT.....................................DD/HH:MM...EST........GMT

SUNDAY, FEBRUARY 10 - FD 4
42...ATLANTIS/ISS CREW WAKE UP (FD 4).........02/14:00...04:45 AM...09:45
43...ISS FLIGHT DIRECTOR UPDATE...............02/15:45...06:30 AM...11:30
49.*.MISSION STATUS BRIEFING..................03/00:15...03:00 PM...20:00
50.*.POST-MMT BRIEFING........................03/01:15...04:00 PM...21:00
51.*.WALHEIM AND LOVE CAMPOUT BEGINS..........03/04:15...07:00 PM...00:00
52...ISS CREW SLEEP BEGINS....................03/05:30...08:15 PM...01:15
52...ATLANTIS CREW SLEEP BEGINS...............03/06:00...08:45 PM...01:45
53...FLIGHT DAY 4 HIGHLIGHTS..................03/06:15...09:00 PM...02:00 

"So, one of the main things we've scheduled for the crew to do today instead of the EVA is to go ahead and do a lot of that transfer of equipment from the shuttle over to the station and vice versa. Also on this mission, we're having a crew exchange (with Eyharts replacing Dan Tani) and so there's a lot of time we dedicate throughout the mission for the crew to do handover between the departing crew member and the arriving crew member so that they know where things are stowed, how things really work ... and pretty much a familiarization with their new home. So we've scheduled a lot of time for that today as well. And this will help us as the mission goes on to free up time once Columbus is installed, to devote most of the crew time toward Columbus."

Spencer said four hours has been blocked out for Love to review the plan for Monday's spacewalk. He and Walheim will spend the night in the space station's airlock at reduced pressure to help purge nitrogen from their bloodstreams before working in NASA's low-pressure spacesuits.

"We've given him four hours of time to study the EVA timeline since he was not originally scheduled to do this EVA," Spencer said. "He is familiar with the station ... so this won't be completely new to him. But since he wasn't trained for this specific task, we've given him four hours of time to study the plan and have HansÊavailable for question and answer, as well as the other crew members who were going to be involved with the EVA."

Later today, the astronauts will use cameras on a robot arm to inspect the shuttle's aft right orbital maneuvering system rocket pod where image analysts spotted a corner of one insulation blanket that has pulled up slightly along a seam.

NASA normally sets time aside on the fifth day of a shuttle mission to carry out a so-called focused inspection, but given the spacewalk delay, the work was added to today's schedule. The protruding blanket does not appear to be a serious issue, but "we don't know if the blanket's torn or if it's just protruding right there," Spencer said. "So we've dedicated some time to take more detailed images of that."

5:20 PM, 2/9/08, Update: Spacewalk delayed 24 hours by crew medical issue; Schlegel to be replaced by Love on first spacewalk; Shannon confirms mission extension, refuses to discuss reasons for delay

In a surprise announcement, flight controllers told the shuttle-station astronauts shortly after Atlantis docked with the lab complex to delay a planned Sunday spacewalk - and installation of the new Columbus research module - by 24 hours, extending Atlantis' mission by one day because of a crew medical issue.

German astronaut Hans Schlegel, originally scheduled to join Rex Walheim for the first two of three spacewalks planned for the mission, will be replaced by astronaut Stan Love when the module is attached on Monday. No reason was given for the delay and astronaut swap, but the shuttle crew requested two private medical conferences with flight surgeons earlier today.

NASA does not discuss astronaut health issues, citing concern about medical privacy issues, and John Shannon, chairman of NASA's Mission Management Team, refused to provide any details at an afternoon briefing.

"It's not life threatening," Shannon said, refusing to identify which astronaut was involved.

The shuttle docked with the space station at 12:17 p.m. but because of technical issues, only a few minutes of live video were downlinked. Late today, the astronauts replayed videotape showing the shuttle crew entering the station and Schlegel did not show any clear signs of discomfort.

"There was a medical issue with the crew," Shannon said during his briefing. "The flight surgeons - of course, we have flight surgeons who are closely involved with the crew at all times, they do private medical conferences with the crew throughout the mission - the crew called down and asked for one during the rendezvous, which was a little bit of a surprise to us. They talked to the crew members, they understood what the issue was. I will just say it is not going to impact any of the objectives of this mission."

But it will have a mission impact. The first of the three spacewalks planned for Atlantis' mission, originally scheduled for Sunday by Walheim and Schlegel, was devoted to helping attach the European Space Agency's Columbus research lab to the station. That work now will be delayed one day and Love, who is not believed to have trained as extensively for the work as Schlegel, will assist Walheim.

Citing medical privacy concerns, Shannon repeatedly refused to answer any questions about the nature of the medical issue, including whether the astronauts face any sort of contagious threat or whether Schlegel might be available for the second spacewalk of the mission, now targeted for Wednesday.

"You guys can fish all day, but I won't bite," Shannon said.

But about half the men and women who fly in space suffer nausea and other vestibular problems known collectively as space adaptation syndrome. But those symptoms typically go away by the second or third day of a mission as the astronaut becomes accustomed to the effects of weightlessness. Whether Schlegel, a 57-year-old German and father of seven making his second shuttle flight, was suffering from SAS was not known.

There are at least two prior cases of crew illness interfering with a U.S. spacewalk. During Apollo 9, a shakedown flight for NASA's lunar lander, Rusty Schweickart became ill in orbit, forcing a one-day delay for a planned spacewalk. An EVA planned for the fifth shuttle mission was delayed one day by crew illness and later called off because of suit problems.

Shannon said astronaut Leland Melvin, making his first flight, is the designated crew medical officer on board Atlantis and as such is "experienced in a variety of medical procedures. We carry a kit on board that has several different types of medicines and different medical capabilities and the crew is in constant contact with the flight surgeons on the ground. The flight surgeons know all about each crew members' medical history. It's something that's very well prepared for."

Shannon said Atlantis has plenty of supplies to support the one-day mission extension and, with additional power downs ordered late today, probably enough for a second day. NASA went into the flight planning to extend it by one day anyway to give the astronauts more time to activate the Columbus module.

The undisclosed medical issue "will cause us to re-arrange a few activities," Shannon said. "I think you heard it called up to the crew a little bit earlier that we're going to delay EVA number one by one day and it will be executed on flight day five. They also called up that Stan Love will replace Hans Schlegel as an EVA crew member.

"Stan has practiced all the activities of EVA-1 extensively and we talked it over with the crew and they're very happy with that and that's how we're going to go execute it," Shannon said. "So no impacts to the mission objectives, we just need to re-arrange some of the crew activities and when they happen. You might remember we went into this flight with one additional day we could add to it and we are very close to having a second day based on how we use the cryogenic consumables that produce electricity.

"We asked the team, since we are essentially going to use that one extension day tomorrow as a day for the team to prepare for EVA number one, we asked the team to power down the orbiter just a little bit more than they had planned pre flight to make sure we can get that second additional extension day. We have not decided to add that, but we're preserving the option to add it later on. If we don't add it, then that will just be more oxygen we can transfer over to the international space station."

Otherwise, Shannon said Atlantis is in good condition and that so far, no major problems have emerged during analysis of ascent and on-orbit photography of the shuttle's protective heat shield.

A small corner of one insulation blanket midway back on the shuttle's right side orbital maneuvering system rocket pod is pulled up and under study, but Shannon said it did not appear to be a serious problem

"Nobody is very excited about this one," he said. "It is in a much different position (than a blanket that was repaired on Atlantis' last flight). ... This is really shadowed by the pod, it's also shadowed by the wing. It does not see a very significant thermal environment. I don't expect this to be an issue but the team will continue to work it."

The only other issue of any significance involves one of Atlantis' flight computers, general purpose computer No. 3. GPC-3 failed to properly transition from "standby" to "run" when the astronauts powered up the full redundant set as part of their normal rendezvous procedures earlier today. Engineers believe the computer is healthy, Shannon said, but troubleshooting was deferred until after docking.

Shannon said engineers plan to read out the computer's memory to verify no hardware problems exist and then they will re-load flight software and in all likelihood, "it'll be just as good as new."

Flight planners are in the process of developing an alternate flight plan for Sunday. A revised NASA television schedule will be posted as soon as it becomes available.

03:45 PM, 2/9/08, Update: Engineers assessing pulled-up insulation blanket; computer issue

Engineers are assessing what, if anything, might need to be done about a small section of an insulation blanket on the shuttle Atlantis' right side orbital maneuvering system rocket pod that apparently pulled away from a seam during launch. Close-up photography of the rocket pod shows one corner of the blanket pulled up slightly, similar to a problem that cropped up on Atlantis during an August mission.

Lead Flight Director Mike Sarafin described the pulled-up corner as a "small tear" along a seam between adjacent blankets, adding "it's probably not that big of an issue, but we're off looking at it."

The insulation blankets on the OMS pods experience temperatures between 700 and 1,000 degrees Fahrenheit during the 15 minutes or so of peak heating during re-entry. Sarafin said he did not yet know the dimensions of the blanket corner in question, but the protruding triangular area spotted on the right-side rocket pod during Atlantis' August flight measured 4 inches by 6 inches.

In that case, a spacewalking astronaut pushed the flap back into place and secured it with surgical staples. Three spacewalks are planned during Atlantis' current mission and the same staple gun is on board if needed. But engineers have not yet determined what, if anything, needs to be done.

"We have some work to figure out if we need to gather some additional inspection imagery on that," Sarafin sad.

The only other technical issue of any significance is troubleshooting to verify the health of general purpose computer No. 3, one of five machines that control all aspects of shuttle operation.

GPC-3 failed to properly transition from "standby" to "run" when the astronauts powered up the full redundant set as part of their normal rendezvous procedures. Engineers believe the computer is healthy, Sarafin sad, but troubleshooting was deferred until after docking.

The incident occurred "when we brought it up out of a powered-down config earlier today," Sarafin said. "It had what we call a common set fail. Basically, when you bring up the multiple computers they all start talking to each other and that computer started talking to the other computers to make sure it was in synchronization and then it stopped for some reason. We're off investigating that."

The shuttle is equipped with four GPCs that run identical software and a fifth, backup computer that runs software from a different vendor to protect against the possibility of a bug or other problem that could disable the redundant set. At one point, NASA carried a spare GPC on board. While that is no longer the case, Sarafin said the failure of a single GPC would have no major impact on the mission.

12:25 PM, 2/9/08, Update: Shuttle Atlantis docks with space station

Wrapping up a textbook rendezvous, commander Steve Frick guided the shuttle Atlantis to a smooth docking with the international space station today after a spectacular slow-motion back flip directly below the outpost to let the lab crew photograph the ship's heat shield tiles. The linkup occurred at 12:17 p.m. as the two spacecraft sailed 209 miles above southern Australia at 5 miles per second. The station crew promptly rang the ship's bell, announcing the shuttle's arrival in accordance with naval tradition.

"Houston, Alpha/Atlantis. We have capture confirmed," station flight engineer Dan Tani radioed.

"Great indicator," commander Peggy Whitson agreed.

Today's docking was the first since the new Harmony connecting module was attached to the forward end of the U.S. Destiny laboratory late last year. The shuttle's docking port, pressurized mating adapter No. 2, was removed from Destiny and attached to the front end of Harmony in November to complete a major reconfiguration of the station's front end.

Atlantis' arrival, bringing the European Space Agency's Columbus research module and a new station crew member - French astronaut Leopold Eyharts - was a welcome birthday present for Whitson, who turned 48 today. A large "Happy Birthday" sign was stretched across the interior of the Destiny module to mark the occasion.

Atlantis also was a welcome sight for Tani, who was launched to the station last October and who's stay aloft was extended two months because of problems getting the shuttle off the ground in December.

Eyharts will officially replace Tani early Sunday, after his Soyuz seat liner and pressure suit are transferred to the station and it's Russian descent vehicle. Eyharts will remain aboard the station until late March when his ride home, the shuttle Endeavour, arrives carrying the first of two Japanese modules.

Whitson, Tani and Russian flight engineer Yuri Malenchenko planned to welcome their shuttle colleagues aboard with a brief ceremony in the Harmony module. After a safety briefing, the astronauts will get back to work, using the station's robot arm to pull the shuttle's heat shield inspection boom from its stowage location along the right side of the cargo bay.

The boom must be removed to clear the way for the unberthing of the Columbus module Sunday. The shuttle's robot arm can't reach it when the ship is docked to the station and once it's clear of the cargo bay, the station arm will hand the boom off to the shuttle's arm.

During the shuttle's approach to the station today, Whitson and Malenchenko photographed the belly of the orbiter as Frick guided the spaceplane through a dramatic end-over-end back flip as the two spacecraft passed high above the Atlantic Ocean. The station astronauts also photographed the shuttle's upper surfaces, paying special attention to Atlantis' right aft orbital maneuvering system rocket pod.

Engineers suspect one of the insulation blankets on the pod might have pulled up a bit during launch, but nothing obvious could be seen in close-up television views from the station. The higher-resolution digital still images should give engineers the views they need to assess the condition of the pad blankets as well as the critical heat shield tiles on the ship's belly.

Earlier today, the shuttle crew requested a private medical conference, or PMC, a somewhat unusual request in the midst of a rendezvous. A followup PMC was asked for shortly after docking but NASA does not discuss medical issues because of privacy concerns and it was not known what might have prompted the brief conferences.

10:00 AM, 2/9/08, Update: Shuttle crew begins terminal phase of space station rendezvous

The Atlantis astronauts fired the shuttle's maneuvering rockets today at 9:37 a.m. to begin the final phase of today's rendezvous with the international space station.

The space station will be in a so-called "biased" attitude, or orientation, today during docking to improve solar power generation. This is due to the cuYep.rrent beta angle, i.e., the angle between the sun and the plane of the station's orbit, and it's not the normal docking attitude familiar to commander Steve Frick from previous training. But he can perform a procedure known as a fly-out if any misalignment develops and flight controllers do not anticipate any problems.

The station's attitude will prevent normal Ku-band television downlink of the docking and may interfere with live TV of the traditional "welcome aboard" ceremony. If so, videotape is expected to be downlinked later.

Early today, one of the shuttle's four flight computers - GPC-3 - failed to properly transition from "standby" to "run" when the astronauts powered up the full redundant set. Engineers believe the computer is healthy, but they deferred troubleshooting until after docking.

In one other departure from normal operations, Frick was asked to loiter a bit when the shuttle reaches a point directly below the station to give the lab crew extra time to photograph insulation blankets on the orbiter's aft right-side rocket pod. A blanket may have pulled up a bit and the photography will help engineers assess its condition.

Docking is targeted for around 12:25 p.m., although that could slip a bit depending how long it takes to complete the blanket photography and the normal rendezvous pitch maneuver used to collect imagery of the shuttle's heat shield tiles.

06:10 AM, 2/9/08, Update: Astronauts gear up for rendezvous and docking

The Atlantis astronauts, closing in on the international space station, are gearing up for docking today to wrap up a two-day orbital chase. Looping below the lab complex and then up to a point directly in front of the station, commander Steve Frick plans to manually guide Atlantis to a linkup around 12:25 p.m.

Frick, pilot Alan Poindexter, flight engineer Rex Walheim, Leland Melvin, Stan Love and European Space Agency astronauts Hans Schlegel and Leopold Eyharts were awakened at 4:45 a.m. today by a recording of Garrison Keillor singing an ad for powdermilk biscuits from "A Prairie Home Companion."

"Good morning Atlantis," astronaut Shannon Lucid radioed from mission control. "And an especially great good morning to you today, Steve. It's a great day for rendezvous."

"Hey, thanks very much, Shannon," Frick replied. "Thanks very much to my wonderful wife, Jennifer, for a little powdermilk biscuits to wake up to in the morning. Our food's really healthy here on orbit, but we can still dream of some of the brown stains on the bag that indicate freshness."

The terminal phase of the rendezvous will begin at 9:37 a.m. with a rocket firing as the shuttle trails the station by about 9.2 miles. Approaching from behind and below, Frick will guide the orbiter a point about 600 feet directly under the space station a few minutes past 11 a.m. At that point, he will fire thrusters to pitch the shuttle around in a slow back flip known as a rotational, or rendezvous, pitch maneuver, or RPM.

As the shuttle's belly rotates into view, the station astronauts will use powerful telephoto lenses to capture high-resolution digital pictures of Atlantis' heat shield tiles. They also will photograph insulation blankets on the upper surfaces of the orbiter to help analysts on the ground assess the overall health of the shuttle's thermal protection system.

"The rendezvous pitch maneuver certainly is something that we like because it gives us a chance to get detailed photography of the entire shuttle to see the condition of the thermal protection system and really all the surfaces," Frick said in a NASA interview. "We're really excited that NASA was able to come up with such an interesting way to get a free inspection, basically.

"The maneuver from the shuttle side is very similar to the way it was when Eileen Collins' crew did it the first time. We pull up in our normal rendezvous profile, up underneath the space station about 600 feet away, and we just do a 360-degree flip, stop it when we're done, and then proceed with the rest of the rendezvous. For the space station crew, though, they're working harder and harder every time we do this. The first time we did it we just took photographs of the tile underneath the orbiter, and then we realized that the photography they took was so good and so accurate and detailed that, hey, there are other areas in the shuttle we could take a look at for free. So now they photograph the nose, the top of the orbiter, they photograph the engines on the back, the OMS [Orbital Maneuvering System] pods. So we basically map virtually the whole orbiter during that 360 degree flip maneuver.

"For us, we just do the flip and we proceed on into rendezvous and dock," Frick said. "The space station crew works real hard for that just couple of minutes when we're doing the flip, taking the photography, and then they get it right in their computers and get it downlinked to the ground so the ground starts looking at it within, sometimes, 40 to 45 minutes of when we've done the maneuver. We have the easy partÑjust a couple minutes of work. The ground then has the hard part which is many hours of analyzing all that photography to look for the smallest defects."

While the station crew is busy photographing Atlantis, the shuttle astronauts will enjoy a unique view of the lab complex.

"The advantage for us is we get to see the station in a very different way than we ever did before," Frick said. "We're used to just bringing the payload bay of the orbiter up to the space station for the entire rendezvous, so we see it in the same place. We kick off this flip maneuver and we see the station rapidly move over the nose and then a, a couple minutes later rise over the tail almost like a sunrise. It's real interesting and we're hoping to get some, some video of that to, to show the folks on the ground, 'cause it really is a different view than we normally get."

When the RPM ends, Atlantis will once again be in a nose-forward, payload-bay-to-station orientation. Frick will then guide the orbiter in a slow loop up to a point roughly 300 feet in front of the lab with the shuttle's tail facing Earth and its open cargo bay facing the station's docking port.

Today's docking will be the first for the station since the Harmony connecting module was attached to the forward end of the U.S. Destiny laboratory last year. The shuttle's docking port, pressurized mating adapter No. 2, was removed from Destiny and attached to the front end of Harmony. Atlantis' payload, the European Columbus research module, will be attached to Harmony's right-side port on Sunday.

"Obviously, the station's a little bit longer so it looks a little different, and we'll be in a little different position when we finally dock because of the length of (Harmony)," Frick said. "You're just at the end of a longer ship now. It's a little bit different, there isn't quite as much wiring going to the PMA now so we don't have as much redundancy when we dock to take care of the things that have to happen automatically, but Peggy [Whitson] and her crew have trained in order to cover those actions if they don't happen automatically, and we also have the ability to do that. So we just have to watch a few more things, but other than that it's going to be very similar to the last time."

After the shuttle docks, leak checks will be carried out and hatches will be opened around 1:30 p.m. for a traditional "welcome aboard." After a safety briefing to familiarize the shuttle crew with emergency procedures on the station, the astronauts will get busy transferring equipment for Sunday's spacewalk.

The crew also will use the station's robot arm to pull the shuttle's heat shield inspection boom out of the payload bay and hand it off to Atlantis' robot arm. The boom will be used to provide additional television views of critical mission events as well as a focused heat shield inspection if necessary. More important, the boom must be moved out of the way before the Columbus module can be unberthed on Sunday.

"It's an interesting ballet we have to do," Frick said. "Certainly we want to fly the boom because we need to inspect the orbiter's thermal protection system, especially the RCC (reinforced carbon-carbon) on the leading edge of the wings and the nose, but when we carry a large payload like Columbus up it's a pretty tight fit in the payload bay. And when you add this large boom on one side of the orbiter for the entire flight, we have to have some way to get it out of the way to be able to pull the Columbus module out and move it into position.

"It turns out it just would not fit very well if we had that boom in place. So after we dock the first thing we have to do is pull the boom out to get it out of the way for the next day when we get Columbus out of the bay. But the funny thing is, we can't actually reach it with the orbiter arm once we dock, so the station arm has to come down and grab it in a different location, pull it off of the orbiter, move it out to the side, and then the shuttle robotic arm will come in and grab it and take the hand-off from the station arm and move it out of the way so we'll be all set for the next day's activities."

Repeating from Friday, here is an updated timeline of today's activities (in EST and mission elapsed time):

DATE/EDT...DD...HH...MM...EVENT

02/09/08
04:45 AM...01...14...00...STS/ISS crew wakeup
06:15 AM...01...15...30...Group B computer powerup
06:30 AM...01...15...45...Space station (ISS) daily planning conference
06:30 AM...01...15...45...Begin rendezvous timeline
08:06 AM...01...17...21...NC-4 rendezvous rocket firing
08:50 AM...01...18...05...Middeck prepped for docking
09:05 AM...01...18...20...Spacesuits removed from airlock
09:37 AM...01...18...52...Terminal initiation (TI) rocket firing
09:45 AM...01...19...00...Station in docking orientation
10:10 AM...01...19...25...U.S. solar arrays feathered
10:12 AM...01...19...27...Station in rendezvous mode
10:15 AM...01...19...30...Sunset
10:15 AM...01...19...30...Russian command module lights on
10:36 AM...01...19...51...Range: 10,000 feet
10:44 AM...01...19...59...Range: 5,000 feet
10:50 AM...01...20...05...Range: 3,000 feet
10:52 AM...01...20...07...Sunrise
10:54 AM...01...20...09...MC-4 rendezvous rocket firing
10:58 AM...01...20...13...Range: 1,500 feet
11:03 AM...01...20...18...Range: 1,000 feet
11:06 AM...01...20...21...Shuttle KU antenna to low power
11:07 AM...01...20...22...Shuttle directly below station
11:12 AM...01...20...27...Range: 600 feet
11:19 AM...01...20...34...Noon
11:23 AM...01...20...38...Start shuttle pitch-around photo survey maneuver
11:27 AM...01...20...42...RPM full photo window close
11:31 AM...01...20...46...End pitch maneuver
11:34 AM...01...20...49...Initiate pitch up maneuver to point ahead of station
11:35 AM...01...20...50...Russian solar arrays feathered
11:45 AM...01...21...00...Shuttle directly ahead of station
11:46 AM...01...21...01...Range: 300 feet
11:47 AM...01...21...02...Sunset
11:50 AM...01...21...05...Range: 250 feet
11:54 AM...01...21...09...Range: 200 feet
11:57 AM...01...21...12...Range: 170 feet
11:59 AM...01...21...14...Range: 150 feet
12:03 PM...01...21...18...Range: 100 feet
12:06 PM...01...21...21...Range: 75 feet
12:10 PM...01...21...25...Range: 50 feet
12:13 PM...01...21...28...Range: 30 feet; start stationkeeping
12:18 PM...01...21...33...End stationkeeping; push to dock
12:23 PM...01...21...38...Range: 10 feet
12:23 PM...01...21...38...Sunrise

12:24 PM...01...21...39...DOCKING

12:45 PM...01...22...00...Leak checks
01:10 PM...01...22...25...Group B computer power down
01:15 PM...01...22...30...Docking system prepped for ingress
01:35 PM...01...22...50...Hatch opening
01:35 PM...01...22...50...Post-rendezvous laptop reconfig
02:05 PM...01...23...20...Safety briefing
02:55 PM...02...00...10...Station arm (SSRMS) grapples shuttle inspection boom (OBSS)
03:00 PM...02...00...15...Mission status briefing on NTV
03:25 PM...02...00...40...SSRMS unberths OBSS
03:55 PM...02...01...10...Airlock preps
04:30 PM...02...01...45...Shuttle arm (SRMS) grapples OBSS
04:45 PM...02...02...00...SSRMS ungrapples OBSS
05:00 PM...02...02...15...Post-MMT briefing on NTV (may move earlier)
05:25 PM...02...02...40...Spacewalk No. 1 (EVA-1): Procedures review
07:00 PM...02...04...15...EVA-1: Mask pre-breathe for campout
07:55 PM...02...05...10...EVA-1: Campout begins (10.2 psi depress)
08:15 PM...02...05...30...Station crew sleep begins
08:45 PM...02...06...00...Shuttle crew sleep begin
09:00 PM...02...06...15...Daily video highlights reel

04:22 PM, 2/8/08, Update: No obvious debris damage; shuttle performance near flawless going into Saturday docking

The shuttle Atlantis came through its eight-and-a-half-minute climb to space Thursday in good shape with no obvious signs of impact damage to the ship's protective heat shield. John Shannon, chairman of NASA's Mission Management Team, said today the shuttle was operating near flawlessly and while it will take several more days to complete a detailed post-launch inspection and analysis, "it looks like we had an extremely clean launch."

The first reports on the performance of foam insulation on Atlantis' external fuel tank "showed absolutely nothing of interest," Shannon said. "The two small foam losses we saw at 70 seconds and 110 seconds, the experts tell us those were not of a mass that we'd be concerned about. In addition, they did not appear to hit the underside of the vehicle. So it's absolutely no concern, we're not event tracking those anymore.

"There was another small foam event at 440 seconds," he added. "It appeared it might have bounced off the bottom of the vehicle, but we are well out of the atmosphere (at that point). That's well past the time that would be of concern and it was not of a mass that would cause us any issues. So from an ascent standpoint, at least what we've seen so far from the ground cameras and the on-board cameras, it looks like we had an extremely clean launch and ascent."

The Atlantis astronauts spent the day carrying out a detailed inspection of the shuttle's reinforced carbon carbon nose cap and wing leading edge panels, which experience the most extreme heating during re-entry. Shannon said those data, along with close-up photographs of the shuttle belly that will be shot by the station crew during Atlantis' final approach Saturday, will be assessed to determine whether any additional inspections are needed. A meeting to make that decision is planned for Saturday night, but as of this writing no obvious areas of concern have been identified.

"It's so far, an extremely clean flight," Shannon repeated. "The team at Kennedy Space Center that put the vehicle together should be really congratulated because it's performing flawlessly. I have never walked up into the engineering room that tracks every little problem that we have on the vehicle and seen a completely blank board. It is completely blank right now."

But Shannon said he cautioned Mission Management Team members to stay sharp because "we have a long way to go. ... But I absolutely could not have asked for a better start to it."

Lead flight director Mike Sarafin said the astronauts were on track for an on-time rendezvous and docking with the international space station Saturday. The terminal initiation burn, or TI rocket firing to kick off the final phase of the rendezvous, is scheduled for 9:37 a.m., setting up a docking at 12:25 p.m.

The goal of the mission is to attach the European Space Agency's Columbus research lab to the space station during a spacewalk Sunday. Along with inspecting the shuttle's wing lead edge panels today, the astronauts examined the spacesuits that will be used Sunday by Rex Walheim and Hans Schlegel; broke out hand-held lasers used during final approach and worked to complete setup of laptop computers that run critical rendezvous software.

"It's great to finally have Atlantis on orbit and the Columbus module on its way to the international space station," Sarafin said. "The mission is proceeding as we planned it. We haven't had any significant technical issues, the team is excited and definitely got their heads down and working hard to make the mission stay on that course.

"We're on track to dock to the international space station tomorrow. That'll be an opportunity to deliver a brand new module to Peggy Whitson, who's commanding the space station, on her 48th birthday."

Here is an updated timeline of Saturday's rendezvous and docking (in EST and mission elapsed time):

DATE/EDT...DD...HH...MM...EVENT

02/09/08
04:45 AM...01...14...00...STS/ISS crew wakeup
06:15 AM...01...15...30...Group B computer powerup
06:30 AM...01...15...45...Space station (ISS) daily planning conference
06:30 AM...01...15...45...Begin rendezvous timeline
08:06 AM...01...17...21...NC-4 rendezvous rocket firing
08:50 AM...01...18...05...Middeck prepped for docking
09:05 AM...01...18...20...Spacesuits removed from airlock
09:37 AM...01...18...52...Terminal initiation (TI) rocket firing
09:45 AM...01...19...00...Station in docking orientation
10:10 AM...01...19...25...U.S. solar arrays feathered
10:12 AM...01...19...27...Station in rendezvous mode
10:15 AM...01...19...30...Sunset
10:15 AM...01...19...30...Russian command module lights on
10:36 AM...01...19...51...Range: 10,000 feet
10:44 AM...01...19...59...Range: 5,000 feet
10:50 AM...01...20...05...Range: 3,000 feet
10:52 AM...01...20...07...Sunrise
10:54 AM...01...20...09...MC-4 rendezvous rocket firing
10:58 AM...01...20...13...Range: 1,500 feet
11:03 AM...01...20...18...Range: 1,000 feet
11:06 AM...01...20...21...Shuttle KU antenna to low power
11:07 AM...01...20...22...Shuttle directly below station
11:12 AM...01...20...27...Range: 600 feet
11:19 AM...01...20...34...Noon
11:23 AM...01...20...38...Start shuttle pitch-around photo survey maneuver
11:27 AM...01...20...42...RPM full photo window close
11:31 AM...01...20...46...End pitch maneuver
11:34 AM...01...20...49...Initiate pitch up maneuver to point ahead of station
11:35 AM...01...20...50...Russian solar arrays feathered
11:45 AM...01...21...00...Shuttle directly ahead of station
11:46 AM...01...21...01...Range: 300 feet
11:47 AM...01...21...02...Sunset
11:50 AM...01...21...05...Range: 250 feet
11:54 AM...01...21...09...Range: 200 feet
11:57 AM...01...21...12...Range: 170 feet
11:59 AM...01...21...14...Range: 150 feet
12:03 PM...01...21...18...Range: 100 feet
12:06 PM...01...21...21...Range: 75 feet
12:10 PM...01...21...25...Range: 50 feet
12:13 PM...01...21...28...Range: 30 feet; start stationkeeping
12:18 PM...01...21...33...End stationkeeping; push to dock
12:23 PM...01...21...38...Range: 10 feet
12:23 PM...01...21...38...Sunrise
12:24 PM...01...21...39...DOCKING
12:45 PM...01...22...00...Leak checks
01:10 PM...01...22...25...Group B computer power down
01:15 PM...01...22...30...Docking system prepped for ingress
01:35 PM...01...22...50...Hatch opening
01:35 PM...01...22...50...Post-rendezvous laptop reconfig
02:05 PM...01...23...20...Safety briefing
02:55 PM...02...00...10...Station arm (SSRMS) grapples shuttle inspection boom (OBSS)
03:00 PM...02...00...15...Mission status briefing on NTV
03:25 PM...02...00...40...SSRMS unberths OBSS
03:55 PM...02...01...10...Airlock preps
04:30 PM...02...01...45...Shuttle arm (SRMS) grapples OBSS
04:45 PM...02...02...00...SSRMS ungrapples OBSS
05:00 PM...02...02...15...Post-MMT briefing on NTV (may move earlier)
05:25 PM...02...02...40...Spacewalk No. 1 (EVA-1): Procedures review
07:00 PM...02...04...15...EVA-1: Mask pre-breathe for campout
07:55 PM...02...05...10...EVA-1: Campout begins (10.2 psi depress)
08:15 PM...02...05...30...Station crew sleep begins
08:45 PM...02...06...00...Shuttle crew sleep begin
09:00 PM...02...06...15...Daily video highlights reel

12:30 PM, 2/8/08, Update: Astronauts inspect heat shield

The Atlantis astronauts spent the morning scrutinizing the shuttle's nose cap and wing leading edge panels in a now-standard post-Columbia inspection carried out the day after launch to look for any signs of ascent debris impact damage. The crew also broke out equipment and began readying the orbiter for docking with the international space station Saturday.

Space station commander Peggy Whitson, who celebrates her 48th birthday Saturday, told CBS News today she's looking forward to Atlantis' arrival and delivery of the European Space Agency's Columbus research module.

"My present is a new module that we're going to install on the station," she joked. "I'm really looking forward to it."

The shuttle heat shield inspection was conducted using a 50-foot extension on the end of Atlantis' robot arm that is equipped with laser scanners and high-resolution cameras. Maneuvering the OBSS back and forth along the wing leading edge panels, the astronauts collected data that will be analyzed by engineers on the ground as the flight progresses.

"The first few times that we have done (this) inspection it took much longer to do, so our robotics, flight controllers and procedure developers have trimmed off quite a bit of time to make this a much faster process for inspection on flight day two," astronaut Leland Melvin said in a NASA interview. "You get faster by optimizing the trajectory of the motion of the arm, so instead of scanning down one side and then coming back and scanning another side, you might be able to get multiple scans in one motion. So thatÕs something that theyÕve done, looked at how to optimize the trajectory so that you donÕt have to make as many passes on the orbiter."

Melvin said it typically takes three crew members to carry out the inspection "so if someone gets a little tired or has to make a bathroom break or something we can all rotate out and get the job done."

Flight director Mike Sarafin will brief reporters on the progress of the mission at 3 p.m. A second briefing with Mission Management Team Chairman John Shannon is planned for 6 p.m., but may move earlier depending on how long it takes the team to complete its daily assessment.

Here is a timeline of today's activities (in EST) and mission elapsed time:

EST........DD...HH...MM...EVENT

02/08/08
04:45 AM...00...14...00...Crew wakeup
06:30 AM...00...15...45...Shuttle robot arm (SRMS) powerup
06:45 AM...00...16...00...SRMS checkout
07:35 AM...00...16...50...Laptop computer setup (part 2)
07:45 AM...00...17...00...NC-2 rendezvous rocket firing
08:10 AM...00...17...25...Orbiter boom sensor system (OBSS) unberth
08:35 AM...00...17...50...Ergometer setup
09:05 AM...00...18...20...Spacesuit checkout preps
09:10 AM...00...18...25...OBSS starboard wing survey
09:35 AM...00...18...50...Spacesuit checkout
11:05 AM...00...20...20...Spacesuits prepped for transfer to station
11:05 AM...00...20...20...OBSS nose cap survey
12:05 PM...00...21...20...Crew meal
01:05 PM...00...22...20...Spacewalk transfer preps
01:05 PM...00...22...20...OBSS port wing survey
03:00 PM...01...00...15...Mission status briefing on NTV
03:05 PM...01...00...20...OBSS berthing
03:40 PM...01...00...55...OMS pod survey
03:50 PM...01...01...05...Laser data downlink
04:00 PM...01...01...15...Rendezvous tools checkout
04:30 PM...01...01...45...Centerline camera setup
05:00 PM...01...02...15...Orbiter docking system ring extension
05:25 PM...01...02...40...NC-3 rendezvous rocket firing
06:00 PM...01...06...00...Post-MMT briefing on NTV
08:45 PM...01...06...00...Crew sleep begins
09:00 PM...01...06...15...Daily video highlights reel on NTV

03:00 PM, 2/7/08, Update: Shuttle Atlantis rockets into space (UPDATED at 5:25 p.m. with quotes from post-launch news conference; initial debris report)

Running two months late, the repaired shuttle Atlantis thundered safely into orbit today after expected storms from a weakening cold front failed to materialize. The low-level hydrogen fuel sensor circuits that derailed two launch tries in December worked normally today, clearing the way for launch of Atlantis and a European Space Agency research module bound for the international space station.

ÒI think for Europe, it's the start of manned space flight," Hans Schlegel, a German astronaut making his second flight aboard a space shuttle, said late last year. ÒBecause all of the sudden, we have what we are strong in - developing experiments, building experiments to be conducted in space, either in cooperation with NASA or cooperation with the Russian space agency - all of the sudden we have a module of our own which is available to us, to the scientists in Europe, 24 hours (a day), 365 days a year. This will really be the beginning."

With its three main engines at full power, Atlantis' twin solid-fuel boosters ignited with a ground-shaking roar at 2:45:30 p.m., instantly pushing the spacecraft away from pad 39A atop churning pillars of brilliant flame and exhaust. As with all flights to the space station, launch was timed to roughly coincide with the moment Earth's rotation carried the pad into the plane of the space station's orbit.

Initially climbing straight up through a partly cloudy sky, Atlantis wheeled about its long axis 10 seconds after liftoff, putting the crew into a heads-down orientation, and arced out over the Atlantic Ocean on a northeasterly course paralleling the east coast of the United States.

At the controls were commander Steve Frick, pilot Alan Poindexter, son of Reagan administration National Security Advisor John Poindexter, and flight engineer Rex Walheim. Their crewmates are Leland Melvin, Stan Love and European Space Agency astronauts Schlegel and Leopold Eyharts.

Eight-and-a-half minutes after liftoff, Atlantis slipped into its preliminary orbit. There were no obvious signs of any major losses of foam insulation from the ship's external tank, but analysis of imagery from the shuttle and from ground cameras will take several days to complete.

"It was a pretty clean launch," astronaut Jim Dutton radioed from mission control about two-and-a-half hours after takeoff. "We did see, at about MET 2:13 (two minutes 13 seconds after launch) a few piece of debris, they think at least three, that came off inboard of the LO2 (liquid oxygen) feedline just aft of the starboard bipod leg. The debris assessment team indicated they didn't identify an impact at the time and it's obviously under evaluation."

"OK, thanks for that report," Frick replied. "We really appreciate it."

Bill Gerstenmaier, chief of space operations at NASA headquarters in Washington, said the debris was "fairly small foam loss compared to what we've seen in the past."

The astronauts plan to carry out an inspection of the shuttle's nose cap and wing leading edge panels Friday, a now-routine post-Columbia check to look for signs of ascent debris damage. Atlantis' heat-shield tiles will be inspected Saturday during final approach to the space station.

If all goes well, Atlantis will dock with the outpost around 12:25 p.m. Saturday, marking the station crew's second docking in as many days. Earlier today, an unmanned Russian Progress supply ship, launched from the Baikonur Cosmodrome in Kazakhstan on Tuesday, successfully docked with the lab complex at 9:30:13 a.m. Launch originally was planned for today, but the flight was moved up two days to accommodate Atlantis.

Eyharts, veteran of a stay aboard the Russian Mir space station in the 1990s, will remain behind aboard the international lab complex when Atlantis departs, replacing astronaut Dan Tani as a member of the Expedition 16 crew and joining station commander Peggy Whitson and Yuri Malenchenko as a full-time station crew member.

Along with delivering the Columbus research module to the lab complex, Atlantis also is carrying presents for Whitson, who will celebrate her 48th birthday Saturday. But the clear stars of the show today were Atlantis and Columbus.

"Obviously, a real thrill to be here again on one of the more significant shuttle launches we'll ever have," NASA Administrator Mike Griffin said during a post-launch news conference. "I often am asked with regard to space station assembly, what is the most significant launch, or what is the most crucial launch or something like that. ... The answer we always give is there is no one launch that's more significant than the others because the space station, to function, requires every single launch to go well.

"But certainly, no launch can be any more momentous than the launch of Columbus, which brings to the space station truly international capability and participation. It shows visibly and in actuality that this is a real partnership among nations and among societies to bring together a capability greater than any one nation could bring by itself."

Jean-Jacques Dordain, director general of the European Space Agency thanked Griffin for the ride to orbit.

"It's a great day for ESA," he said. "I think that from now on, ESA is a visible and complete partner of the international space station. That's not to say we were absent so far, but we were more around tables for discussions than in orbit. Now we have a big piece, we have our laboratory in orbit. I would like first to thank NASA, because they have made the job today. We at ESA today, we were more observers than actors and they have done the job, including influencing the weather!"

Atlantis originally was scheduled for launch Dec. 6, but the flight was delayed because of intermittent electrical continuity in wiring leading to low-level hydrogen fuel sensors in the base of the shuttleÕs external tank. A second launch try Dec. 9 also ended in failure and the mission was put on hold pending a fueling test Dec. 18 and work to pin down the cause of the engine-cutoff Ð ECO Ð sensor problems.

The four ECO sensors are part of a backup system intended to make sure the shuttle's main engines don't suck a tank dry after some other problem - a leak, for example, or an improper hydrogen-oxygen mixture ratio - used up propellant at faster than normal rates. An engine running out of hydrogen during normal operation likely would suffer a catastrophic failure.

Data collected during the Dec. 18 fueling test indicated the problem was the result of temperature-induced circuit-breaking gaps in the pins and sockets on the external side of a feed-through connector that carries signals to and from the sensors through the wall of the tank.

The solution was to solder the external pins and sockets together, eliminating any gaps that could lead to a loss of connectivity. Testing at cryogenic temperatures indicated the fix was successful and during fueling today, all four circuits performed normally, operating as required during a series of tests to confirm their health.

But it took two months to resolve the problem and Tani, who originally planned to return to Earth aboard Atlantis in December, was forced to extend his stay in space. Sadly, he was off the planet when his mother was killed in a Chicago-area car-train crash Dec. 19.

The ECO sensor problem and two-month launch delay came at a critical moment in space station assembly. Going into Atlantis' December launch campaign, Whitson, Malenchenko and Tani had just wrapped up a grueling few weeks of work to ready the station for arrival of Columbus and two Japanese modules originally scheduled for launch in February and April.

The delay for Atlantis pushed the next flight - shuttle Endeavour and the first of the two Japanese modules - from Feb. 14 to mid March. Launch of the shuttle Discovery with the second Japanese research lab remains on track for April 24, but Atlantis' next flight, a final mission to service the Hubble Space Telescope, is expected to slip from Aug. 7 to around the end of the month.

The final two flights of the year, a space station logistics and resupply mission by Endeavour and delivery of a final set of solar arrays, are expected to slip about a month, to mid October and early December respectively. Griffin said today he is optimistic the agency has enough margin to complete the station and retire the shuttle in 2010 as planned.

"I don't think we can have too many more stand-down problems," Griffin told CBS News in an interview. "But where we are today, our schedule shows finishing up in April of 2010. We've still got five months margin. ... So I think we're in good shape. If we fly four-and-a-half flights a year from now until the next, you know, two-and-a-half years, we're done and we're done on time."

The Atlantis astronauts plan to attach the Columbus module to the newly installed Harmony module's right-side port on Feb. 10, the day after docking.

The 22.5-foot-long module weighs some 28,200 pounds and adds 2,600 cubic feet of volume to the station. Built by EADS Space Transportation, Columbus will be launched with four European science racks and one European storage rack in place. NASA later will install five racks of its own. The European Space Agency has spent about $2 billion building Columbus, the experiments that will fly in it and the ground control infrastructure necessary to operate them.

"The laboratory modules are why we're doing it," Griffin said. "On the space station, it's really two things. It's a place to learn how to live and work in space, which we need to do, and for a long period of time before we go to Mars. It's also a place to do the research we would like to do in a better way than we've been able to do it in the more confined places we've flown in before.

"So now, more than a fourth of our laboratory capacity on the station as a whole is going up on this flight. It puts the Europeans into human spaceflight in a visible and permanent way. As you say, it makes the station a truly international collaboration, just every thing about it is good."

Three spacewalks are planned for the Atlantis mission, two by Walheim and Schlegel and one by Walheim and Love.

During the first excursion Feb. 10, the day after docking, Walheim and Schlegel will attach a robot arm attachment fitting to Columbus, disconnect power cables from the new module, remove docking port covers and make preparations for a second spacewalk two days later. Melvin, meanwhile, will use the station's robot arm to move Columbus from its perch in the shuttle's cargo bay to its mounting point on the right side of Harmony. It will be locked in place by 16 motorized bolts.

If all goes well, Eyharts will float into Columbus for the first time the next day, on Feb. 11, and begin initial outfitting. The day after that, Walheim and Schlegel will venture back outside to replace a spent nitrogen tank in the main solar power truss that was used to push ammonia coolant through the supply and return lines leading to and from Harmony. The old nitrogen tank assembly will be moved to the shuttle's cargo bay for return to Earth.

A third spacewalk by Walheim and Love is planned two days later, on Feb. 14, to mount two European experiment facilities on the outboard bulkhead of the Columbus module and to move a failed control moment gyroscope from a storage platform on the station to Atlantis for return to Earth.

As it currently stands, Atlantis will land back at the Kennedy Space Center around 10 a.m. on Feb. 18. But NASA managers are holding open the option of extending the flight by one day to give Eyharts more time to complete initial commissioning of the new research lab.

12:30 PM, 2/7/08, Update: Griffin pleased with ECO recovery work; downplays concern about Ares 1 rocket

NASA Administrator Mike Griffin, in an interview with CBS News today, said he remains optimistic the agency can complete the international space station and retire the shuttle as planned by the end of fiscal 2010 despite recent delays to recover from hail damage and problems with critical fuel sensors.

Griffin also said recent questions about high vibration levels in the Ares 1 rocket NASA is building to carry astronauts into low-Earth orbit for eventual flights to the moon will be successfully resolved, saying claims to the contrary are unfounded.

Griffin discussed these and other issues with CBS News space analyst William Harwood before today's attempt to launch Atlantis on a delayed station assembly mission.

Q: It appears the engine cutoff sensors are working properly today. That must be a relief, although I know you were confident going into fueling.

A: I followed every step in the debugging and fixing ... the problem, so I had real good confidence it was going to work and it did today. So yeah, I think we fixed it and one more source of launch delays off the books now.

Q: But the problem and the difficulty you had resolving it illustrates the overall complexity of the shuttle.

A: Boy, no kidding.

Q: NASA lost several months last year recovering from hail damage to an external tank, and Atlantis is two months late because of problems with the engine cutoff (ECO) sensors. How confident are you about meeting the 2010 deadline for station assembly? It strikes me you can't have too many more stand downs and still make that target.

A: Well, you're right, I don't think we can have too many more stand-down problems. But where we are today, our schedule shows finishing up in April of 2010. We've still got five months margin until the end of the fiscal year (2010) and it's pretty darn rare to get a new budget, which is our real guideline, it's pretty darn rare to get a new budget on Sept. 30th anyway. So I think we're in good shape. If we fly four-and-a-half flights a year from now until the next, you know, two and a half years, we're done and we're done on time.

Q: So you're optimistic you can pull this off? A: I am. I really am. I think we now understand foam (shedding), that's behind us, the new ice-frost ramp design is coming on line, we understand why the old one works as well as it did. I think we've got foam behind us. I was the guy who took to calling these ECO sensors the 'launch prevention devices,' which gained a certain amount of currency among the team. But that's behind us. We're not working any other hardware problems that we know of today. It's down to weather.

Q: Launching the Columbus research module is a huge step for the European Space Agency...

A: Enormous.

Q: How important is it to NASA to get Columbus and Japan's Kibo modules up and running? A: The laboratory modules are why we're doing it. On the space station, it's really two things. It's a place to learn how to live and work in space, which we need to do, and for a long period of time before we go to Mars. It's also a place to do the research we would like to do in a better way than we've been able to do it in the more confined places we've flown in before. So now, we're getting more than a fourth of our laboratory capacity on the station as a whole is going up on this flight. It puts the Europeans into human spaceflight in a visible and permanent way. As you say, it makes the station a truly international collaboration, just every thing about it is good.

Q: That obviously holds for Kibo as well, in your view.

A: That's just the easiest question in the world to answer. Yeah, Kibo two flights from now puts the Japanese into human spaceflight in a big way and adds another, more than a fourth of our laboratory capacity. The station is really coming together over this next year or so.

Q: Of course, it takes electrical power to support those new modules and the station has been having problems with the right side of the main solar power truss. How confident are you engineers will figure out a solution to either fix the solar alpha rotary joint (SARJ) or move the drive mechanism over to a different race ring? A: They can resolve it. We don't need all the power right away anyway. I mean, if they have to, they can replace the whole thing. The more interesting question is why it happened. We're still trying to pin that down. ... I wouldn't say yet that we really understand it. That said, we probably are going to go to the inner race ring and solve it that way.

Q: It's an unsual problem.

A: It strikes us as very odd as well. Again, you are so right, we don't have anybody on the team that thinks they're ready to raise their hand and say 'I understand this.'

Q: After you launch the international lab modules, it's time to fly the only non-station flight left on the schedule: a mission to service the Hubble Space Telescope. What's your confidence level going into that very complex flight?

A: All of the Hubble servicing missions have been challenging from the very first. But we have got a great crew, a great ground team at Goddard and Johnson on this and I'm really confident on that flight. I'm very confident those guys are going to do great.

Q: On a different topic, the Ares rocket and the Constellation program continue to generate questions among outside observers as to viability of the rocket system, due to vibration and other issues, and the overall architecture of the moon program. Why is that? A: Let me get down to the bottom of it. There were winners and losers in the contractor community as to who was going to get to do what on the next system post shuttle. And we didn't pick (Lockheed Martin's) Atlas 5, in consultation with the Air Force for that matter, because it wasn't the right vehicle for the lunar job. Obviously, we did pick others. So people who didn't get picked see an opportunity to throw the issue into controversy and maybe have it come out their way.

In point of fact, the thrust oscillation, as it's called, on Ares 1 is not a significant problem and to the extent that it needs solutions, we've got three or four ways to go after it. We can put damping mechanisms between the first and second stage, beteween the second stage and Orion or within Orion itself to locally isolate things. This is something that's done on almost all of our unmanned vehicles, they have solid strap-ons and this thrust oscillation issue is one of the vibration drivers on most satellite vehicles and the satellites designed to fly on them have damping and isolation devices at the frequencies of interest, and that's what we'll do here. I think you have been around long enough to know technically this is just not a big deal. It's about winners and losers. In the larger context, it's about winners and losers and people seeing an opportunity to reclaim a share of the pie that was lost. And I hate it when it comes to that. But that's it. The fact of the matter is, Ares, the rocket, and Constellation, the program, are designed to go to the moon and to provide a capability, if necessary, to service the space station in Earth orbit.

The Atlas 5 needs substantial upgrades in order to be a useful part of the lunar architecture and those upgrades, when we added them all up, cost more than the Ares 1. It's that simple. Now if you just want to go to low-Earth orbit and nowhere else, then the Atlas 5 will do just fine. And I encourage its use for that. What I don't encourage is for people to say that going to low-Earth orbitÊand stopping there again is a good goal. That's not what we're tyring to do. We're trying to get back to the moon and we want to go on to Mars. And that needs something bigger.

11:30 AM, 2/7/08, Update: Astronauts strap in for launch

Shuttle commander Steve Frick, Alan Poindexter, Rex Walheim, Leland Melvin, Stan Love and European Space Agency astronauts Hans Schlegel and Leopold Eyharts began strapping in aboard Atlantis shortly after 11 a.m. to prepare for launch on a space station assembly mission.

There are no technical problems of any significance at pad 39A and the four low-level hydrogen sensors at the base of the shuttle's external tank continue to operate normally. But low clouds from a slowly approaching cold front are building up to the west, threatening to produce a broken deck of clouds as the day wears on that would violate NASA's launch weather rules.

As of this writing, it's too soon to say how the weather might play out and NASA is pressing ahead with today's launch attempt. Launch is targeted for 2:45:30 p.m., one second later than earlier estimates.

8:40 AM, 2/7/08, Update: Fueling complete; ECO sensors operating normally

The shuttle Atlantis' external tank was loaded with a half-million gallons of super-cold liquid oxygen and hydrogen rocket fuel today and after an extensive series of tests, engineers confirmed the four engine cutoff - ECO - sensors at the base of the tank are working normally.

Problems with the ECO sensor circuits grounded Atlantis in December but a modified wiring connector that passes signals to and from the sensors through the wall of the tank aappears to be working properly today, with no signs of any temperature-induced open circuits, or loss of continuity.

"Once we got fully tanked, around 8:15, we went to a sensor confidence test ... and I'm pleased to say all the sensors functioned as designed and we have a good ECO system and we're ready to go fly," said Launch Director Doug Lyons. "Now, we'll continue to monitor the system throughout the countdown. A final confidence check is performed at T-minus nine minutes but again, we have high confidence that that'll be successful."

The automated fueling procedure began at 5:21 a.m. and ended around 8:20 a.m. when the tank went into "stable replenish" mode.

The hydrogen ECO sensors, part of a backup system designed to ensure a normal engine shutdown if some other problem threatens to drain the tank faster than expected, were submerged in liquid hydrogen around 5:54 a.m. Shortly thereafter, engineers began sending computer commands to simulate a dry state to verify the sensors circuits are working properly.

Initial checks went well, but engineers held off on declaring success until after the tank was fully loaded with propellant.

There are no technical problems of any significance at pad 39A and the only concern as of this writing is the weather, with forecasters tracking low clouds and rain from an approaching cold front. While the official forecast calls for a good chance of rainy weather, NASA managers are pressing ahead in hopes the timing of the front's arrival might permit liftoff.

7:00 AM, 2/7/08, Update: ECO sensors pass initial health checks

Initial health checks show all four low-level hydrogen fuel sensors at the base of the shuttle Atlantis' external tank are operating normally, indicating a redesigned connector used to pass signals from the sensors out of the tank is working as expected.

"All of the pre-planned tests that the test team has been doing here in the firing room have been completed and so far, all of the sensors are performing as they should," said launch commentator George Diller. "However, there are some tests that the system will be going through automatically on its own once we enter stable replenish (when the shuttle's exgternal tank is fully loaded with rocket fuel).

"And when that occurs (around 8:20 a.m.), if all of our sensors still are operating properly that would be a pretty good point at which to say we know we've got four good sensors. ... Right now, we're past the point where we've had problems before. All of the sensors right now appear to be looking like they are operating as they should."

Temperature-induced gaps between pins and sockets in the connector are believed to have caused the open circuits that derailed two launch attempts Dec. 6 and 9. The solution was to solder the pins and sockets together to eliminate any possible gap opening.

Shuttle fueling began at 5:21 a.m. today and by 5:54 a.m., enough liquid hydrogen was in the tank to cover the sensors, subjecting the circuits to a minus 423-degree Fahrenheit shock. All four sensors indicated a transition to the wet state and shortly thereafter, engineers began sending a carefully scripted set of computer commands to simulate the dry conditions of an empty tank.

It was at this point during Atlantis' previous launch attempts that problems developed, with multiple sensors failing to indicate the change in state. While all four sensor circuits appeared to respond properly today, Diller said additional tests will be conducted throughout the countdown with a final "sim dry" check during a hold at the T-minus nine-minute mark. Readings from the sensors will be monitored all the way up to T-minus 31 seconds when Atlantis' flight computers take over the countdown.

5:30 AM, 2/7/08, Update: Shuttle fueling begins; weather remains a concern

Hoping for a break in the weather, NASA's Mission Management Team cleared engineers at the Kennedy Space Center to fuel the shuttle Atlantis for launch on a long-awaited space station assembly mission. The three-hour fueling procedure began on time at 5:21 a.m., setting up a launch attempt at 2:45:29 p.m.

The same cold front that wreaked havoc across the southeastern United States earlier this week was about 70 miles northwest of the space center when fueling began and forecasters predict the frontal boundary will be close to or right on top of the spaceport this afternoon. While forecasters are still predicting a 70 percent chance of showers and possible thunderstorms that would delay launch, there is some uncertainty about the timing of the front's arrival and the MMT decided to press ahead in hopes for a break in the cloud cover.

There are no technical problems of any significance at launch pad 39A and engineers remain confident a modified engine cutoff - ECO - sensor circuit connector will work properly today. Temperature-induced problems with the connector are believed to have caused the loss of continuity that derailed launch attempts Dec. 6 and 9.

The four sensors in question will be submerged in liquid hydrogen by around 6:05 a.m. and engineers will carry out tests shortly thereafter to confirm their health. While the countdown can proceed in the event of a single circuit failure, any such malfunction would have to be understood and not involve the redesigned connector.

Here is a timeline of today's countdown (in EST):

EST...........EVENT

05:21 AM......Oxygen (LO2), hydrogen (LH2) transfer line chilldown
05:30 AM......Main propulsion system chill down
05:30 AM......LH2 slow fill
06:00 AM......LO2 slow fill
06:05 AM......Hydrogen ECO sensors go wet
06:10 AM......LO2 fast fill
06:20 AM......LH2 fast fill
08:15 AM......LH2 topping
08:20 AM......LH2 replenish
08:20 AM......LO2 replenish

08:20 AM......Begin 2-hour 30-minute built-in hold (T-minus 3 hours)
08:20 AM......Closeout crew to white room
08:20 AM......External tank in stable replenish mode
08:35 AM......Astronaut support personnel comm checks
09:05 AM......Pre-ingress switch reconfig
09:25 AM......Crew breakfast/photo op (recorded)
09:45 AM......NASA television launch coverage begins
10:15 AM......Final crew weather briefing
10:25 AM......Crew suit up begins
10:50 AM......Resume countdown (T-minus 3 hours)

10:55 AM......Crew departs O&C building
11:25 AM......Crew ingress
12:15 PM......Astronaut comm checks
12:30 PM......Hatch closure
01:10 PM......White room closeout

01:30 PM......Begin 10-minute built-in hold (T-minus 20m)
01:40 PM......NASA test director countdown briefing
01:40 PM......Resume countdown (T-minus 20m)

01:41 PM......Backup flight computer to OPS 1
01:45 PM......KSC area clear to launch

01:50 PM......Begin final built-in hold (T-minus 9m)
02:21 PM......NTD launch status verification
02:36:25 PM...Resume countdown (T-minus 9m)

02:37:55 PM...Orbiter access arm retraction
02:40:25 PM...Launch window opens
02:40:25 PM...Hydraulic power system (APU) start
02:40:30 PM...Terminate LO2 replenish
02:41:25 PM...Purge sequence 4 hydraulic test
02:41:25 PM...Navigation system activated
02:41:30 PM...Aerosurface profile
02:41:55 PM...Main engine steering test
02:42:30 PM...LO2 tank pressurization
02:42:50 PM...Fuel cells to internal reactants
02:42:55 PM...Clear caution-and-warning memory
02:43:25 PM...Crew closes visors
02:43:28 PM...LH2 tank pressurization
02:44:35 PM...Booster joint heater deactivation
02:44:54 PM...Shuttle flight comptuers take control of countdown
02:45:04 PM...Booster steering test
02:45:18 PM...Main engine start (T-6.6 seconds)
02:45:25 PM...Booster ignition (LAUNCH)

10:25 AM, 2/6/08, Update: Weather forecast now 70 percent 'no go' for Thursday launch

A killer cold front that swept through the southeastern United States Tuesday will lose much of its punch by the time it reaches central Florida on Thursday, but shuttle forecasters say they now expect a 70 percent chance of rain and possible thunderstorms that would delay Atlantis' launch on a space station assembly mission.

Shuttle weather officer Kathy Winters said the outlook improves to 60 percent "go" on Friday with a 70 percent chance of acceptable conditions on Saturday.

"I wish I had a better weather report for tomorrow, but we are expecting to have some significant weather in the area," Winters said. "We expect to see some cumulus clouds developing in the area, possibly some showers and there's even a potential for an inland thunderstorm. Our concern with that would be an (electrically charged) anvil coming across ... into the area. That would be a violation of one of our triggered lightning launch commit criteria. So we do have a lot of concerns for launch tomorrow."

NASA Test Director Jeff Spaulding said the shuttle's countdown is proceeding smoothly with no technical problems of any significance. Engineers loaded liquid hydrogen and oxygen aboard the orbiter Tuesday afternoon to power the ship's electrical generators, completed main engine checkouts overnight and are wrapping up inspections of the external fuel tank.

NASA's Mission Management Team will meet at 4:45 a.m. Thursday to assess the weather and to give the launch team clearance to begin fueling. The three-hour procedure is scheduled to begin around 5:20 a.m. and launch remains targeted for a five-minute period beginning at 2:45:25 p.m.

03:07 PM, 2/5/08, Update: Cain confident ECO sensors will work properly

LeRoy Cain, manager of shuttle integration at the Kennedy Space Center, said today he is confident the redesigned connectors intended to fix on-going problems with low-level fuel sensors in the shuttle Atlantis' external tank will work properly Thursday when the ship is fueled for takeoff. But engineers will be paying close attention to the sensors and if any problems develop that might cast doubt on the fix, the shuttle will remain on the ground.

"We expect to see the system work perfectly normally and we expect to see completely nominal results when we ... cover up the sensors and they're initially wetted (with super cold liquid hydrogen rocket fuel)," Cain said. "If they see any failures, we'll respond to those per the pre-planned contingency procedures. But I expect to see a completely nominal system, I have very high confidence that the resolution we came to here on this system is very solid."

The space shuttle's external tank is equipped with a variety of propellant level sensors, including four at the bottom of the hydrogen section that are known as engine cutoff - ECO - sensors. The ECO sensors serve as a backup system to make sure a shuttle doesn't run out of fuel while the engines are still running because of some other problem.

During attempts to launch Atlantis on Dec. 6 and 9, multiple ECO sensor circuits failed to work properly. Subsequent analysis, including results of a fueling test Dec. 18, indicated the problems were the result of temperature-induced gaps in the pins and sockets of a connector that routes sensor data out of the tank to the shuttle.

The solution was to solder the connector pins and sockets together, eliminating any possibility of more open circuits when the hardware is chilled to liquid hydrogen temperatures.

NASA managers are so confident the fix will work, they agreed to use the normal launch commit criteria, which calls for three of the four ECO sensors to be operational for a launch to proceed. But Cain said any failure Thursday will be closely scrutinized to make sure it's not something that could affect the other sensors or is the result of a problem with the redesigned connector.

"What we have put in place from a launch commit criteria standpoint is we can go fly safely with three of four functioning LH2 engine cutoff sensor circuits," Cain said. "In that case, however, the one failure that we've suffered, we need to understand it well enough to be able to say it's not potentially a generic problem or it's not some problem that could somehow be associated with this failure mode that we think we just fixed.

"So, if the one failure that we see somehow potentially indicts the failure mode that we believe we just mitigated with this new connector hardware, then we're not going to be 'go' to launch in that case. But if it's a problem that associated with an MDM (multiplexer-demultiplexer), a multiplexer card or some other part of the system that we can positively identify that ... would not indict this fix we just put in place, then from an overall safety of the system ... standpoint, then we've said we're good to go with three of four. But it has to be in those circumstances."

And only one sensor can fail. If two circuits malfunction for any reason, launch will be scrubbed.

"We'll be keeping a close eye on our ECO sensors," said Launch Director Doug Lyons. "The program's given us clear direction on our LCCs and so we would be no go at that point. ... We're done with two (failures)."

Atlantis' countdown began Monday afternoon, setting up a launch attempt at 2:45:25 p.m., roughly the moment Earth's rotation carries pad 39A into the plane of the international space station's orbit. Forecasters are predicting a 60 percent chance of stormy weather from a passing cold front, but conditions are expected to improve to 80 percent "go" Friday and Saturday.

Engineers plan to begin pumping liquid hydrogen into the external tank around 5:20 a.m. Thursday. The four ECO sensors will "go wet," or be submerged in hydrogen, around 6:05 a.m. Shortly thereafter, engineers will send commands to simulate "dry" sensors and then monitor the circuits to make sure they respond properly. Additional tests are planned throughout the countdown with a final check during a hold at the T-minus nine-minute mark.

The goal of the delayed mission is to deliver the European Space Agency's Columbus research module to the international space station. Alan Thirkettle, space station program manager for the European agency, said it is "terribly important" to get Columbus into orbit, but he said he agreed with the decision to delay the flight when the ECO sensors acted up in December.

"If we'd launched in December, we wouldn't have anything to look forward to on Thursday," he joked. "So, you have to take the positives on these things! We've indeed waited a long time for this launch and it's just going to make it all the better when it gets up there and it works.

"We know the business that we're in. We know the people that we're dealing with, we know the systems that we're dealing with. It's terribly important for us to fly, but it's even more important for us to fly safely. And that's always been the line that we've taken. It would not have been prudent to fly in December, the right decisions were taken at the right time. Hopefully on Thursday we'll get through and we'll get the mission we've all been looking for."

10:20 AM, 2/5/08, Update: Countdown on track

The shuttle Atlantis' countdown continues to tick smoothly toward launch Thursday, with engineers gearing up to pump hydrogen and oxygen into the shuttle this afternoon to power the ship's fuel cell system. There are no technical problems of any significance at pad 39A and the only concern as of this writing is the weather, with forecasters continuing to predict a 60 percent chance of rain and possible thunderstorms from a passing cold front that could cause a delay.

"For launch, the front will be just about overhead," said Mike McAleenan, launch weather officer at the 45th Weather Squadron at Patrick Air Force Base. "We're looking for some significant amount of cloud cover and maybe a 60 percent chance of KSC weather prohibiting launch.

Depending on the timing of the front's passage, forecasters expect "possible crosswind violation, cumulus rule violation, anvil and rain showers in the area," McAleenan said.

But the forecast improves to 80 percent "go" Friday and Saturday.

"We're hopeful we can find a hole on Thursday," McAleenan said. "If not, Friday certainly looks good."

Otherwise, NASA Test Director Steve Payne said the countdown is proceeding smoothly and "we have no problems to report. ... We're all looking forward to Thursday afternoon's launch."

5:05 PM, 2/4/08, Update: Countdown begins

The shuttle Atlantis' countdown began today for launch Thursday on a space station assembly mission. The countdown began on time at 5 p.m., setting up a launch attempt at 2:45:25 p.m. Thursday, roughly the moment Earth's rotation carries pad 39A into the plane of the space station's orbit. There are no technical problems as of this writing, but the weather remains a concern with forecasters predicting a 60 percent chance of rain from a passing cold front. The forecast improves to 80 percent "go" Friday and Saturday.

Here are the latest "in-plane" launch times for Thursday, Friday and Saturday (in EST):

DATE.......WINDOW OPEN...LAUNCH........WINDOW CLOSE..STATION DOCKING

02/07/08...02:40:25 PM...02:45:25 PM...02:50:25 PM...Flight Day 3
02/08/08...02:14:46 PM...02:19:46 PM...02:24:46 PM...FD-3
02/09/08...01:52:11 PM...01:57:11 PM...02:02:11 PM...FD-3

12:00 PM, 2/4/08, Update: STS-122 mission preview

Running two months late, the shuttle Atlantis and its crew are set for blastoff Thursday on a long-awaited flight to attach the European Space Agency's Columbus research lab to the international space station. The module represents EuropeÕs first manned toehold in orbit and promises to open a new era of international research with Japanese lab modules scheduled to follow in March and April.

"I think for Europe, it's the start of manned space flight," said Hans Schlegel, a German astronaut making his second flight aboard a space shuttle. "Because all of the sudden, we have what we are strong in - developing experiments, building experiments to be conducted in space, either in cooperation with NASA or cooperation with the Russian space agency - all of the sudden we have a module of our own which is available to us, to the scientists in Europe, 24 hours (a day), 365 days a year. This will really be the beginning."

Said NASA Administrator Mike Griffin: "Reaching this point is a tremendous milestone for NASA and the space station program. I mean at one stroke, we almost double the laboratory capacity on board. It's a new, modern, state-of-the-art laboratory, several years newer in the end than the U.S. lab. It makes a real international partnership come to fruition in the form of real hardware.

"We want to take this partnership with us back to the moon, and that wasn't going to happen unless and until we finish up our obligations on the space station and made a real working vehicle out of it," Griffin said in an interview. "Columbus (is) a huge step toward making that happen. Until we actually set out for the moon again, this is as good as it gets."

With commander Steve Frick and pilot Alan Poindexter at the controls, Atlantis is scheduled to lift off from pad 39A at the Kennedy Space Center at 2:45:28 p.m. Thursday, roughly the moment when Earth's rotation carries the launch pad into the plane of the space station's orbit. Their crewmates are flight engineer Rex Walheim, Leland Melvin, Stan Love and European astronauts Schlegel and Leopold Eyharts, a French air force general hitching a ride to the space station.

Liftoff originally was planned for Dec. 6, but the flight was delayed because of intermittent electrical continuity in wiring leading to low-level hydrogen fuel sensors in the base of the shuttleÕs external tank. A second launch try Dec. 9 also ended in failure and the mission was put on hold pending a fueling test Dec. 18 and work to pin down the cause of the engine-cutoff Ð ECO Ð sensor problems.

The four ECO sensors are part of a backup system intended to make sure the shuttle's main engines don't suck a tank dry after some other problem - a leak, for example, or an improper hydrogen-oxygen mixture ratio - used up propellant at faster than normal rates. An engine running out of hydrogen during normal operation likely would suffer a catastrophic failure.

The 10 wires that carry signals from all four ECO sensors and a 5 percent sensor pass through the same connector in the wall of the external tank. The three-part 37-pin connector (27 pins are not used) features a pass-through fitting with gold-plated male pins on both sides.

Wires from the sensors inside the tank terminate in a female connector that is plugged into the male pins of the pass-through. Those pins are imbedded in a glass matrix. A similar female socket plugs into the pass-through on the outside of the tank where the pins are mounted in a Teflon insert.

Data collected during the Dec. 18 fueling test indicated the problem was the result of temperature-induced circuit-breaking gaps in the pins and sockets on the external side of the feed-through connector when the system was chilled to ultra-low temperatures.

To make sure, the feed-through plate with the external connector still attached was removed and shipped to the Marshall Space Flight Center in Huntsville, Ala., for additional testing at cryogenic temperatures. When the hardware was submerged in liquid hydrogen, engineers saw the same sort of open circuits that cropped up during the December launch attempts.

The solution was to solder the external pins and sockets together, eliminating any gaps that could lead to a loss of connectivity. Testing at cryogenic temperatures indicates the fix was successful.

"I'm sure everyone has heard an awful lot about those sensors, but we really rely on them," Frick told reporters at the Kennedy Space Center. "We use virtually all of our gas just to get up to orbit for a normal mission, like 99-and-a-half percent, and we can't afford to let the engines run dry because they tend to come apart. So the ECO sensors are a critical safety system that I'm very happy we were able to fix them and feel very confident about them working."

Shuttle Program Manager Wayne Hale described the soldered connector as "a good solid repair," saying "we have a lot of testing that's gone on to prove that this fix is a good fix, does not entail any unanticipated consequences and will provide us with a reliable safety system in the low level cutoff protection world."

"The work is complete on the vehicle at the launch pad and we're beginning to implement that fix on subsequent tanks so that we won't ever have to talk about engine cutoff sensors again," he said.

NASA's original ECO sensor launch commit criteria required three of the four circuits to be operational for a launch to proceed. That rule later was changed to four-of-four because of concern about a common component that, should it fail, could take out two circuits. That design flaw was addressed before Columbia's last flight and NASA managers eventually changed the flight rule back to requiring three of four operational circuits.

That's the rule that was in place for Atlantis's initial launch try, but it was amended to four of four for the second attempt, primarily because engineers did not yet know what was causing the problem.

Now that testing indicates the problem has been resolved, NASA managers have agreed to go back to the three-of-four criteria, "which is the design intention for that system," Hale said.

"On this first tanking with the new system in place we're going to watch it very closely to ensure that we really have eliminated the common cause mechanism," he said. "If there are any funnies that happen, they will be scrutinized very carefully. ... I expect when we go tank up the vehicle next Thursday we'll be in good shape to go fly."

The ECO sensor problem and two-month launch delay came at a critical moment in space station assembly. Going into Atlantis' December launch campaign, Expedition 16 Commander Peggy Whitson, cosmonaut Yuri Malenchenko and astronaut Dan Tani had just wrapped up a grueling few weeks of work to ready the station for arrival of Columbus and two Japanese modules originally scheduled for launch in February and April.

The delay for Atlantis pushed the next flight - shuttle Endeavour and the first of the two Japanese modules - from Feb. 14 to mid March. Launch of the shuttle Discovery with the second Japanese research lab remains on track for April 24, but Atlantis' next flight, a final mission to service the Hubble Space Telescope, is expected to slip from Aug. 7 to around Aug. 28.

The final two flights of the year, a space station logistics and resupply mission by Endeavour and delivery of a final set of solar arrays, are expected to slip about a month, to mid October and early December respectively. But Hale said he is optimistic NASA can pull off a six-mission year and even if even if additional problems crop up, enough margin remains in the schedule to complete the station and retire the shuttle in 2010 as planned.

"We know that it takes continuous vigilance to maintain a safe flight rate, to fly each and every flight as safely as we possibly can," Hale said late last year. "The shuttle is an extraordinary vehicle with a lot of capability and a lot of flexibility, a huge payload capability, but it takes a lot of attention from a lot of people to make sure we fly safely and we have to watch every little anomaly, every little indication to make sure we continue to fly safely.

In 2008, Hale said, "it's a fairly aggressive schedule (but) we have plenty of margin in our schedule to complete the international space station, meet the president's directive to complete flying (the shuttle) by no later than Sept. 30, 2010, so that the agency can then press on and build the moon ship, the Orion and Ares rockets that will take us past low-Earth orbit and back to the moon and on, potentially, to Mars."

The Atlantis astronauts plan to attach the Columbus module to the newly installed Harmony module's right-side port on Feb. 10, the day after docking.

The 22.5-foot-long module weighs some 28,200 pounds and adds 2,600 cubic feet of volume to the station. Built by EADS Space Transportation, Columbus will be launched with four European science racks and one European storage rack in place. NASA later will install five racks of its own. The European Space Agency has spent about $2 billion building Columbus, the experiments that will fly in it and the ground control infrastructure necessary to operate them.

In addition to delivering Columbus, Atlantis also will ferry Eyharts to the station. The European Space Agency astronaut, veteran of a three-week stay aboard the Russian Mir space station in 1998, will replace Tani aboard the ISS. Tani, who was launched to the station Oct. 23 aboard the shuttle Discovery, will return to Earth in Eyharts' place aboard Atlantis.

For Tani, Atlantis' launch delay translated into an unexpected two-month mission extension. Along with missing the Christmas holidays with his family, Tani was off the planet when his mother was killed in a car wreck Dec. 19. For Eyharts, the launch delay resulted in a shortened mission. He will remain aboard the lab complex with Whitson and Malenchenko until late March, when he will be replaced by NASA astronaut Garrett Reisman.

With less time aloft than he originally expected, Eyharts' primary responsibility will be activating and outfitting Columbus and beginning science operations after Atlantis departs.

"Columbus is mainly scientific module," Eyharts said in a NASA interview. "We will have four European scientific racks, which will allow Europe to perform science during, we hope, at least 10 years in the station. But there will be also American scientific racks which be installed a little bit later in the station. So with the arrival of Columbus, and later on of the Japanese module, we will start the full exploitation of the ISS as a scientific laboratory. And with the arrival of Columbus, Europe will become a co-owner of the ISS.

"Columbus is a first for Europe," he said. "This will be the first time Europe will have a permanent base in space. And of course, this is very important and this is very challenging. So in the future, of course, we hope that this first participation will help in reinforcing our technical expertise and our experience of operations to be able to go further and participate with the future of space exploration, too."

NASA's larger Destiny laboratory module "is really the heart of the space station, the U.S. segment of the space station," Frick said. "It's got laboratory (equipment), payloads, it's got all kinds of science resources, but it also has the heart of the U.S. segment: It has our computers, it has our power distribution, it has all the things we need to keep functioning and keep alive. The Columbus laboratory is really more of a pure laboratory - it has the resources it needs to keep its payloads going and to keep the crew members that are working inside of it healthy and able to do their job. But it relies on the other modules in the U.S. segment for resources like power and cooling and air and those kinds of things."

Preparing the station for Columbus has been a major challenge. The station was designed for the six-port Harmony module - the eventual attachment point for Columbus and Japan's Kibo research lab - to be mounted on the front end of the station, between the U.S. Destiny lab module and the shuttle docking port, known as pressurized mating adapter No. 2.

Harmony was delivered to the station in late October aboard the shuttle Discovery and temporarily attached to the central Unity module's left side hatch. After Discovery departed, Whitson and Malenchenko staged a spacewalk Nov. 9 to disconnect electrical cables from PMA-2. Then, on Nov. 12, the crew used the station's robot arm to detach PMA-2 and robotically connect it to Harmony's outboard port.

Two days later, on Nov. 14, the Harmony/PMA-2 "stack" was detached from Unity and bolted to the front end of the Destiny module. Whitson and Tani then staged spacewalks Nov. 20 and 24 to hook up power cables and connect ammonia supply and return lines between Harmony and the station's main cooling system on the lab's solar power truss. That work, along with internal outfitting, set the stage for Atlantis' launch and installation of the Columbus module.

Adding a new research module to the space station is a major milestone in the lab's evolution. So is adding another ground control center, a state-of-the-art complex in Oberfaffenhofen, Germany, near Munich. With the addition of Columbus, station astronauts will be in daily contact with flight controllers at the Johnson Space Center in Houston, Oberfaffenhofen and Russian ground control in Korolev near Moscow.

"We all come into these space shuttle flights looking at the big element in the payload bay and waiting for the action when we actually install it," said station Program Manager Mike Suffredini. "This flight and the following stage and multiple stages after that will be an extra challenge for us.

"We have been working with our Russian counterparts and our Canadian counterparts for the better part of about seven years and in all that time, we evolved in our operations capability, how we work together. And now we're bringing on another partner, multiple countries, multiple control centers to operate this Columbus module.

"So the very small part you'll see during the docked operations of installing the Columbus module really will just be the tip of the iceberg as we work together in a partnership and move on into the next couple of flights," Suffredini said. "By April, we'll have the (Japanese modules) up and we'll have yet another partner in operation with us. So it's a very exciting time for us in the ISS program."

Three spacewalks are planned for the Atlantis mission, two by Walheim and Schlegel and one by Walheim and Love.

During the first excursion Feb. 10, the day after docking, Walheim and Schlegel will attach a robot arm attachment fitting to Columbus, disconnect power cables from the new module, remove docking port covers and make preparations for a second spacewalk two days later. Melvin, meanwhile, will use the station's robot arm to move Columbus from its perch in the shuttle's cargo bay to its mounting point on the right side of Harmony. It will be locked in place by 16 motorized bolts.

If all goes well, Eyharts will float into Columbus for the first time the next day, on Feb. 11, and begin initial outfitting. The day after that, Walheim and Schlegel will venture back outside to replace a spent nitrogen tank in the main solar power truss that was used to push ammonia coolant through the supply and return lines leading to and from Harmony. The old nitrogen tank assembly will be moved to the shuttle's cargo bay for return to Earth.

A third spacewalk by Walheim and Love is planned two days later, on Feb. 14, to mount two European experiment facilities on the outboard bulkhead of the Columbus module and to move a failed control moment gyroscope from a storage platform on the station to Atlantis for return to Earth.

Going into the mission, the flight plan calls for Atlantis to land back at the Kennedy Space Center around 10 a.m. on Feb. 18. But if there are no major problems in orbit, NASA managers likely will extend the mission by one day to allow extra time for Columbus activation.

Going into the original December launch campaign, NASA managers held open the option of adding a fourth spacewalk to Atlantis' mission. The idea was to carry out additional inspections of the station's right-side solar alpha rotary joint, or SARJ, which is used to rotate outboard solar arrays like a giant paddle wheel to track the sun.

The space station is equipped with two such rotary joints, one on each side of the lab's main power truss. Each joint features two redundant 10-foot-wide gear/race rings and two drive motors, only one of which is engaged at any given time. Twelve so-called trundle bearing assemblies are positioned around one of the two gear races and hold in place with 1,000 pounds of force to allow smooth rotary operation.

The left-side SARJ is rotating normally, but earlier this fall flight controllers noticed unusual vibration and slightly higher current levels in the right-side SARJ. Tani looked inside the joint behind thermal panel No. 12 during an already planned shuttle assembly spacewalk Oct. 28.

He spotted metallic contamination and collected samples using adhesive tape. Those samples later were determined to be made up of race ring material itself. At that point, mission managers decided to lock the starboard SARJ in place to prevent additional damage.

During a second inspection by Tani during a spacewalk Nov. 24, additional contamination was spotted in a different area. Going into the initial attempts to launch Atlantis, engineers still did not know what might be causing the damage or what might be needed to fix it.

Then, on Dec. 8, another problem developed: a bearing motor roll ring module, or BMRRM (pronounced "broom"), failed on a right-side array, preventing the station's flight computers from positioning the affected panel as required to maximize electricity production.

While the SARJ joints on each side of the power truss turn the outboard arrays like giant paddle wheels, completing one full revolution per orbit, each set of arrays also is equipped with a beta gimbal assembly, or BGA, that uses BMRRMs to turn the panels about their long axis in a motion similar to changing the pitch of an airplane propeller.

The port-side of the station's power truss is finished and now features four solar array wings. The BGAs on those four wings are working normally, as is the port-side SARJ.

But only one set of arrays is in place on the right side of the truss and one of them - panel S4-1A - suffered a BGA failure Dec. 8. Engineers initially believed a cable or some other component might have been hit by space debris or a micrometeoroid. But during a spacewalk inspection by Whitson and Tani on Dec. 18, no such damage was found. Subsequent tests showed the problem involved a fault inside the BGA motor assembly itself, the BMRRM.

Facing two major problems on the right side of the station's main power truss, NASA managers worried they might not have enough power to support the addition of the European and Japanese research modules. But after extensive analysis, engineers concluded station assembly could proceed if the faulty BMRRM was replaced. Even then, power conservation measures will be required.

Given the delay getting Atlantis ready for a third launch try, station managers opted to stage a spacewalk Jan. 30 so Whitson and Tani could install a spare BGA motor. The spacewalk was successful and with beta angle positioning restored on the right side of the power truss, the station can generate enough electricity to support the new research labs. As such, there are no plans to add a fourth spacewalk to Atlantis' mission.

The bigger problem - the damage to the starboard SARJ - is not yet understood. The current plan is to possibly lubricate the damaged race in the near term to permit periodic repositionings and then, during a shuttle visit later this fall, move the 12 bearing assemblies and two drive motors to a redundant inboard gear. Switching to the inboard race would take four to five spacewalks. But engineers do not want to consider such a drastic step until they figure out what is causing the problem with the active gear and race ring.

"Without understanding exactly what the problem is, it's hard to drive back through the fault tree and say exactly how it is that we got there," said Kenny Todd, space station integration and operations manager at JSC. "So obviously, this will be an activity that will challenge us.

"But replacing bearings is something we know how to do. Replacing the drive lock assembly is something we know how to do. These are what we term ORUs, orbital replacement units, they exist to be able to be changed out on orbit. We're not treading new ground here when it comes to doing these tasks. They are things that we train for and we understand how to do.

"I think what's going to be important for us is to understand this particular failure enough that when we go to perform that repair we do it in a way that doesn't somehow or another exacerbate this condition on the other ring. But I think without getting a better understanding of how it was that this happened, it's going to be hard for us to say for sure here's what we'll change, here's what we'll do different."

11:30 AM, 2/4/08, Update: Astronauts arrive for Thursday launch; weather an issue

The Atlantis astronauts flew back to the Kennedy Space Center today for the start of a new countdown to launch Thursday on a long-awaited space station assembly mission. Running two months late because of fuel sensor problems that scrubbed two launch attempts in December, the international crew landed at the Florida spaceport just after 10:30 a.m.

"We're feeling very good about this opportunity," commander Steve Frick said at the runway. "We'll keep looking at the weather, but we've very happy about the condition of Atlantis."

The countdown was scheduled to begin at 5 p.m. today with liftoff targeted for 2:45:28 p.m. Thursday. Forecasters are predicting a 60 percent chance of a delay because of rainy weather, but the odds improve to 80 percent "go" on Friday and Saturday after a front moves through the area.

"The weather is looking good the next couple of days, but then by launch day, unfortunately, we do have a frontal boundary that's going to be coming into the area and will be affecting our weather that day," said Kathy Winters, the shuttle weather officer. "So we do have a chance of having some bad weather on launch day. ... The weather does improve, though, the following two days here at Kennedy Space Center."

The only remaining technical issue of any significance was resolved Sunday when engineers successfully coaxed a kinked Freon flex hose to retract when the shuttle's cargo bay doors were closed for flight. The flex hose, one of four that route Freon coolant to and from radiators attached to the inside of the payload bay doors, is not expected to be a problem in orbit.

"All of our systems are in good shape, our countdown work is on schedule and we have no issues to report," said NASA Test Director Charlene Blackwell-Thompson. "Atlantis is ready to go fly ... and we're all looking forward to Thursday's launch."

Atlantis, carrying the European Space Agency's Columbus research module, was originally scheduled for launch to the international space station on Dec. 6. But the flight was delayed by problems with critical engine cutoff - ECO - sensors at the base of the shuttle's huge external tank.

In the wake of a second launch scrub Dec. 9 and a Dec. 18 fueling test, engineers traced the problem to temperature-induced gaps opening up in the connector that routes signals from the sensors to the shuttle. Testing at the Marshall Space Flight Center in Huntsville, Ala., confirmed the nature of the original problem and demonstrated a new connector design, featuring soldered pins and sockets, will work as advertised.

"A lot of people have asked me is it frustrating or difficult for the crew to get so close to launch last time and then have to wait two months to try again," Frick said today. "But ... I was very happy with the way things went. The ECO sensor problem has been nagging us for quite a long time and we were actually very pleased we were able to have it re-occur a couple of times, pull the hardware out, find out what the problem really is and get a chance to fix it properly so we don't have to worry about it."

The four ECO sensors are part of a backup system intended to make sure the shuttle's main engines don't drain a tank dry after some other problem - a leak, for example, or an improper hydrogen-oxygen mixture ratio - used up propellant at faster than normal rates.

"I'm sure everyone has heard an awful lot about those sensors," Frick said, "but we really rely on them. We use virtually all of our gas just to get up to orbit for a normal mission, like 99-and-a-half percent, and we can't afford to let the engines run dry because they tend to come apart. So the ECO sensors are a critical safety system that I'm very happy we were able to fix them and feel very confident about them working.

"Our technicians here at Kennedy and all over the shuttle program - the technicians, the mechanics, the engineers - are, I think, the best there are and they've done just a tremendous job of nailing this thing down and fixing it so that we know we can go fly."

A detailed countdown timeline, the crew's flight plan, NASA's initial mission television schedule and other background are posted on the CBS News STS-122 Quick-Look page:

http://www.cbsnews.com/network/news/space/currentglance.html A detailed mission preview will be posted here shortly.

04:30 PM, 2/1/08, Update: NASA managers opt to press ahead for 2/7 launch pending successful flex hose retraction, final engineering analysis

NASA managers today decided to press ahead with preparations for launch of the shuttle Atlantis Feb. 7 pending final work Monday to make sure a kinked Freon flex hose retracts as required when the ship's payload bay doors are closed for flight.

Assuming no other problems develop, engineers plan to restart Atlantis's countdown at 5 p.m. Monday for a launch attempt at 2:45:28 p.m. Thursday. This will be NASA's third attempt to launch Atlantis on a space station assembly mission following delays Dec. 6 and 9 because of problems with low-level fuel sensors in the shuttle's external tank.

Those problems were traced to a suspect wiring connector at the base of the tank that has since been modified to prevent the sort of intermittent continuity blamed for the December delays. Engineers are confident the sensor circuits will work properly when the tank is fueled for launch Thursday.

The Freon coolant line issue cropped up earlier this week when the shuttle's cargo bay doors were opened for routine payload processing. Engineers noticed one of four metal-jacketed flex hoses that carry Freon coolant to and from radiator panels mounted on the inside of the ship's cargo bay doors was sharply kinked.

The shuttle is equipped with two Freon coolant loops to dissipate the heat generated by the ship's myriad electronic systems. The concern in this case was the possibility that launch vibrations could damage a weakened flex hose enough to cause a leak.

While loss of a Freon coolant loop would not pose a safety of flight risk, it could force mission managers to shorten a mission and extensive tests were ordered to make sure the hose aboard Atlantis will function properly after launch.

As it turns out, engineers discovered a similar kink in a hose aboard Discovery late last year. That hose was removed and subjected to the sort of flexing it could expect to see over about a dozen door opening-closing cycles. A NASA spokesman said the hose continue to work normally with no signs of any internal damage. As a result, NASA managers called off plans for a Saturday engineering meeting and decided to press ahead with launch preparations. When Atlantis's payload bay doors are closed overnight Sunday, engineers will manually guide the kinked line into its storage container, using an improvised tool when the right-side door closes far enough to limit access.

"They'll assist the hose as the door is closing for flight," the spokesman said. "They'll assist it by hand until it gets closed enough and then they'll use this pole. They'll use it as a guide, they won't put any pressure on it."

Assuming the hose retracts as required, engineers will start the countdown as planned Monday afternoon. The issue will be discussed again at management review Tuesday.

An updated countdown timeline, flight plan and other useful information are available on the CBS News STS-122 Quick-Look page:

http://www.cbsnews.com/network/news/space/currentglance.html

5:30 PM, 1/30/08, Update: Satisfied ECO sensor issue resolved, engineers troubleshoot kink in Freon hose; decision expected Saturday on Feb. 7 launch

Exhaustive testing shows the low-level fuel sensor problem that derailed two attempts to launch the shuttle Atlantis in December has been resolved, NASA managers said today, and engineers are confident soldered connectors will prevent a repeat of the open circuits that grounded the ship two months ago. But a decision on whether to press ahead with a third launch try Feb. 7 was put off to Saturday pending results of last-minute troubleshooting to assess the health of a kinked flex hose in the ship's Freon coolant system.

In what engineers thought was an isolated case, a similar kink was noted last year aboard the shuttle Discovery and engineers were somewhat surprised to find another unexpected bend in one of four such hoses aboard Atlantis that leads from the orbiter's fuselage to radiators on the inside of the shuttle's cargo bay doors.

The shuttle's computers and other electronic systems are mounted on cold plates that use circulating water to carry away heat. That heat is then transferred to two Freon coolant loops that, in turn, carry it to the cargo bay radiators for dissipation into space or to an internal system that boils water to accomplish the same goal.

The concern with the kinked line is that launch vibrations, coupled with stress on the line, could cause a leak. That could force the crew to bypass the radiator in question and rely instead on the flash evaporator system, an option that could affect the duration of the mission.

Shuttle Program Manager Wayne Hale told reporters today after an executive-level flight readiness review that he's optimistic the problem will be resolved in time to proceed with launch on Feb. 7, either by agreement to launch Atlantis as is or to simply straighten out the hose before flight.

"I think we'll have a good answer by Saturday," he said. "Since the hose is not leaking now and a sister hose on Discovery did not leak on a number of flights when it was exhibiting this behavior, I'm feeling very positive we'll come to a good conclusion on this. But we have to do our work here and we want to make sure we know what we're doing before we go fly this vehicle."

On a more upbeat note, Hale said engineers are confident the low-level engine cutoff - ECO - sensors at the base of Atlantis' external tank will work properly following replacement of the so-called pass-through wiring connector with a modified design that features soldered pins and sockets.

Launch attempts Dec. 6 and 9 were scrubbed because of open circuits in the ECO sensor system. The ECO sensors serve as a backup to ensure the main engines don't suck a tank dry in the event of some other problem that might cause them to consume hydrogen fuel faster than expected.

Hale said engineers traced the problem to a temperature-induced loss of continuity in the pins and sockets making up the external side of the pass-through connector. By soldering the pins and sockets together, engineers believe they have eliminated the failure mode.

"We had a multi-disciplinary team from a number of NASA centers, as well as a number of contractors, working together in a unified manner and we have come to a root cause, we believe, for our problems that we've been having in those circuits," Hale said. "There is a good solid repair, or fix, technique which has been implemented and we have a lot of testing that's gone on to prove that this fix is a good fix, does not entail any unanticipated consequences and will provide us with a reliable safety system in the low level cutoff protection world.

"The work is complete on the vehicle at the launch pad and we're beginning to implement that fix on subsequent tanks so that we won't ever have to talk about engine cutoff sensors again," he said.

NASA's original ECO sensor launch commit criteria required three of the four circuits to be operational for a launch to proceed. That rule later was changed to four-of-four because of concern about a common component that, should it fail, could take out two circuits. After that issue was addressed, the rule was changed back to requiring three of four operational circuits.

That's the rule that was in place for Atlantis's initial launch try, but it was amended to four of four for the second attempt, primarily because engineers did not yet know what was causing the problem.

Now that testing indicates the problem has been resolved, NASA managers have agreed to go back to the original three-of-four criteria, "which is the design intention for that system," Hale said.

"On this first tanking with the new system in place we're going to watch it very closely to ensure that we really have eliminated the common cause mechanism," he said. "If there are any funnies that happen, they will be scrutinized very carefully. ... I expect when we go tank up the vehicle next Thursday we'll be in good shape to go fly."

Concern about the Freon hose cropped up Tuesday when Atlantis's cargo bay doors were opened for routine payload processing. Engineers noticed one of the two flex hoses leading to the shuttle's right-side radiator had not retracted properly and was bent sharply when it should have been straight.

"This (hose) goes down into a box, it's got some rollers and a spring mechanism to kind of suck this hose down as the payload bay doors close and clearly something is not lining up in that box properly," Hale said. "So we'll figure it out, but today I don't think anybody knows what's causing it."

The hose in question is located under the European Columbus research module bound for the international space station. While engineers may be able to manually straighten the hose, replacing it might not be possible at the launch pad because of access issues and rules governing the release of Freon into the atmosphere. Hale said he is optimistic it won't come to that.

"Right now, that hose is perfectly functional," he said. "We're not leaking, it's in good shape. It's just kind of bending the wrong way. Fortunately, we have the hose we took off the sister ship, Discovery. We now have good knowledge we've flown at least two flights, perhaps more, with this kind of bend in the hose and that hose did not leak. It has been removed from (Discovery) and taken to the Boeing Co.'s laboratories in Huntington Beach, Calif., where we're doing a great deal of work to understand whether or not this is a threat to us. I would repeat again that this hose on Atlantis is not leaking, It's just merely bent the wrong way. So we're trying to understand that."

NASA managers will meet again Saturday to review the troubleshooting and make a decision on whether to press ahead with launch preparations. Liftoff is targeted for 2:45 p.m. on Feb. 7.

"Hopefully, and I'm going to be positive about this, we will come to the conclusion that this is acceptable to fly at least one flight, either exactly like this or potentially, having (to) manually straighten this hose out and then flying it. So that is work ahead of us that we must clear before we go fly."

Otherwise, he said, all systems are go for launch.

"I had a nice discussion with the commander of the flight, Steve Frick, in Houston a few days ago, they're ready to go, all the elements report ready to go and if we didn't have this hose to talk about, it, frankly, would be a little boring."

5:50 PM, 1/11/08, Update: Russian Progress launch moved up; Atlantis retargeted for Feb. 7; station spacewalk on tap

Russian space managers have agreed to move up the launch of an unmanned Progress supply ship by two days to Feb. 5, clearing the way for NASA to retarget launch of the shuttle Atlantis on a twice-delayed space station assembly mission for Feb. 7. NASA managers made the decision Thursday and officially announced it Friday, after consultation with the agency's international partners.

Originally scheduled for launch last month, Atlantis was grounded Dec. 6 and 9 because of intermittent problems with troublesome low-level hydrogen sensors in the ship's external tank. Before the Christmas break, officials said launch was off until at least Jan. 10 and on Jan. 3, the "no-earlier-than" date was moved to Jan. 24.

But resolving the engine cutoff - ECO - sensor problem has been difficult and deputy shuttle Program Manager John Shannon told reporters at that time the launch likely would slip into early February. This week, agency managers decided to move the launch target to Feb. 7 after Russian space officials agreed to move the Progress up two days to Feb. 5.

Assuming the schedule holds up - and on-going tests show an upgraded ECO system wiring connector works as expected - Atlantis would take off around 2:47 p.m. EST on Feb. 7, setting up a docking with the space station around 11:30 a.m. on Feb. 9. Three spacewalks are planned, on Feb. 10, 12 and 14 with undocking on Feb. 16 and landing back at the Kennedy Space Center on Feb. 18.

The two-month launch delay means a flight by the shuttle Endeavour that originally was scheduled for mid February will slip to mid March instead, a ripple effect for other downstream flights. That includes Atlantis' next mission, a long-awaited flight to service the Hubble Space Telescope. Launch had been planned for around Aug. 7 but the flight is now expected to slip to the end of August or into early September.

In the near term, NASA faces a challenging few weeks with a space station solar array motor repair spacewalk planned for around Jan. 30 amid on-going work to install a replacement ECO sensor connector in the wall of Atlantis' external tank.

Data collected during a fueling test last month indicates the open circuits in the ECO sensor wiring that derailed the December launch tries were located in a so-called feed-through connector that routes signals from the sensors inside the tank to the shuttle's computer system.

The connector and the external wiring harness were removed and sent to NASA's Marshall Space Flight Center in Huntsville, Ala., for testing. A replacement connector, featuring a harness that is soldered to the feed-through connector, is being installed this week and next.

At Marshall, initial tests subjecting the original flight hardware to ultra-cold cryogenic conditions resulted in "power fluctuations" in one of the ECO circuits, a spokesman said today, which "lends credibility" to the theory that intermittent, temperature-induced contact between pins and sockets in the connector hardware "really is the issue we've got."

The test signature was not identical to the the open circuits experienced during the launch scrubs and subsequent tanking test. But troubleshooting is far from complete, including cryogenic tests to verify the integrity of the new soldered connector design.

Space station flight controllers, meanwhile, are gearing up for a spacewalk by Expedition 16 commander Peggy Whitson and Dan Tani around Jan. 30 to replace a solar array positioning motor that failed late last year. NASA also plans a senior-management shuttle flight readiness review that same day.

If all goes well, Atlantis' countdown will begin the afternoon of Feb. 4, the same day NASA unveils the Bush administration's budget for the civilian space agency. The Progress supply ship is scheduled for launch at 8:03 a.m. on Feb. 5 from the Baikonur Cosmodrome in Kazakhstan with docking on tap at 9:34 a.m. on Feb. 7, about five hours before Atlantis' scheduled launch.

Here is an abbreviated shuttle flight plan based on a launch at 2:47 p.m. on Feb. 7. The actual launch time will will be updated based on tracking of the international space station, but these times are believed to be "in the ballpark" for planning purposes (in EST and mission elapsed time; a detailed flight plan is available on the CBS News STS-122 Quick-Look page):

DATE/EST.......DD...HH...MM...EVENT

02/07/08
Thu 02:47 PM...00...00...00...STS-122 launch
Thu 08:47 PM...00...06...00...Crew sleep begins

02/08/08
Fri 04:47 AM...00...14...00...Crew wakeup
Fri 09:12 AM...00...18...25...Heat shield inspection begins
Fri 03:07 PM...01...00...20...Heat shield inspection concludes
Fri 08:47 PM...01...06...00...Crew sleep begins

02/09/08
Sat 04:47 AM...01...14...00...STS crew wakeup
Sat 11:34 AM...01...20...47...Atlantis docks with space station
Sat 08:47 PM...02...06...00...STS crew sleep begin

02/10/08
Sun 04:47 AM...02...14...00...STS/ISS crew wakeup
Sun 09:37 AM...02...18...50...EVA-1: Spacewalk begins
Sun 03:47 PM...03...01...00...Columbus bolted to station
Sun 04:07 PM...03...01...20...EVA-1: Airlock repressurization
Sun 08:47 PM...03...06...00...STS/ISS crew sleep begins

02/11/08
Mon 04:47 AM...03...14...00...STS/ISS crew wakeup
Mon 03:22 PM...04...00...35...Columbus module ingress
Mon 08:47 PM...04...06...00...STS crew sleep begins

02/12/08
Tue 04:47 AM...04...14...00...STS/ISS crew wakeup
Tue 09:37 AM...04...18...50...EVA-2: Spacewalk begins
Tue 11:47 AM...04...21...00...EVA-2: Nitrogen tank installation
Tue 04:07 PM...05...01...20...EVA-2: Airlock repressurization
Tue 07:47 PM...05...05...00...STS crew sleep begins

02/13/08
Wed 03:47 AM...05...13...00...STS/ISS crew wakeup
Wed 07:47 AM...05...17...00...Shuttle crew off duty
Wed 07:47 PM...06...05...00...STS crew sleep begins

02/14/08
Thu 03:47 AM...06...13...00...STS/ISS crew wakeup
Thu 08:37 AM...06...17...50...EVA-3: Spacewalk begins
Thu 08:57 AM...06...18...10...EVA-3: External experiments moved to Columbus
Thu 03:07 PM...07...00...20...EVA-3: Airlock repressurization
Thu 06:47 PM...07...04...00...STS crew sleep begins

02/15/08
Fri 02:47 AM...07...12...00...STS/ISS crew wakeup
Fri 09:47 AM...07...19...00...Joint crew news conference
Fri 02:17 PM...07...23...30...Farewell ceremony
Fri 02:32 PM...07...23...45...Hatches closed
Fri 06:47 PM...08...04...00...STS crew sleep begins

02/16/08
Sat 02:47 AM...08...12...00...STS/ISS crew wakeup
Sat 06:37 AM...08...15...50...UNDOCKING
Sat 10:27 AM...08...19...40...Heat shield inspection begins
Sat 02:52 PM...09...00...05...Heat shield inspection concludes
Sat 06:17 PM...09...03...30...STS crew sleep begins

02/17/08
Sun 02:17 AM...09...11...30...Crew wakeup
Sun 04:52 AM...09...14...05...Cabin stow
Sun 06:17 AM...09...15...30...Flight control system checkout
Sun 02:17 PM...09...23...30...Crew off duty
Sun 06:17 PM...10...03...30...Crew sleep begins

02/18/08
Mon 02:17 AM...10...11...30...Crew wakeup
Mon 09:44 AM...10...18...57...Deorbit ignition
Mon 10:45 AM...10...19...58...Landing

3:00 PM, 1/8/08, Update: Connector upgrade ready for installation; lab testing continues

An upgraded wiring connector will be ready for installation on the shuttle Atlantis' external tank this week in a bid to eliminate the vexing open circuits that grounded the orbiter twice in December. The upgrade is based on a design change implemented by tank-builder Lockheed Martin in the company's Centaur upper stages in the 1990s, a fix that eliminated similar problems with unmanned Atlas- and Titan-Centaur rockets.

The Centaur veterans called in to modify the shuttle's engine cutoff - ECO - sensor pass-through connector said Monday they were optimistic parallel testing at the Marshall Space Flight Center in Huntsville, Ala., will show the shuttle upgrade will resolve NASA's problem once and for all.

"From my point of view, I certainly appreciated the opportunity to come over and help," said James Whelan, electrical and avionics manager for United Launch Alliance's Atlas operations at the Cape Canaveral Air Force Station. "We are hopeful this is going to help solve this mystery.

"It's pretty cool we get to work across a different group of individuals, across a different group of companies. We came together in a fairly short period of time across a holiday and came up with a design solution and implemented something we're hopeful will solve this problem. For me, it's been a good experience."

Asked how many hours he put in modifying the shuttle connectors with soldered pins and sockets, Kenny Reaume, a senior electrical systems engineer with Lockheed Martin, joked that "I can't tell you. My boss would fire me."

NASA attempted to launch Atlantis on a long-awaited mission to deliver Europe's Columbus research module to the international space station on Dec. 6. But the countdown was called off during fueling when tests indicated intermittent open circuits in the ECO sensor circuitry. Similar problems cropped up during a second launch attempt Dec. 9.

Launch then was retargeted for no earlier than Jan. 10, a buffer intended primarily to ensure holiday time off for the shuttle launch team and to give engineers more time to assess the problem. Program managers later moved the target date to no earlier than Jan. 24, saying actual work to fix the connector, install it and re-apply foam insulation likely would push the flight into early February.

As of this writing, that remains the expectation, with insiders saying the flight could slip to after launch of a Russian Progress supply ship. That flight currently is scheduled for takeoff Feb. 7, but the Russians may be able to move launch up a few days depending on how the repair work plays out.

In the meantime, space station flight controllers are making plans for a spacewalk by Expedition 16 commander Peggy Whitson and Dan Tani toward the end of the month to replace a suspect solar array positioning motor. That work is unrelated to on-going analysis of problems with a massive rotary joint on the right side of the station's main power truss that is needed to turn outboard arrays to track the sun.

Engineers do not yet understand what caused unusual erosion inside the starboard solar alpha rotary joint and there are no immediate plans to attempt any sort of repairs. The spacewalk later this month will be devoted to installing a new motor used to change the pitch of one set of right-side arrays.

The four ECO sensors at the base of the Atlantis' hydrogen tank are part of a backup system intended to make sure the shuttle's main engines don't suck a tank dry after some other problem - a leak, for example, or an improper hydrogen-oxygen mixture ratio - used up propellant at faster than normal rates. An engine running out of hydrogen during normal operation likely would suffer a catastrophic failure.

The 10 wires that carry signals from all four ECO sensors and a 5 percent sensor pass through the same connector in the wall of the external tank. The three-part 37-pin connector (27 pins are not used) features a pass-through fitting with gold-plated male pins on both sides.

Wires from the sensors inside the tank terminate in a female connector inside the tank that is plugged into the male pins of the pass-through. Those pins are imbedded in a glass matrix. A similar female socket plugs into the pass-through on the outside of the tank where the pins are mounted in a Teflon insert.

Based on data collected during a fueling test Dec. 18, engineers believe the problem involves circuit-breaking gaps in pins and sockets on the external side of the feed-through connector when the system is chilled to ultra-low temperatures. They believe the sensors themselves are healthy.

"In my experience, very, very cold (temperature) does weird things to metal," Whelan said. "In some cases it shrinks, then it grows and then it changes. It's always interesting working with cryogenics, that's for sure."

The feed-through plate with the external connector still attached was removed and shipped to the Marshall Space Flight Center for additional testing at cryogenic temperatures. Engineers are hopeful they will see the same sort of continuity problems that cropped up during last month's launch attempts. If so, managers will have higher confidence the issue is, in fact, understood.

Back at the Kennedy Space Center, meanwhile, NASA assembled a team of Lockheed Martin and United Launch Alliance engineers to modify replacement connectors, soldering the external wires to the pins in the feed-through connector. The team modified one set of hardware for eventual installation on Atlantis' external tank (ET-125) and two more sets were sent to Marshall for qualification testing at liquid hydrogen temperatures.

Whelan said in the 1990s, Lockheed Martin ran into problems with its Centaur second stage propellant utilization system. The hydrogen-fueled Centaur stage was designed for use with unmanned Atlas and Titan rocket systems.

"We had a data signature on both a Titan-Centaur and an Atlas-Centaur vehicle that led us to believe that we were seeing some intermittent contact or some loss of continuity in our circuitry in our propellant utilization system," Whelan said. "We found a solution which essentially soldered the sockets to the pins of our interface connector on our tank.

Lockheed Martin engineers decided not to modify the connectors inside the tank. Only the external side of the connector was soldered, the same modification approved for the shuttle hardware.

"We've got all new hardware," Reaume said. "We're actually building these sub assemblies right here at KSC in a lab. We have a crew of folks from New Orleans, Lockheed Martin/Michoud, and we have James Whelan and two of his technicians that did the same repair on Atlas. We're working side by side building these sub assemblies up. We have connector experts and harness-build experts here, technicians that have done this probably close to 30 years combined with all these folks. They're all senior-most people, working side by side with Mr. Whelan and his folks, building up the wires and preparing them.

"We actually have four pieces in work at one time," he said. "We just completed two. Actually, the first flight unit that's going to go up to ET-125 is about 99 percent complete, we're just doing some touch ups on it right now, some final electrical re-test. We have two qualification units that are going to go up to Marshall Space Flight Center for some qualification testing. And we had one other test unit that went up to Marshall Space Flight Center as well."

Flight units will be leak tested under flight pressures and subjected to a 50-power microscopic examination before installation. For Atlantis, the flight hardware will be installed before testing at Marshall is complete. That testing will subject the two qualification units to a minimum of five cryogenic cycles each, according to Steve Swichkow, branch chief of NASA's external tank/solid rocket booster electrical engineering group at KSC.

The new connector hardware is built up by passing the incoming wires "all the way through the connector," Reaume said. "After we slide the wire through, we actually crimp the little sockets on. From there, they're actually soldered to the bulkhead connector. When we reassemble this connector and actually put it into a mated position, it's a lot like ... an air hose. It has the coupling ring that you pull back and you engage and it's got the little ball locks that actually lock, you slide the little coupling ring forward and it locks the hose into place. If you can picture that, it's exactly the same concept. You slide it in, you engage it, the coupling ring slides forward and it locks it into place."

Engineers plan to begin installing the upgraded connector on Atlantis' tank Thursday. Once it is in place, foam insulation will be reapplied. The shuttle's eventual launch date will depend, in part, on how long it takes the insulation to "cure," a process that can be affected by humidity, temperature and other weather issues. One internal estimate shows Atlantis being ready for launch 25 days after the connector hardware installation begins. But given the many variables involved, engineers say it's too soon to say when the shuttle might be ready to fly.

7:45 PM, 1/3/08, Update: Shuttle launch no earlier than Jan. 24 as NASA pursues parallel ECO testing/hardware replacement

NASA managers today agreed to press ahead with work to replace suspect engine cutoff - ECO - sensor connectors on the shuttle Atlantis' external tank on the assumption parallel laboratory testing will confirm the root cause of open circuits that derailed two December launch tries. Assuming the replacement work goes smoothly, the weather cooperates and the lab testing goes as engineers hope it will, Atlantis could be ready for a third launch try by Jan. 24.

But John Shannon, deputy manager of the shuttle program at the Johnson Space Center in Houston, told reporters Jan. 24 is little more than a best-case crew training and planning target and that Feb. 2 is a more realistic launch date given the work required.

And that assumes everything goes smoothly. If the lab testing at the Marshall Space Flight Center in Huntsville, Ala., does not replicate the December trouble, i.e., if the removed connector hardware works normally under super-cold cryogenic conditions, another on-pad fueling test might be required to collect additional data. In that case, launch could slip to around Feb. 7 at the earliest.

"There's no way we're going to be earlier than Jan. 24," Shannon said. "I would say it is a stretch to think we would make the 24th, that would require the weather to cooperate out at the Kennedy Space Center, it would require no hitches in any of the testing or re-application of (foam insulation on the tank around the connector).

"But I asked the team to go ahead and protect that date as the earliest date that we could possibly go," he said. "I think it is much more likely that we'll be ready to go somewhere in the Feb. 2 to Feb. 7 timeframe, given we don't have any additional findings as we go through our testing."

A wild card in NASA's planning is the scheduled Feb. 7 launch of a Russian Progress supply ship from the Baikonur Cosmodrome in Kazakhstan. Joint U.S.-Russian space station flight rules forbid a Progress docking during a shuttle visit. If the Russians stick with Feb. 7, Atlantis would have to take off by Jan. 27 or the flight would slip to around Feb. 9 to get the Progress docked before the shuttle arrives.

A more realistic launch target is expected in a week to 10 days.

Atlantis was grounded last month when intermittent failures of ECO sensors at the base of the hydrogen tank occurred during fueling and later, draining. A fifth sensor, which indicates when the tank is 5 percent full, also malfunctioned when the tank was drained.

The ECO sensors are part of a backup system intended to make sure the shuttle's main engines don't inadvertently drain a tank dry after some other problem - a leak, for example, or an improper hydrogen-oxygen mixture ratio - used up propellant at faster than normal rates. An engine running out of hydrogen during normal operation likely would suffer a catastrophic failure.

The wires that carry signals from all four ECO sensors and the 5 percent sensor pass through the same connector in the wall of the external tank. The three-part connector features a pass-through fitting with male pins, embedded in glass, on both sides. Wires from the sensors inside the tank terminate in a female connector inside the tank that is plugged into the male pins of the pass-through. A similar female socket plugs into the pass-through on the outside of the tank.

Based on data collected during a fueling test Dec. 18, engineers believe the problem involves gaps in pins and sockets on the external side of the feed-through connector when the system is chilled to ultra-low temperatures. They believe the sensors themselves are healthy.

Engineers have now removed the pass-through pin plate and the external connector, keeping the actual pin-socket interface intact for testing. The internal connector, which cannot be replaced at the pad, was inspected and no obvious problems were seen.

The feed-through plate with the external connector still attached has been shipped to the Marshall Space Flight Center for additional testing at cryogenic temperatures. Engineers are hopeful they will see the same sort of continuity problems that cropped up during last month's launch tries. If so, managers will have higher confidence the issue is, in fact, understood.

"It's a difficult problem," Shannon said. "I'm not making excuses here, but at liquid hydrogen temperatures is the only time it shows up so you have to set up a test that uses liquid hydrogen. We're very interested (in the results), this is the first time we've removed (this) hardware from a vehicle and had the opportunity to test it without disturbing it before hand. So it will be interesting to find out."

While the testing is going on at Marshall, engineers at Kennedy will replace the pass-through plate and external connector with hardware featuring soldered pins and sockets. A similar design was successfully implemented in the 1990s by Lockheed Martin to address problems with hydrogen-fueled Centaur rocket stages.

Along with soldered pins and sockets, the replacement hardware will feature what amounts to additional slack to permit temperature-induced motion in the wiring that otherwise might put stress on the connector. The modifications should eliminate any possible electrical continuity problems in the external connector hardware.

"All of those changes, it's fairly simple, it's a fairly elegant change and we feel very confident that if the problem is where we think it is, between the external connector and the feed through, that this will solve that," Shannon said. "Now, if you look at the schedule, we're going to have new external connectors and feed-through assemblies at KSC this weekend and we're going to proceed with installing that on external tank Number 125, which is the one Atlantis is currently mated to. We expect that work to be done by next Thursday.

"We're going to do that change and it will occur before we're finished with all our testing out at Marshall Space Flight Center. We had some discussions on that. We are taking some schedule risk on the program side that if we go through our testing at Marshall and determine there's a new failure mode or something we didn't expect or we learn something new, we might have to go and take that back out. But we feel very confident we are addressing the real problem."

NASA originally planned to launch the shuttle Endeavour on Feb. 14. But the Atlantis delay will force a corresponding slip for Endeavour. Shannon said NASA typically requires five weeks between launches to complete a given mission and provide time to evaluate in-flight problems before launching the next flight.

Shannon said NASA managers have not yet assessed how subsequent flights might be affected.

6:00 PM, 12/27/07, Update: NASA orders external ECO sensor plug/socket replacement with soldered components; launch date under review

NASA managers today cleared engineers to remove the external components of a suspect feed-through connector built into the wall of the shuttle Atlantis' external tank in a bid to fix intermittent electrical problems with low-level engine cutoff - ECO - sensors that derailed launch attempts Dec. 6 and 9. The external fittings will be replaced with soldered pins and sockets like those developed and successfully flown by tank builder Lockheed Martin for its Centaur rocket stages.

Shuttle Program Manager Wayne Hale said today the work likely will delay Atlantis' launch "a few days to a couple of weeks" beyond the previous Jan. 10 target. But that "no-earlier-than" date was little more than a placeholder intended to ensure the launch team enjoyed a few days off over the Christmas holiday. As such, it was not based on any actual repair schedule.

NASA has now settled on a course of action, but Hale said today he was not ready to discuss when Atlantis might be ready for a third launch try. During an afternoon teleconference, he told reporters "I'm not going to make a launch date announcement ... because we're in the middle of troubleshooting and repair. Until that gets a little bit further along, I actually have no valid dates to give you."

"To avoid what I think would be a totally misleading headline along the lines of 'NASA delays the space shuttle again,' we're just not going to give you a launch date because that, in fact, would not be accurate," he said.

But sources familiar with the discussion said the feed-through connector replacement and subsequent testing could delay launch to the last week in January when all is said and done, and that assumes the work goes smoothly.

Atlantis was grounded Dec. 6 and 9 when intermittent failures of ECO sensors at the base of the hydrogen tank occurred during fueling and later, draining. A fifth sensor, which indicates when the tank is 5 percent full, also malfunctioned when the tank was drained.

The ECO sensors are part of a backup system intended to make sure the shuttle's main engines don't inadvertently drain a tank dry after some other problem - a leak, for example, or an improper hydrogen-oxygen mixture ratio - used up propellant at faster than normal rates. An engine running out of hydrogen during normal operation likely would suffer a catastrophic failure.

The wires that carry signals from all four ECO sensors and the 5 percent sensor pass through the same connector in the wall of the external tank. The three-part connector features a pass-through fitting with male pins, embedded in glass, on both sides. Wires from the sensors inside the tank terminate in a female connector inside the tank that is plugged into the male pins of the pass-through. A similar female socket plugs into the pass-through on the outside of the tank.

The central feed-through fitting features 37 pins on each side, only 10 of which are actually used. Each pin is roughly two-and-a-half inches long and one-sixteenth of an inch in diameter. The 37-socket connectors that attach to each side of the central feed-through are a little more than an inch across, Hale said.

Based on data collected during a fueling test Dec. 18, engineers believe the problem involves gaps in pins and sockets on the external side of the feed-through connector when the system is chilled to ultra-low temperatures. They believe the sensors themselves are healthy and that only two circuits are actually experiencing problems: ECO sensors 1 and 3.

"We have allowed the team that did the troubleshooting to very thoroughly go through all of that data," Hale said today. "They have told us they are sure that the problems that we're seeing reside in that series of connectors (on the external side of the interface). Where exactly in that series of connectors is a little bit open to interpretation.

"We would like to get the whole thing out and send it to a laboratory for bench analysis. Unfortunately, as we discussed today, that's probably not a really good option. So what we decided to do today is to tell the team to take the next step and remove the pass-through plug and the external connector and some length of the wiring on the outside as a unit and send that back to the lab."

The removed components will be bench tested under cryogenic conditions in an attempt to duplicate the observed failure mode. In the meantime, replacement hardware featuring soldered pins and sockets will be installed on the tank at the launch pad.

The internal connector that plugs into the pass-through pins from the inside of the tank does not have enough slack in the wires leading to the ECO sensors to permit the internal connector's removal. It will be visually inspected, however, and possibly X-rayed to check its integrity. But Hale agreed that NASA will face the possibility that the repairs ordered today might not fix the problem.

"It is a possibility that the internal connector is involved," he said. "However, all the physics-based discussion of the kinds of things that can happen point to something happening on the external connector. The Centaur problem was a problem with the external connector. And so while it's not a slam dunk, guaranteed situation, the preponderance of evidence indicates that the external connector is the problem."

Engineers are keeping their fingers crossed because "getting the internal connector out is much more invasive and there's much greater risk of flight hardware damage because you have to actually go into the hydrogen tank to get to the internal connector to replace it," Hale said. "We can pull it out just far enough to do a visual inspection, perhaps take some X-rays, but you cannot replace that connector from the outside of the tank. To get into the hydrogen tank, then you have to roll back to the VAB (Vehicle Assembly Building) and do all the work that's involved there.

"Since the preponderance of evidence to a very high degree point to the external connector - we can get to that, we know how to fix it, that's been our experience with our sister program - that's where we're going to concentrate our efforts. Of course, if we're unsuccessful we will come back and look at the internal connector again."

5:30 PM, 12/21/07, Update: Hale hopeful near-term fix possible for ECO sensors; engineers tentatively cleared to remove suspect connector, plug

Engineers have been provisionally cleared to remove a suspect feed-through plug and an external connector from the shuttle Atlantis' external fuel tank for laboratory testing and a possible fix to eliminate intermittent electrical glitches with low-level engine-cutoff sensors.

In an interview today with CBS News, shuttle Program Manager Wayne Hale said no final decisions have been made, but one leading candidate for a near-term repair is to possibly solder the external socket to the male pins in the pass-through connector to eliminate any open circuits in that part of the system when it is chilled to cryogenic temperatuures.

This scenario assumes the internal connector is sound and is not contributing to the problem. The internal connector cannot be modified unless repair crews enter the external tank, work that likely would require a roll back to the Vehicle Assembly Building.

"The leading contender today is we will, starting next week, pull the through plug with the external connector, all in one piece, off (the tank), clip the wires and wire harness and send that whole assembly off to the lab for teardown and evaluation," he said.

"Then in parallel, we've got a (qualification) process that's going through a solder of the wires directly to the male pins of the pass through. And of course, you close all that out, splice your wires into the wire harness and plug it back in."

But that is simply one option under consideration. How the agency will actually proceed - and what that might mean in terms of an eventual launch date - will depend on what engineers find when they remove and examine the hardware.

The current "no-earlier-than" launch date is Jan. 10, but that target was announced before engineers had a good idea of what might be needed to fix the problem.

Of seven options presented to shuttle managers Wednesday, only two - simply replacing the external connector or swapping out the connector and the pass-through plug - lead to launch attempts in early to mid January. Replacing the external connector with a soldered pin-and-plug arrangement likely would result in additional delay.

But again, it's not yet clear how NASA will proceed.

Going into the weekend before the Christmas holiday, Hale said he had given the team "kind of a two-part guidance. If they can come to a consensus that we don't have to go into the tank taking these pieces out, then I basically told them to go ahead and do that. If they can't get to that and they need to go into the tank, then we need to have a management review before they do that because ... getting into a tank includes a fair amount of technical risk. So they're off working on those two things."

Engineers also are reviewing low-level engine cutoff - ECO - sensor problems in other rocket systems to learn about other possible approaches to the problem.

Lockheed Martin's Atlas-Centaur rockets "had some problems, Centaur (second stage) did, back in the early '90s and they have gone to not using the kind of pin-and-socket connectors that we use and actually soldering the wires through this kind of system," Hale said. "And then I've got a huge dump here from the NESC (NASA Engineering and Safety Center) on every other anomaly report they could find in the history of mankind, almost, on connector failures, particularly in the cryogenic experience.

"We've got problem reports with connectors from Los Alamos National Labs, the Ames Research Center, some ELV (unmanned rocket) problems, just all over the place, some of which sound like ours, some of which don't. So we're using that in our team to evaluate these things and say what can we learn from this history that's out there? So, that's going into the team that's working very hard to come up with a change."

Atlantis was grounded Dec. 6 and 9 when intermittent failures of ECO sensors at the base of the hydrogen tank occurred during fueling and later, draining. A fifth sensor, which indicates when the tank is 5 percent full, also malfunctioned when the tank was drained.

The wires that carry signals from all five sensors pass through the same connector in the wall of the external tank. The three-part connector features a pass-through fitting with male pins, embedded in glass, on both sides. Wires from the sensors inside the tank terminate in a female connector inside the tank that is plugged into the male pins of the pass-through. A similar female socket plugs into the pass-through on the outside of the tank.

Based on data collected during a fueling test Dec. 18, engineers believe the problem involves gaps in the external part of the connector that are occurring when the system is chilled to ultra-low temperatures. They believe the sensors themselves are healthy and that only two circuits are actually experiencing problems: ECO sensors 1 and 3.

"The feed-through plug is a male-male plug," Hale said. "If you think about it, each of the pins goes through this vitreous glass (in the wall of the tank) and then the connectors the wire harnesses terminate in are the female sockets.

"The guys reported yesterday ... they came back and said we're pretty sure that the ECO sensor 1 (problem) was on the outside but ECO sensor 3, we're kind of indeterminate on. I haven't heard the results. It would really be nice if we could say with a high degree of confidence this is on the outside."

If the problem is, in fact, in the plug or external connector, repairs could be made at the launch pad. But if the problem involves the internal connector, engineers likely would have to go inside the tank and that, almost certainly, would require a rollback to the Vehicle Assembly Building.

"If we go inside, that's going to complicate our lives," Hale said. "You've got to go into the tank and that probably is going to require a rollback.

"But there are a multiplicity of options. The thing I've got to do as a manager is kind of sit on my hands for a couple of days, let the technical guys slug it out and come forward with a recommendation and not try to keep pulling this plan up by the roots to see how it's doing."

The goal of Atlantis' flight is to deliver the European Space Agency's Columbus research module to the international space station. But problems with the systems used to keep the station's solar arrays properly pointed at the sun could force station planners to schedule a spacewalk to swap out a so-called beta gimbal assembly motor.

Depending on when such a spacewalk might be scheduled, Atlantis could face additional delays not related to the ECO sensor work. Asked if NASA might take advantage of any such delay to implement a more extensive ECO sensor fix, Hale said the near-term goal is to get Atlantis ready to fly as soon as possible.

"I don't think that's going to factor at all," Hale said. "My goal is to get back to a highly reliable system as soon as we can to be ready to fly as soon as we practically can and then if station has other considerations, then we'll talked about what makes sense. And I know they're working their problems."

But engineers at the Marshall Space Flight Center in Huntsville, Ala., are assessing potential long-term fixes that might be implemented several flights downstream. But for the two tanks at the Kennedy Space Center - Atlantis' and a tank scheduled for launch with the shuttle Endeavour in February - some sort of interim fix appears more likely.

"We've got the short-term team, which is looking on the near-term flights, the two tanks effectively that we have at the Kennedy Space Center, what are we going to do near term in which you would go off and do some kind of quick change that would mitigate if not everything, most things.

"Then we've put together what we call the long-term team under one of the chief engineer people at Marshall Space Flight Center, who's looking at a three- to four-month longer term investigation and come back with what we should do for the long term. I'd like to eliminate it as an issue."

As for whether NASA must find and address the "root cause" of the problem before Atlantis flies, Hale said "it depends on what our fix is."

"If you go to a completely different class of fix, which is why I think everybody is so enamored of the solder (technique), then you could probably say you don't need to go to root cause, I just need to know where the problem was occurring and we took it out.

"If we find out, for example, soldering doesn't work - and there's some discussion about what happens to solder joints in cryogenic temperatures, do they break or degrade - if that doesn't work and we need to go back with a plug-type socket connector again, but a different strength or different assembly method, something of that nature, then you really need to go to root cause. And that takes a bit of time."

06:30 PM, 12/19/07, Update: NASA managers assess ECO sensor options; additional review 12/27

NASA managers today reviewed options for fixing suspect low-level engine cutoff - ECO - sensors in the shuttle Atlantis' fuel tank. No final decisions were made and potential launch dates were not discussed. But shuttle Program Manager Wayne Hale, officials said, ruled out any discussion of launching Atlantis as is and engineers were cleared to begin preparations for removing foam insulation around a suspect "feed-through" electrical connector that passes sensor data into and out of the huge tank.

ECO circuit malfunctions blocked two attempts to launch Atlantis on a long-awaited space station assembly mission. During a fueling test Tuesday, test instrumentation spliced into the ECO sensor circuitry traced the problem to the three-part feed-through connector where wiring from the four ECO sensors and a so-called 5-percent sensor passes through the wall of the tank.

While the exact location of the fault is still under assessment, engineers are hopeful additional testing and data analysis will show the problem is in the external part of the feed-through connector, the plug on the outside of the tank that is relatively easy to access at the launch pad.

If so, that part of the connector could be replaced. If subsequent testing in a laboratory setting under ultra-low temperature cryogenic conditions duplicates the previously seen failures, NASA could press ahead for a third attempt to get the shuttle off the ground as early as mid January.

The current "no-earlier-than" launch date is Jan. 10, but that target was announced before engineers had a good idea of what might be needed to fix the problem. It's not yet clear whether Atlantis can be ready by then even if the problem is, in fact, in the external part of the connector.

"That would obviously be the best scenario," said a NASA official. "If it's that, if you could somehow guarantee that's what it is, you don't have to be invasive to the tank. ... There's some optimism it's in the external part of the connector."

But if it turns out the problem is in the internal parts of the connector hardware, engineers would have to remove foam from the bottom of the tank, open an access port and work inside the structure. Such invasive work likely would require a rollback to the Vehicle Assembly Building, delaying Atlantis' flight well beyond Jan. 10.

Sources said some engineers believe it makes more sense to accept a longer launch delay now to implement a permanent fix, replacing the entire connector with a redesign that features soldered pins to eliminate temperature-induced open circuits once and for all.

But any such redesign would face extensive testing above and beyond the work needed to fix Atlantis' tank and launch likely would slip into February.

Another school of thought says it makes more sense to attempt a connector fix that would get Atlantis safely off the pad as soon as possible and to implement a long-term fix in parallel.

"There's a strong push to fix this problem on the pad and get the launch off," said one senior manager familiar with the discussions.

The downside to that approach, he said, is the possibility the data indicating the fault lies in the external part of the connector is incorrect or is being misinterpreted. In that case, additional problems could develop during the next launch attempt, forcing NASA to change its launch commit criteria or order a lengthy stand down and roll back for a more extensive repair.

A wild card in the discussion is what to do about fixing a recent problem with a space station solar array that is limiting the power available to the outpost. It appears a spacewalk by the station crew would be needed to replace a so-called beta gimbal assembly motor before Atlantis could fly regardless of work to fix the ECO sensors. While the station repair work could be added to the Atlantis mission, it would require major replanning.

As of this writing, no decisions have been made on how to proceed with either problem.

In the near term, Hale approved plans to begin preparations for removing foam from around the connector and to continue data analysis and engineering reviews. Another meeting to re-assess preparations and discuss repair options is planned for Dec. 27.

The ECO sensors are part of a backup system intended to make sure the shuttle's main engines don't inadvertently drain a tank dry after some other problem - a leak, for example, or an improper hydrogen-oxygen mixture ratio - used up propellant at faster than normal rates. An engine running out of hydrogen during normal operation likely would suffer a catastrophic failure.

NASA's launch commit criteria call for three of the four ECO sensors to be working properly for a launch to proceed.

During fueling for a Dec. 6 launch try, ECO sensors 3 and 4 "failed wet" about 35 minutes after they were submerged in liquid hydrogen. After the launch was called off, another sensor that shows when the tank is 5 percent full failed wet. After the tank was drained, ECO sensor No. 1 failed wet as well.

During fueling for a second launch try Dec. 9, ECO sensor No. 3 failed wet 24 minutes after all four were submerged. In both cases, the sensors returned to normal operation after the tank was drained and temperatures rose.

During Tuesday's tanking test, sensors 2 and 3 showed open circuit failure indications for a few seconds before returning to normal operation. Sensor 1 failed shortly thereafter and stayed that way for the duration of the test. Sensor 2 worked properly throughout the tanking test but sensor 3 failed several hours after recovering from its initial open circuit indication.

Hale said Tuesday the time domain reflectometry instrumentation used during the fueling test exonerated the sensors themselves. The data indicate the only sensor circuits with real problems are ECO 1 and 3. The intermittent glitches with sensors 2 and 4 are believed to be related to the pass-through connector problem that has affected sensors 1 and 3.

6:00 PM, 12/18/07, Update:Sensor problem tracked to external tank wiring connector; corrective actions, impact on launch date not yet known

Precisely timing how electrical pulses moved back and forth through suspect engine cutoff sensor wiring during a fueling test today indicates intermittent open circuits that grounded the shuttle Atlantis on Dec. 6 and 9 were caused by problems in a critical-three part "feed-through" connector. The connector carries sensor data through the wall of the ship's external fuel tank.

While engineers do not yet know what will be required to fix the problem - or whether Atlantis can meet a no-earlier-than Jan. 10 launch date - shuttle Program Manager Wayne Hale said he was relieved today's tanking test exonerated the sensors themselves and isolated the problem to an area that is accessible at the launch pad.

"Exactly what we've got to do and where in this three-part connector we have to do it is a little bit of work ahead of us," he said. "I'm just pleased as punch we know it's in the connector and not some other place in this 100 feet or so of wiring and sensors and electronic boxes (that were in question) so we know what area to concentrate our efforts."

During fueling for a Dec. 6 launch try, engine cutoff - ECO - sensors Nos. 3 and 4 "failed wet" about 35 minutes after they were submerged in liquid hydrogen. After the launch was called off, another sensor that shows when the tank is 5 percent full failed wet. After the tank was drained, ECO sensor No. 1 failed wet as well.

During fueling for a second launch try Dec. 9, ECO sensor No. 3 failed wet 24 minutes after the others were submerged. In both cases, the sensors returned to normal operation after the tank was drained and temperatures rose.

During today's tanking test, sensors 2 and 3 showed open circuit failure indications for a few seconds before returning to normal operation. Sensor 1 failed shortly thereafter and stayed that way for the duration of the test. Sensor 2 worked properly throughout the tanking test but sensor 3 failed several hours after recovering from its initial open circuit indication.

The wiring to all four ECO sensors, as well as the 5 percent level sensor, pass through the same feed-through connector.

"Today we had problems on three of those sensors and we captured the data," Hale said. "And the data is indicating we have a problem at what we call the feed-through connector that leads the wires from the inside of the liquid hydrogen tank in the cryogenic fluid to the exterior of the tank. That's a multi-part connector and our time domain reflectometry instrumentation has indicated that is where our open circuits are occurring at these very cold temperatures.

"The team is looking at all of this data, all the recorded voltages, this TDR instrumentation, there is literally gigabytes worth of data that was collected today. They'll be going over this data very carefully for the next few days, trying to make sure they properly interpret the results.ÊThe preliminary indication is we have a problem at this connector."

Engineers plan to brief shuttle managers Wednesday on details of the tanking test, what the TDR data indicate and what repair options might be feasible.

"I do not have any information about a launch date today," Hale said. "Frankly, we are still in the midst of troubleshooting. ... Where the troubleshooting and replacement and repair work leads us will determine what the launch date's going to be. We are not going to be driven by schedule on this one. We need to get to the bottom of this, fix it and make sure it's fixed once and for all and then we can fly safely through the rest of the program, at least in this area."

The connector in question can be accessed at the launch pad but how much time it might take to replace suspect components will depend on whether the fault is found to be inside or outside the tank.

"Some timelines have been developed to change out those parts that can be reached from the outside, and they are on the order of a week to 10 days kind of work," Hale said. "However, the part that's difficult to get to is the socket connector on the inside of the tank and that would be more invasive. You would have to go inside the tank through the manhole cover we've got at the bottom or some other access point and that obviously would be a longer-term operation."

No additional tanking tests are planned in the near term, although engineers are subjecting test equipment to cryogenic conditions in the laboratory to learn more about how the connector functions when it is chilled to ultra-low temperatures.

12:30 PM, 12/18/07, Update: Initial sensor troubleshooting work complete; engineers ready to drain tank

Engineers operating test equipment inside the shuttle Atlantis' mobile launch platform completed a battery of tests today in an attempt to locate the source of intermittent electrical problems with critical engine cutoff - ECO - sensors in the base of the ship's external fuel tank.

After the tank was loaded with rocket fuel early today, the troubleshooting team went inside the MLP at launch complex 39A to operate sophisticated diagnostic equipment that had been spliced into the ECO sensor circuitry. Using a technique known as time domain reflectometry, signals sent into the circuitry can be used to precisely locate the source of any problems.

Additional data collection is planned while the tank is drained to monitor the behavior of the sensors as they warm up.

Assuming one or more problem areas are identified after data analysis, and assuming repairs can be made at the launch pad, NASA hopes to launch Atlantis on a space station assembly mission by around Jan. 10.

During fueling for a Dec. 6 launch try, ECO sensors Nos. 3 and 4 "failed wet" about 35 minutes after they were submerged in liquid hydrogen. After the launch was called off, another sensor that shows when the tank is 5 percent full failed wet. After the tank was drained, ECO sensor No. 1 failed wet.

During fueling for a second launch try Dec. 9, ECO sensor No. 3 failed wet 24 minutes after the others were submerged. In both cases, the sensors returned to normal operation after the tank was drained and temperatures rose.

During today's tanking test, sensor No. 1 failed while sensors 2 and 3 suffered intermittent failures. Sensor 4 operated normally. A briefing with shuttle Program Manager Wayne Hale is expected late this afternoon.

8:26 AM, 12/18/07, Update: ECO sensor 1 fails; sensors 2 and 3 show intermittent problems

An hour and a half into a shuttle fueling test, engine cutoff - ECO - sensor No. 1 has failed while sensors 2 and 3 show signs of intermittent trouble. The hard failure with sensor No. 1 was a welcome development, because it means test equipment spliced into the ECO sensor circuitry should be able to pinpoint the location of the open circuit.

Whether sensors 2 and 3 ultimately will be declared failed remains to be seen, but sensor No. 2 never acted up during two earlier launch attempts and as such, its behavior was somewhat of a surprise.

Once the external tank is full and in stable replenish mode, a team of engineers will enter the shuttle's mobile launch platform to begin a series of tests with special instrumentation in an attempt to pinpoint the source of the sensor problems.

7:30 AM, 12/18/07, Update: Shuttle fueling test begins

Engineers began pumping liquid hydrogen rocket fuel into the shuttle Atlantis' external tank today in a high-stakes test to find out what's causing intermittent problems with low-level engine cutoff - ECO - sensors that derailed two launch tries Dec. 6 and 9.

With launch now on hold until at least Jan. 10, engineers are hopeful special test equipment spliced into the ECO sensor circuitry will help pinpoint a presumed wiring or connector problem that only shows up after the system has been exposed to liquid hydrogen at minus 423 degrees Fahrenheit.

Fuel loading began with transfer line chilldown shortly after 7 a.m. Once the tank is full and in stable replenish mode, five technicians will enter the shuttle's mobile launch platform to begin a series of tests to troubleshoot the sensor problem.

The ECO sensors are part of a backup system intended to make sure the shuttle's main engines don't inadvertently suck a tank dry after some other problem - a leak, for example, or an improper hydrogen-oxygen mixture ratio - used up propellant at faster than normal rates. An engine running out of hydrogen during normal operation would have catastrophic consequences.

During fueling Dec. 6, ECO sensors Nos. 3 and 4 "failed wet" about 35 minutes after they were submerged in liquid hydrogen at minus 423 degrees Fahrenheit. After the launch was called off, another sensor that shows when the tank is 5 percent full failed wet. After the tank was drained, ECO sensor No. 1 failed wet.

During fueling Dec. 9, ECO sensor No. 3 failed wet 24 minutes after the others were submerged. In both cases, the sensors returned to normal operation after the tank was drained and temperatures rose.

Because of the timing of the malfunctions, engineers are hopeful the sensors themselves, located inside the huge external tank and not easily accessible at the launch pad, are healthy.

The problems could be due to broken or damaged wires, bent or recessed pins in critical connectors or even debris in a connector. Data collected during the tanking test today should help narrow down the location of the problem and help determine what might be needed to fix it.

5:00 PM, 12/13/07, Update: Launch no earlier than Jan. 10; station spacewalk, tanking test on tap Dec. 18

Launch of shuttle Atlantis on a critical space station assembly mission, delayed twice because of problems with troublesome low-level fuel sensors, will slip an additional week, from Jan. 2 to no earlier than Jan. 10, to give support personnel time off over the Christmas and New Year holidays, NASA managers said today.

"Moving the next launch attempt of Atlantis to Jan. 10 will allow as many people as possible to have time with family and friends at the time of year when it means the most," shuttle Program Manager Wayne Hale said in a statement late today. "A lot has been asked of them this year and a lot will be asked of them in 2008."

With test instrumentation spliced into the engine cutoff - ECO - sensor circuitry in the shuttle's aft engine compartment, engineers plan to pump supercold liquid hydrogen rocket fuel back into Atlantis' external tank Tuesday.

The goal of the test is to collect data that should help pinpoint the location of whatever problem caused multiple ECO sensors to malfunction during launch attempts Dec. 6 and 9 that grounded Atlantis and the European Space Agency's Columbus research module.

The Jan. 10 target date assumes whatever is wrong can be fixed at the launch pad without any major impact to normal processing.

The ECO sensors are part of a backup system intended to make sure the shuttle's main engines don't inadvertently suck a tank dry after some other problem - a leak, for example, or an improper hydrogen-oxygen mixture ratio - used up propellant at faster than normal rates. An engine running out of hydrogen during normal operation would have catastrophic consequences.

During fueling Dec. 6, ECO sensors Nos. 3 and 4 "failed wet" about 35 minutes after they were submerged in liquid hydrogen at minus 423 degrees Fahrenheit. After the launch was called off, another sensor that shows when the tank is 5 percent full failed wet. After the tank was drained, ECO sensor No. 1 failed wet.

During fueling Dec. 9, ECO sensor No. 3 failed wet 24 minutes after the others were submerged. In both cases, the sensors returned to normal operation after the tank was drained and temperatures rose.

Because of the timing of the malfunctions, engineers are hopeful the sensors themselves, located inside the huge external tank and not easily accessible at the launch pad, are healthy.

The problems could be due to broken or damaged wires, bent or recessed pins in critical connectors or even debris in a connector. Data collected during the tanking test Tuesday should help narrow down the location of the problem and help determine what might be needed to fix it.

If the Jan. 10 target holds up, liftoff would be scheduled for 2:26:10 a.m., setting up docking with the space station around 11:13 p.m. on Jan. 11. Three spacewalks are planned with the first two beginning around 9:15 p.m. on Jan. 12 and 14 and the third starting an hour earlier on Jan. 16. Landing back at the Kennedy Space Center would be expected around 10:24 p.m. on Jan. 20.

Depending on when Atlantis' actually flies, mission managers may extend the flight two days and add a fourth spacewalk to the mission.

While the tanking test is going on at the Kennedy Space Center in Florida on Tuesday, the crew of the international space station plans to carry out a 6.5-hour spacewalk to inspect a contaminated solar array rotary joint and another more recent power system glitch that could be the result of a micrometeoroid or debris impact.

The spacewalk, by Expedition 16 commander Peggy Whitson and flight engineer Dan Tani, is scheduled to begin at 6 a.m.

The station is equipped with two massive solar alpha rotary joints, one on each side of the lab's main power truss, designed to slowly turn outboard arrays like giant paddle wheels to keep them face on to the sun.

Each solar blanket also is equipped with a so-called beta gimbal joint to turn the arrays from side to side, like changing the pitch of a propeller, to maximize electrical output.

The port-side SARJ is operating normally as are the four beta gimbal assemblies on the four left-side solar wings. But the starboard SARJ is locked in place because of excessive vibration and recently discovered internal metallic contamination and bearing race ring damage.

In addition, one of the two beta gimbal joints on the right side is now locked in place because of circuit breaker trips last week that may have been caused by a space debris impact.

As for the starboard SARJ, engineers suspect one or more of the 12 trundle bearings that press against the 10-foot-wide race ring with 1,000 pounds of force could be causing the observed damage. Data from instrumentation shows vibrations are highest near bearing assembly No. 5.

During the spacewalk Tuesday, Whitson and Tani plan to remove up to 22 thermal covers around the race ring for a detailed inspection of all the bearings. They also plan to remove trundle bearing No. 5 for return to Earth aboard Atlantis.

"After we've inspected under as many panels as possible, we will bring in trundle bearing No. 5, unless we find one that we think was more of a problem," Whitson told reporters earlier today. "The ground has data that suggests that maybe that's where the problem is. But if we can visibly tell it's a different one, we'll bring in the one that we think is the troublemaker."

Whatever the problem might be, NASA needs to fix it and restore the right-side SARJ to normal operation as soon as possible to generate the electricity needed to support the Columbus module and two Japanese modules scheduled for launch in February and April.

The SARJ features two identical drive gears and two redundant drive motors. In a worst-case scenario, spacewalking astronauts could install fresh bearings on the undamaged race ring and reposition the drive lock assembly motors. The other option is to clean up the contamination that's present on the damaged race ring, fix whatever is causing the problem and resume normal operation.

"Once they have more data, they can make a better assessment of which of those approaches we should do, whether we should clean up the current race ring or just shift over," Whitson said. "Obviously, shifting over (to the other race ring) involves a lot more software changes and limits us on the timing. So the guys on the ground will have to make that decision. What we're providing (Tuesday) is additional data.

"I think either one's doable," she said. "To me, in my mind, I think it would be probably, from an astronaut's perspective, easier to just shift to the other race ring rather than trying to clean it up. But we don't know yet how easy that's going to be to clean up."

Kirk Shireman, deputy manager of the space station program at the Johnson Space Center, said no such decisions will be made until engineers have a better idea of what might be wrong.

"All options are still open," he said. "The big key question for us is what caused the issue, because we're hesitant to go to the only remaining ring we have on that side without understanding why this occurred. If you moved to the other ring and had the same problem, that's a really big issue for us. So we need to understand what's the root cause, what caused it to start and then propagate. We're working really hard to get that answer.

"There are some ideas, all kinds of ideas about how we could continue to use this ring for a while and then transition to the other ring," he said. "I don't think we've taken anything off the table at this point. I will tell you that most folks are thinking that we will go to the outboard ring at some point in time, it's just a matter of exactly when it makes sense to go and do that. It's not a very easy thing to do. It's a very EVA-intensive task and we do give up some redundancy."

A more immediate problem is fixing the S4-1A array's beta gimbal assembly, which is currently locked in place in an orientation that limits the panel's ability to generate electricity.

During routine operations Dec. 8, two circuit breakers tripped, possibly the result of a space debris impact that might have damaged the mechanism that allows power and data to flow through the rotary joint used to turn the array about its long axis. The trips also could be due to damage in critical cables.

Whitson and Tani plan to inspect the beta gimbal assembly and associated cables to look for signs of damage before moving onto the SARJ inspection.

"The idea is, we'll conduct the EVA right now, the SARJ inspection and the BGA inspection, and we'll learn what we need to learn," Shireman said. "Then we'll find the most opportune time to go fix it, not only the BGA but hopefully the SARJ. It really depends on how our analysis comes out. We'll be (working) to figure out exactly how long we can go with the BGA locked and the SARJ restrictions we have in place."

6:15 PM, 12/11/07, Update: Tanking test planned to help pinpoint ECO sensor problem

Engineers are drawing up plans to load the shuttle Atlantis' external tank with supercold liquid hydrogen next week in a critical test to pinpoint the source of elusive, intermittent electrical problems in low-level fuel sensors that derailed two launch attempts.

Shuttle Program Manager Wayne Hale said today engineers will tap into the engine cutoff - ECO - sensor circuitry near a control unit in the shuttle's aft engine compartment to hook up test instrumentation that should help locate any bad wiring or connectors in the 100 feet or so of cabling between the box and the sensors at the base of the external tank.

The tanking test is tentatively planned for next Tuesday.

"We think that we have some instrumentation we can put in an appropriate place in these circuits to observe what happens as we fill the tank," Hale told reporters during an afternoon teleconference. "If the erroneous condition repeats, which is what we think will happen, we can capture the location in the circuit of that opening with the use of some equipment and a technique known as time domain reflectivity, TDR.

"We have a high degree of confidence of pinpointing the location of where we're having our problems and once we know the location ... we'll be able to concentrate our go-forward efforts, presumably put together a fix and go fly. And again, our go-fly date is no earlier than Jan. 2. It could definitely be a little bit later than that, depending on the troubleshooting and the repair work involved."

The holiday work schedule also might play into the recovery plan.

"I am very concerned about team fatigue," Hale said. "We have worked our teams very hard the last several months and so we are in discussions about taking some days off on or about Christmas day, Christmas Eve, potentially the weekend before, to allow for crew rest.

"When we talk about no earlier than Jan. 2, part of the discussion is not only how quickly we can troubleshoot and fix this problem, but what is prudent to allow our folks to have a few days with their families and rest and recuperate. So I expect we'll be making that decision shortly after the tanking test."

The ECO sensors are part of a backup system intended to make sure the shuttle's main engines don't inadvertently suck a tank dry after some other problem - a leak, for example, or an improper hydrogen-oxygen mixture ratio - used up propellant at faster than normal rates. An engine running out of hydrogen during normal operation would have catastrophic consequences.

Early in the shuttle program, the ECO sensor launch commit criteria required three of four sensors to be operational for a countdown to proceed. That later was changed to a four-of-four requirement because of concern about lack of redundancy in part of the cicuitry. After modifications, the LCC was amended to three of four and that was the rule in place going into Atlantis' initial launch attempt.

The electrical resistance of platinum wires in the ECO sensors changes depending on whether they are exposed to cryogenic temperatures or not. A control unit called a point sensor box in an aft avionics bay monitors that resistance to determine whether a given sensor is wet - submerged in hydrogen - or dry, indicating the tank is nearly empty. That information, in turn, is passed along to the shuttle's flight computers.

Because of past problems with ECO sensors, engineers now send commands to simulate wet or dry conditions during the pre-launch tanking process. It was during a so-called "sim dry" test, when the ECO sensors were, in reality, submerged in hydrogen that problems cropped up for Atlantis.

During fueling for a Dec. 6 launch attempt, ECO sensors Nos. 3 and 4 "failed wet" about 35 minutes after they were submerged in liquid hydrogen at minus 423 degrees Fahrenheit. After the launch was called off, another sensor that shows when the tank is 5 percent full failed wet. After the tank was drained, ECO sensor No. 1 failed wet.

During fueling Dec. 9, ECO sensor No. 3 failed wet 24 minutes after the others were submerged. In both cases, the sensors returned to normal operation after the tank was drained and temperatures rose.

Because of past problems with the ECO sensors, new instrumentation is in place that lets engineers monitor voltage levels in the circuitry in real time. That provides an independent way to determine whether a sensor is working or not and some engineers suggested relying on that instrumentation to permit a launch even if one ore more sensors failed to work properly the second time around.

In an email to astronaut Bill McArthur, manager of safety and mission assurance for the shuttle program, Hale questioned whether the ECO sensor system has ever been truly reliable.

But NASA's Mission Management Team, acting on a proposal from the crew office, agreed to make a second launch attempt on Dec. 9 only if all four ECO sensors operated normally. During the second fueling, ECO sensor No. 3 failed wet about 24 minutes after submersion in hydrogen. No other problems were detected.

Hale told reporters today any talk of developing operational work arounds for dealing with ECO sensor anomalies was, for the time being at least, off the table.

"We have tabled that discussion," he said. "Our point is to try to fix this system. If we fix it, I would presume we would go back to the previously existing launch commit criteria (requiring three of four ECO sensors). If we come to a place where we're less than completely confident in our fix, then of course we would readdress the launch commit criteria."

Hale said there is about 100 feet of wiring between the point sensor box in the aft avionics bay and the ECO sensors at the base of the tank. The circuitry includes several connectors and wire splices.

Before next week's fueling test, engineers will climb into the aft engine compartment and tap into the wires running from the point sensor box to all for ECO sensors and the 5 percent sensor that failed wet during the first detanking.

"We're going to take five wires and cut them, install jumper cables to lead to the equipment that's outside of the orbiter," Hale said. "We're going to make that wire cut in the orbiter aft compartment close to the point sensor box in the avionics bay. We'll run the jumpers to the TDR equipment, which will be out on the mobile launch pad surface.

"We actually have to have people present to run that equipment. We can watch the instrumentation remotely but to physically switch from one sensor circuit to another on the TDR equipment, people have to be present. So we will send a red crew out during the stable replenish time frame.

"If the problem occurs during the fill as it has in the past, it would remain with us through the stable replenish time frame. We don't have people out on the launch pad during fill and drain operations because of the hazards involved. But we will send a red crew out when we're in the stable replenish mode."

Among candidate problem areas: Broken or damaged wires; a recessed connector pin/socket; contamination in a connector; wire splice damage; and a combination of problems leading to a tolerance "stack up" in a feed-through connector.

In addition to the tanking test, Hale said engineers will subject ECO sensor cables and harnesses to cryogenic conditions in a laboratory setting to collect additional insight into how they behave when the system is cooled to such low temperatures.

9:20 AM, 12/9/07, Update: Launch delayed to January; station crew told to plan for possible spacewalk to inspect stalled rotary joint (UPDATED at 11:30 a.m. with post-scrub briefing; troubleshooting options)

NASA's Mission Management Team today delayed launch of the shuttle Atlantis on a critical space station assembly mission to at least Jan. 2 to troubleshoot elusive, intermittent electrical problems with low-level hydrogen fuel sensors that derailed launch attempts Thursday and again this morning.

The shuttle's current launch window closes Dec. 13 because of space station power and temperature issues related to the lab's orbit. The window reopens Dec. 30, but NASA managers do not want to conduct a launch campaign during the end-of-year rollover because of countdown software issues.

Given the subtle nature of the problems with the engine cutoff - ECO - sensors at the base of Atlantis' external tank, managers concluded there was not enough time to attempt repairs before the current launch window expires.

Bill Gerstenmaier, chief of spaceflight operations at NASA headquarters, said the delay to January would not cause a major disruption to the space station assembly schedule. The next two flights in the sequence are scheduled for launch in mid February and late April. The next flight after that is an August mission to service the Hubble Space Telescope.

"If you look at what this means moving into January from a big-picture standpoint, it's not that big an impact to us overall, it won't impact the next mission, the February flight, we'll be able to accomplish that on time as planned," he said. "There's also some schedule time between that February flight and the April flight, there's a couple of weeks of margin in there so that can slip to the right.

"So from a big-picture standpoint, it's really not a big impact to us overall from an assembly of space station standpoint. There's enough margin in the system that we can accommodate this move into January without a big impact."

That's assuming, of course, engineers can track down and correct the ECO sensor problem by then. LeRoy Cain, director of shuttle integration at the Kennedy Space Center, said engineers plan to brief NASA managers Tuesday on possible troubleshooting options.

"We set up what we're calling our short-term KSC troubleshooting team to put together, brainstorm ideas and troubleshooting methods that we might want to go do for the system we have out at the launch pad," he said. "They're going to report out for the first time to the program board, the PRCB, on Tuesday of this week.

"From there we will determine what steps we take in the way of troubleshooting ... to include possibly a tanking test, to include possible looks at some of the feed-through connector areas and other wiring and cabling areas. ... They will bring their recommendations to us Tuesday."

How NASA might proceed from there, he said, will "depend on what we find out when we go begin to do some more in depth troubleshooting."

"We feel like we need to find root cause and we're going to make every effort to do that. Beyond that, as far as our path forward, it would be speculation for me at this point. Our main focus at this point is, given the repeat failure that we had today ... we're very hopeful it will repeat again in a fashion that we can capture it and be able to narrow down the area that's causing the problem, whether it be in the tank or outside of the tank or somewhere in the connectors. That's really our main focus right now."

Said Gerstenmaier: "Data is data. Whether it helps us find the specific failure or it rules out all the things that can't be causing the failure, that helps us figure out a way to build better operational rules to fly safe and continue with the manifest."

He was referring to the possibility of developing rationale for flight with one or more failed ECO sensors by incorporating procedures utilizing new instrumentation to monitor the status of each sensor.

"We have a lot of options in front of us before, if and when, we would need to roll back" to the Vehicle Assembly Building where Atlantis can be removed from the tank for more extensive troubleshooting. "So we're going to consider the recommendations the team brings forward Tuesday. The Tuesday recommendations and any troubleshooting we might do while we have this system out at the launch pad allows usÊthe opportunity to fly as early as Jan. 2. If we determine subsequently that we need to roll back and do more invasive kind of work, then that probably does not support Jan. 2."

Telemetry indicates a possible open circuit somewhere between an electronic unit in the shuttle's engine compartment and the sensors themselves. Launch Director Doug Lyons said the box is easily accessible at the launch pad, along with much of the wiring that runs through the belly of the shuttle and into the tank.

"In terms of our capabilities out at the launch pad, we've got very good access, particularly inside the orbiter aft so that there's almost limitless troubleshooting we can do there," Lyons said. "And we've got very good access to the tank. So we can do extensive troubleshooting out there before we would entertain rolling back. There's not many things we can't do out at the launch pad that we could do in the VAB."

In the meantime, flight controllers informed space station commander Peggy Whitson and her crewmates of the launch delay and told her she and Tani likely will be asked to carry out a spacewalk later this month to inspect a problematic solar array rotary joint on the right side of the lab's main power truss.

If Atlantis had gotten off the pad during the current window, NASA managers planned to add a fourth spacewalk to the shuttle mission to carry out the solar alpha rotary joint - SARJ - inspection.

Because of recently discovered contamination in the massive gear-driven joint, used to rotate outboard arrays to keep them face on to the sun, the starboard SARJ has been locked in place pending additional analysis.

NASA needs to fix the joint and restore it to normal, or near normal, operation before a sophisticated Japanese research module can be launched in April.

A SARJ inspection spacewalk by Whitson and Tani likely would be carried out before Dec. 21. An unmanned Russian Progress supply ship is scheduled for launch from the Baikonur Cosmodrome in Kazakhstan on Dec. 23 with docking on tap the day after Christmas.

7:00 AM, 12/9/07, Update: ECO sensor No. 3 fails initial health check (UPDATED at 7:30 a.m. with official launch scrub; UPDATED at 8:40 a.m. with comments from launch director)

Dashing hopes of finally launching shuttle Atlantis on a critical space station assembly mission today, one of the four low-level engine cutoff - ECO - sensors in the hydrogen section of the shuttle Atlantis' external tank failed to perform properly during initial tests after being submerged in supercold propellant. NASA managers said Saturday they would proceed with launch today if and only if all four sensors and associated instrumentation worked flawlessly and at 7:25 a.m., today's launch attempt was officially called off.

Fueling began at 5:56 a.m. and by 6:48 a.m., the loading process transitioned to "fast fill." A few minutes later, launch control commentator George Diller reported what engineers initially believed was good news.

"The liquid hydrogen sensors have been cycled and they are all confirmed to be working properly," he said. "Once again, at this time, all four liquid hydrogen sensors are working. This was somewhat predicted based on past tanking attempts when we had a problem with the sensors and then tanked a second time and the sensors have worked properly. So right now, this is consistent with our experience base. And all four hydrogen sensors are currently operating."

But moments later, sensor No. 3 apparently failed.

"One of the liquid hydrogen sensors, No. 3, has failed," Diller said. "Standing by for further action. ... This is not good news."

Engineers continued filling Atlantis' external tank to collect additional data. NASA has a flight rule that permits a launch if three of four sensors are working properly. But during fueling for an initial launch attempt Thursday, three of the four sensors, including No. 3, did not respond properly. Because the system is suspect - and because repairs are not possible before the end of the current launch window Dec. 13 - NASA's Mission Management Team required all four sensors and associated instrumentation to be working properly today for the countdown to proceed.

"As planned, we came in and picked up with our tanking operations," Launch Director Doug Lyons explained later. "There's a sequence of events we go through, we chill the lines down and we get into a slow fill to condition the facility lines as well as the orbiter. And ultimately, we get into what we call fast fill. And that's where we've been experiencing these failures.

"So we were going through that process, we had gotten to fast fill. There are two things we look at: the voltages on the circuit, and those were all good on all four circuits, and we also look at the discretes, whether they're indicating wet or if they're indicating dry. And all of them went wet as expected. Once we were in fast fill for roughly 10 minutes or so, we went and did system checkout and that's when we send simulated dry commands to the sensors sequentially and see if they go from wet to dry. And if they do operate in that manner, that's what we're expecting and that's a good checkout.

"So we were watching, of course, with great interest in the firing room," Lyons continued. "We started the test and sensor number 1 went dry. Sensor number 2 went dry. Sensor number 3 - and if you recall, 3 and 4 were the ones that failed last tanking - 3 went dry and 4 went dry. All the voltages were reading good values as well. So it looked like we had a good system and of course, the firing room, we were very excited and felt like we had a good system and we'd be ready to go fly today.

"We continued to monitor the system and two or three minutes after this test went on, they were all dry and we were keeping them in that condition. And then we saw sensor number 3 go from dry to wet, which was a failure. At that point, based on our revised LCC (launch commit criteria), which calls for four-of-four sensors, we were scrubbed for the day."

Additional checks were made and in each case, he said, sensor No. 3 remained in the wet state, indicating an open circuit.

"On Thursday, sensors 3 and sensor 4 failed," Lyons said. "In this case, onlyÊ sensor 3 failed. But they failed in generally the same time frame and in the same manner. We have seen in the past when we've had an open circuit and we've come back and tanked, the sensor corrected itself and operated properly. And that's what we did see with sensor number 4, but we just didn't have any joy with sensor number 3."

Lyons would not speculate on what mission managers might decide about where to go from here. A Mission Management Team meeting was scheduled to begin at 9 a.m.

"We do have multiple options and folks have been thinking about what ifs," he said. "We'll put something together and be ready to implement it coming out of that meeting."

The goal of Atlantis' mission is to deliver the European Space Agency's Columbus research lab to the international space station, along with French astronaut Leopold Eyharts. Eyharts will replace Expedition 16 flight engineer Dan Tani and oversee the activation of the Columbus module.

Three spacewalks are planned to prepare Columbus for installation; to install two experiments on its hull; and to replace a spent nitrogen tank used to pressurize the station's ammonia cooling system. The nitrogen tank and a failed gyroscope will be moved back to the shuttle for return to Earth.

But NASA only has until Dec. 13 to get Atlantis off the ground because of temperature and power issues related to the angle between the sun and the plane of the space station's orbit. The window reopens Dec. 30, but any delay past Dec. 13 would push the flight into January to avoid countdown software issues due to the end-of-year rollover.

Engineers cannot access all of the ECO sensor circuitry at the launch pad, raising the possibility of a rollback to the Vehicle Assembly Building to remove the orbiter from the external tank for more extensive troubleshooting. But no such decisions have been made as of this writing.

An update will be posted here as soon as more information is available.

The ECO sensors are part of a backup system intended to detect low fuel levels in time to prevent the shuttle's main engines from draining the tank after some other problem that might cause the powerplants to use up hydrogen faster than expected. Running out of fuel during engine operation likely would trigger a catastrophic failure.

In the wake of earlier problems with the cutoff sensors, NASA implemented a flight rule change that would permit a countdown to proceed if three of four sensors were operating normally and certain other conditions were met.

But engineers do not yet know what caused two sensors to "fail wet" during fueling Thursday or why a third sensor did the same during de-tanking operations. Because the system is suspect, the flight crew office proposed proceeding with launch Sunday if, and only if, all four sensors are operating normally.

7:20 PM, 12/8/07, Update: NASA clears Atlantis for Sunday launch try

NASA's Mission Management Team today cleared the shuttle Atlantis for a second launch attempt Sunday, but agreed that any additional problems with suspect low-level hydrogen fuel sensors in the ship's external tank will trigger another delay.

In additional to requiring that all four engine cutoff - ECO - sensors in the shuttle's hydrogen tank work flawlessly, the MMT also said new instrumentation that monitors the status of the sensors must be in perfect working order as well.

For the first time, data from that instrumentation will be used during ascent to give flight controllers insight into the health of the sensors and the shuttle's launch window will be reduced from five minutes to just one minute to ensure Atlantis takes off with enough fuel to protect against worst-case failures that otherwise might drain the tank faster than expected.

"Tomorrow, we've decided to go tank and if everything works perfectly, as we would expect from our past history, we'll go fly," said shuttle Program Manager Wayne Hale. "And if we have any other anomalies, or a repeat of an anomaly, then we think it is worthwhile to stand down and troubleshoot. The nature of that troubleshooting and how long it would take is a little bit open ended. We'll wait to see what happens before we decide that. But suffice it to say we would not be launching tomorrow and it probably would reduce our chances of launching in the December launch window substantially."

But if the hardware cooperates, "we're going to give it a shot tomorrow," he said.

Engineers plan to begin pumping a half-million gallons of liquid oxygen and hydrogen rocket fuel into Atlantis' external tank starting at 5:55 a.m. Sunday. If all goes well, commander Steve Frick and his six crewmates - pilot Alan Poindexter, flight engineer Rex Walheim, Leland Melvin, Stan Love and European astronauts Hans Schlegel and Leopold Eyharts will begin strapping in shortly after 12 p.m.

Launch is targeted for 3:21:00 p.m., roughly the moment Earth's rotation carries the launch pad into the plane of the space station's orbit. Forecasters predict a 70 percent chance of good weather Sunday and Monday.

The shuttle has enough fuel to launch five minutes to either side of the "in-plane" time and still catch up with the space station. But NASA typically targets the middle of the 10-minute window, giving a crew just five minutes or so to get off the ground.

For Atlantis' launch, the window has been shortened to just one minute beyond the 3:21 p.m. in-plane time. Launching later in the window would require more fuel to catch up with the space station and NASA managers want to ensure Atlantis has ample reserves to avoid any chance of an engine shutdown due to propulsion problems and trouble with the low-level fuel sensors.

Three of four engine cutoff sensors in the hydrogen section of the shuttle's external tank failed to respond properly during tests to verify their health shortly after fueling began for an initial launch attempt last Thursday. The sensors later returned to normal operation and NASA managers tentatively decided late Friday to set up for another launch attempt Sunday.

The ECO sensors are part of a backup system intended to detect low fuel levels in time to prevent the shuttle's main engines from draining the tank after some other problem that might cause the powerplants to use up hydrogen faster than expected. Running out of fuel during engine operation likely would trigger a catastrophic failure.

In the wake of earlier problems with the cutoff sensors, NASA implemented a flight rule change that would permit a countdown to proceed if three of four sensors were operating normally and certain other conditions were met.

But engineers do not yet know what caused two sensors to "fail wet" during fueling Thursday or why a third sensor did the same during de-tanking operations. Because the system is suspect, the flight crew office proposed proceeding with launch Sunday if, and only if, all four sensors are operating normally.

The health of the sensors will be monitored throughout the countdown, using computer commands to simulate wet and dry conditions. The first such 'sim test" will occur early in the fueling process with additional checks planned at various points in the countdown. Voltage readings will be monitored all way to the T-minus 31-second mark when the shuttle's flight computers take over the countdown.

Using the new instrumentation, flight controllers will be able to determine whether any sensors fail after launch, allowing the crew to take action to preclude any potentially catastrophic downstream failures. Those options include aborting to a lower-than-planned orbit, dumping maneuvering fuel overboard to lighten the ship or diverting to an emergency landing in Spain or France.

All of those worst-case scenarios, Hale stressed, would require multiple failures in unrelated systems. As such, program managers and engineers decided it was safe to proceed with launch.

There is some reason to believe the sensors will work normally the second time around. Similar problems have gone away during past launch campaigns after initial exposure to minus 423-degree hydrogen fuel. Whether all four sensors will cooperate Sunday remains to be seen.

But Launch Director Doug Lyons said anything less than normal behavior from the sensors and the new instrumentation that monitors their performance will stop the countdown and result in another launch delay. Whether NASA would make any additional launch tries before the current window closes Dec. 13 is not yet known.

Today's decision to proceed with another launch try, even with more restrictive launch rules and requirements, was opposed by some engineers who argued for standing down and conducting additional tests to determine what might be causing the problem.

But in the end, the MMT voted to proceed with flight.

"Could something happen despite all our caution? Yes," Hale said. "This is a risky business."

01:45 PM, 12/8/07, Update: Engineers troubleshoot circuit breaker trips on space station solar arrays

NASA and contractor managers and engineers are reviewing plans to make a second attempt to launch the shuttle Atlantis Sunday despite problems with troublesome low-level fuel tank sensors that derailed a launch try Thursday.

Three of four engine cutoff - ECO - sensors in the hydrogen section of the shuttle's external tank failed to respond properly during tests to verify their health shortly after fueling began. They later returned to normal operation and NASA managers tentatively decided late Friday to set up for another launch attempt Sunday.

At that time, space shuttle Program Manager Wayne Hale said if one or more ECO sensors failed to operate properly at any point in the countdown Sunday, the launch would be called off. But that plan still requires final approval and some senior managers favor standing down for repairs.

NASA's Mission Management Team began meeting at 1 p.m. today and a final decision on how to proceed is expected later this afternoon.

The ECO sensors are part of a backup system intended to detect low fuel levels in time to order a main engine shutdown if some other problem caused the powerplants to use up hydrogen faster than expected. At least two sensors must be operational for the system to work.

In the wake of earlier problems with the cutoff sensors, NASA implemented a flight rule exception that would permit a countdown to proceed if three of four sensors were operating normally and certain other conditions were met.

But engineers do not yet know what caused two sensors to "fail wet" during fueling Thursday or why a third sensor did the same during de-tanking operations. Because the system is suspect, the flight crew office proposed proceeding with launch Sunday if, and only if, all four sensors are operating normally.

Other proposed safeguards include shortening the launch window to one minute to reduce the amount of fuel need to catch up with the station and thus provide a cushion to protect against any possible low-level engine shut downs. In addition, flight controllers would incorporate data from new instrumentation for the first time to monitor the status of the sensors during ascent.

There is some reason to believe the sensors will work normally the second time around. Similar problems have gone away during past launch campaigns after initial exposure to minus 423-degree hydrogen fuel. Whether all four sensors will cooperate Sunday remains to be seen.

Assuming engineers get the green light, fueling will begin at 5:55 a.m. Sunday for a launch attempt at 3:21 p.m. Engineers plan to test the ECO sensors throughout the countdown, beginning shortly after they are submerged in liquid hydrogen around 6:41 a.m.

The goal of Atlantis' mission is to deliver the European Space Agency's Columbus research lab to the international space station along with French astronaut Leopold Eyharts, who will replace Expedition 16 flight engineer Dan Tani.

Tani, Expedition 16 commander Peggy Whitson and Russian flight engineer Yuri Malenchenko ran into problems earlier today with circuit breaker trips that briefly prevented flight controllers from changing the orientation of a right-side solar panel as required for the shuttle's docking next week.

The trouble involved one of the two wings making up the starboard 4, or S4, array on the right side of the station's main power truss. Those arrays currently are prevented from rotating to track the sun by earlier trouble with a massive rotary joint.

Concern about the solar alpha rotary joint, or SARJ, is behind a push to add a fourth spacewalk to Atlantis' mission. Engineers want a detailed inspection to help them figure out what might be wrong and what might be needed to fix it.

While unable to rotate paddle-wheel style, the two S4 solar wings also can be turned about their long axis, much like changing the pitch of an airplane propeller, to maximize electrical output. Early today, however, one or more remote power control modules, which act like circuit breakers, tripped open and stalled the so-called beta gimbal joint used to turn the S4-1A array.

Space station solar array motions: The red arrows indicate the motion of the arrays provided by two solar alpha rotary joints on either side of the station's main power truss. The blue arrows indicate the motion provided by beta gimbal assemblies. Only one set of arrays - starboard 4 - is currently in place on the right side of the power truss. In the above graphic, the S4-1A and 3A arrays are second from the left. The outermost right-side arrays - S6 - are scheduled for launch next year.

The circuit breaker trips are not expected to have any impact on the Atlantis mission.

Here is a revised countdown timeline for Sunday's proposed shuttle launch attempt (in EST):

EST...........EVENT

12:06 AM......Fuel cell activation
12:56 AM......Booster joint heater activation
01:26 AM......MEC pre-flight bite test
01:41 AM......Tanking weather update
01:56 AM......Final fueling preps; launch area clear
02:56 AM......Red crew assembled
03:41 AM......Fuel cell integrity checks complete

03:55 AM......Begin 2-hour built-in hold (T-minus 6 hours)
04:06 AM......Safe-and-arm PIC test
05:11 AM......Mission management team tanking meeting
05:00 AM......Crew wakeup
05:26 AM......Test team ready for ET loading
05:55 AM......Resume countdown (T-minus 6 hours)

05:55 AM......LO2, LH2 transfer line chilldown
06:00 AM......NASA TV coverage of fueling begins
06:06 AM......Main propulsion system chill down
06:06 AM......LH2 slow fill
06:36 AM......LO2 slow fill
06:41 AM......Hydrogen ECO sensors go wet
06:46 AM......LO2 fast fill
06:56 AM......LH2 fast fill
08:51 AM......LH2 topping
08:56 AM......LH2 replenish
08:56 AM......LO2 replenish

08:55 AM......Begin 2-hour 30-minute built-in hold (T-minus 3 hours)
08:55 AM......Closeout crew to white room
08:55 AM......External tank in stable replenish mode
09:26 AM......Astronaut support personnel comm checks
09:55 AM......Crew breakfast/photo op (recorded)
10:00 AM......NASA television coverage begins
10:01 AM......Pre-ingress switch reconfig
11:01 AM......Final crew weather briefing
11:11 AM......Crew suit up begins
11:25 AM......Resume countdown (T-minus 3 hours)

11:31 AM......Crew departs O&C building
12:01 PM......Crew ingress
12:51 PM......Astronaut comm checks
01:16 PM......Hatch closure
02:01 PM......White room closeout

02:05 PM......Begin 10-minute built-in hold (T-minus 20m)
02:16 PM......NASA test director countdown briefing
02:15 PM......Resume countdown (T-minus 20m)

02:17 PM......Backup flight computer to OPS 1
02:21 PM......KSC area clear to launch

02:26 PM......Begin final built-in hold (T-minus 9m)
02:57 PM......NTD launch status verification
03:12:00 PM...Resume countdown (T-minus 9m)

03:13:30 PM...Orbiter access arm retraction
03:16:00 PM...Launch window opens
03:16:00 PM...Hydraulic power system (APU) start
03:16:05 PM...Terminate LO2 replenish
03:17:00 PM...Purge sequence 4 hydraulic test
03:17:00 PM...IMUs to inertial
03:17:05 PM...Aerosurface profile
03:17:30 PM...Main engine steering test
03:18:05 PM...LO2 tank pressurization
03:18:25 PM...Fuel cells to internal reactants
03:18:30 PM...Clear caution-and-warning memory
03:19:00 PM...Crew closes visors
03:19:03 PM...LH2 tank pressurization
03:20:10 PM...SRB joint heater deactivation
03:20:29 PM...Shuttle GPCs take control of countdown
03:20:39 PM...SRB steering test
03:20:53 PM...Main engine start (T-6.6 seconds)
03:21:00 PM...SRB ignition (LAUNCH)

10:52 PM, 12/7/07, Update: NASA tentatively resets shuttle launch for Sunday pending final analysis; all engine cutoff sensors must operate normally to permit launch

Hoping critical fuel sensors will work properly the second time around, NASA managers today tentatively rescheduled the shuttle Atlantis for a delayed launch Sunday afternoon to kick off a high-profile mission to deliver Europe's Columbus research module to the international space station. With forecasters predicting a 70 percent chance of good weather, liftoff is targeted for 3:21 p.m. assuming no major problems turn up in a final round of engineering reviews Saturday.

"The team has taken a very thorough and measured approach to this," said shuttle Program Manager Wayne Hale. "We're very cognizant of the fact that you don't like to accept risk at the launch site, we don't want to get launch fever. Even though the Columbus is out there loaded in the payload bay and everybody is anxious for us to launch that guy, we want to make sure when we go launch it is safe, or at least as safe as it ever is in this normally risky business."

The long-awaited flight was delayed Thursday when two of four engine cutoff sensors in the hydrogen section of the shuttle's external tank failed to respond properly during fueling. A third sensor later acted up during the de-tanking procedure. NASA managers considered launching Atlantis as is Saturday, but after a long debate they tentatively decided to proceed toward an attempt Sunday if additional reviews show the plan is safe and if all four sensors are operating properly.

While engineers do not know what might be causing the problem, past experience with balky sensors shows they tend to work normally during subsequent fueling operations.

In addition, the shuttle's launch period - normally about five minutes long - will be shortened to around one minute right around the moment Earth's rotation carries the launch pad into the plane of the space station's orbit. That will minimize the amount of propellant needed to catch up with the lab complex and provide a reserve to protect against unexpected failures and additional sensor problems that might otherwise trigger a premature engine shutdown.

As an additional precaution, new instrumentation designed to monitor the health of the engine cutoff - ECO - sensors will be used in mission control during ascent to keep tabs on the circuits in case of failures that might require action by the crew.

"The crew office, the flight crew actually came with a very positive proposal in my view today," Hale said. "They said let us tighten up our launch commit criteria and require all four of these sensors to be working, plus the new instrumentation we've added that measures voltage in the middle of this system, which is new on the last couple of flights, require all four of those measurements to be working. And if all of that stuff is working and we restrict our launch to a very short window around the most optimum time to give ourselves the maximum performance benefit, then with some new flight rules that the mission operations people back in Houston are implementing, the flight crew believes it would be acceptably safe for us to go fly with some additional risk."

Not everyone agreed. But Hale sided with the flight crew office, saying "I personally believe this is a great proposal."

"However, we want to run down a number of the technical aspects," he said. "We are still facing a situation where we don't know root cause. If we tank the vehicle up and we have these sensors act up again, we certainly would want to stand down again because that's outside our experience base. So the proposal is on the table."

NASA's MIssion Management Team plans to reconvene at 1 p.m. Saturday to review final engineering assessments. If no major problems are found, the team will proceed toward a launch attempt Sunday.

"If we find this proposal that the flight crew office has offered allows us to fly with acceptable risk, we'll try to tank up the vehicle and launch on Sunday," Hale said. "If, on the other hand, as we think about it and review it for the next several hours and think this is not a good plan, then we will stand down and do something different. So it's the nature of spaceflight. Here we are. When I come down for a shuttle launch, I always pack enough clothes to last through the entire launch window. I hope you guys did."

Engineers do not yet know what caused ECO sensors 3 and 4 to fail a test during fueling Thursday and they don't know if the devices or associated circuitry will malfunction again Sunday. NASA has a flight rule exception that permits a launch with three of four operational ECO sensors but because the system aboard Atlantis is considered suspect, engineers today decided to require four operational sensors for a launch to proceed.

If any one of the sensors fails after fueling Sunday, the launch will be called off.

Under the revised timeline, engineers will begin pumping a half-million gallons of super-cold liquid oxygen and hydrogen rocket fuel into the shuttle's external tank at 5:56 a.m. Sunday. The four engine cutoff sensors at the base of the tank will be submerged in liquid hydrogen, at minus 423 degrees Fahrenheit, by 6:41 a.m. and tests to confirm their health will begin shortly thereafter.

The three-hour fueling process should be complete by 8:56 a.m. and the astronauts - commander Steve Frick, pilot Alan Poindexter, flight engineer Rex Walheim, Leland Melvin, Stan Love and European astronauts Hans Schlegel and Leopold Eyharts - are scheduled to begin strapping in around 12:01 p.m.

Launch is targeted for 3:21:00 p.m. Assuming an on-time liftoff, Atlantis will dock with the space station around 12:08 p.m. Tuesday. The European Space Agency's Columbus module will be attached to the station during a spacewalk the next day.

Frick and company plan three spacewalks to prepare the Columbus module for attachment to the station; to move an empty nitrogen tank and a failed gyroscope to the shuttle for return to Earth; and to install two external experiments on the hull of the new lab module.

NASA managers want to add a fourth spacewalk if possible to permit a detailed inspection of a stalled solar array rotary joint to help engineers figure out what sort of repairs might be needed to get the joint turning smoothly again. But an additional spacewalk would require a two-day mission extension and that, in turn, is based on how much hydrogen and oxygen is available to power the ship's fuel cells.

Engineers took advantage of the Thursday launch delay to top off the shuttle's on-board fuel cell hydrogen supply. As a result, NASA can make two launch attempts Sunday and Monday before standing down for 72 hours to re-load hydrogen and oxygen for the fuel cell system. That would permit a final launch try Dec. 13, the day the shuttle's launch window closes for the year.

Assuming a launch Sunday and a two-day mission extension, Atlantis would return to the Kennedy Space Center on Dec. 22. And in all cases, the launch strategy assumes all four ECO sensors work properly when submerged in cryogenic propellant.

The sensors in question are part of a backup system intended to ensure a safe engine shutdown if some other problem caused the shuttle to use its hydrogen fuel faster than expected.

LeRoy Cain, chairman of NASA's Mission Management Team at the Kennedy Space Center, told reporters late Thursday the problem appeared to be an open circuit somewhere in the wiring between an electronic component in the shuttle's engine compartment and the sensors at the bottom of the hydrogen tank.

Given access problems and an eight-day launch window that closes for the year Dec. 13, the MMT ruled out opening the aft for any possible inspections or repairs. Instead, NASA focused on developing possible workarounds that would permit launching Atlantis as is with two or more suspect low-level cutoff sensors.

The ECO sensors would only be needed late in the climb to space if some other problem - a leak, for example, or a hydrogen-rich mixture ratio in the main engines - caused the shuttle to burn up its hydrogen supply faster than expected. Without the ECO sensors, the engines could drain the tank and suffer catastrophic oxygen-rich shutdowns. The ECO sensors are in place to ensure a safe engine shutdown before any damage could occur.

Atlantis could launch with just two operational ECO sensors. But in that case, one additional failure could trigger a premature engine shutdown because the software has to protect against the possibility that the remaining sensor could fail or indicate the wrong state.

NASA has had major problems with the ECO sensors in the initial post-Columbia flights and the agency recently developed new instrumentation to provide voltage readings that can show whether the sensors, which only indicate whether they are wet or dry, have changed state. The instrumentation is used during countdowns to monitor the sensors, but the data is not yet implemented in any ascent procedures.

Given the problems with Atlantis' ECO sensors, Cain asked engineers to look into the possibility of using that instrumentation during the climb to space to give flight controllers a way to assess the health of the sensors in flight. That would provide the insight needed to order a manual engine shutdown if needed.

The odds of the multiple failures that would have to occur to trigger an abort in this context are considered remote. The shuttle's flight computers only monitor the state of the sensors during the final seconds of powered flight when the tank is nearly empty. But NASA managers could not agree today to launch Atlantis with two of four sensors. Instead, they tentatively decided to fill the tank for a Sunday attempt and proceed to launch but only if all four sensors are operating normally.

But even if all four ECO sensors are operating normally at launch, there is still additional risk.

"The additional risk, of course, is that these sensors have not functioned as we expected them to," Hale said. "And even if they do come back and function well the next time we tank, which has been our experience, there is some risk that once you launch and you get into the shake, rattle and roll of actual flight that these sensors might once again start failing, presumably to this open circuit state, so you would lose this low-level protection.

"And then, if you had lost enough sensors so that you didn't have low-level protection - I'm talking about the whole circuit involved here - then if you incurred some other problem that would cause you to run short onÊhydrogen fuel, you would be forced to either take the abort action or you would be facing a catastrophic event.

"We would like to have certainty," he said. "We would like to know root cause. We are not likely to have certainty or root cause and be able to launch in this window. So we're thinking about our options and whether the risks involved are acceptable or not."

Assuming the MMT opts to proceed, here is a revised countdown for Sunday's launch activity (in EST):

EST...........EVENT

12:06 AM......Fuel cell activation
12:56 AM......Booster joint heater activation
01:26 AM......MEC pre-flight bite test
01:41 AM......Tanking weather update
01:56 AM......Final fueling preps; launch area clear
02:56 AM......Red crew assembled
03:41 AM......Fuel cell integrity checks complete

03:56 AM......Begin 2-hour built-in hold (T-minus 6 hours)
04:06 AM......Safe-and-arm PIC test
05:11 AM......Mission management team tanking meeting
05:08 AM......Crew wakeup
05:26 AM......Test team ready for ET loading
05:56 AM......Resume countdown (T-minus 6 hours)

05:56 AM......LO2, LH2 transfer line chilldown
06:06 AM......Main propulsion system chill down
06:06 AM......LH2 slow fill
06:36 AM......LO2 slow fill
06:41 AM......Hydrogen ECO sensors go wet
06:46 AM......LO2 fast fill
06:56 AM......LH2 fast fill
08:51 AM......LH2 topping
08:56 AM......LH2 replenish
08:56 AM......LO2 replenish

08:56 AM......Begin 2-hour 30-minute built-in hold (T-minus 3 hours)
08:56 AM......Closeout crew to white room
08:56 AM......External tank in stable replenish mode
09:26 AM......Astronaut support personnel comm checks
10:01 AM......Pre-ingress switch reconfig
10:08 AM......NASA television coverage begins
10:18 AM......Crew breakfast/photo op (recorded)
11:01 AM......Final crew weather briefing
11:11 AM......Crew suit up begins
11:26 AM......Resume countdown (T-minus 3 hours)

11:31 AM......Crew departs O&C building
12:01 PM......Crew ingress
12:51 PM......Astronaut comm checks
01:16 PM......Hatch closure
02:01 PM......White room closeout

02:06 PM......Begin 10-minute built-in hold (T-minus 20m)
02:16 PM......NASA test director countdown briefing
02:16 PM......Resume countdown (T-minus 20m)

02:17 PM......Backup flight computer to OPS 1
02:21 PM......KSC area clear to launch

02:27 PM......Begin final built-in hold (T-minus 9m)
02:57 PM......NTD launch status verification
03:12:00 PM...Resume countdown (T-minus 9m)

03:13:30 PM...Orbiter access arm retraction
03:16:00 PM...Launch window opens
03:16:00 PM...Hydraulic power system (APU) start
03:16:05 PM...Terminate LO2 replenish
03:17:00 PM...Purge sequence 4 hydraulic test
03:17:00 PM...IMUs to inertial
03:17:05 PM...Aerosurface profile
03:17:30 PM...Main engine steering test
03:18:05 PM...LO2 tank pressurization
03:18:25 PM...Fuel cells to internal reactants
03:18:30 PM...Clear caution-and-warning memory
03:19:00 PM...Crew closes visors
03:19:03 PM...LH2 tank pressurization
03:20:10 PM...SRB joint heater deactivation
03:20:29 PM...Shuttle GPCs take control of countdown
03:20:39 PM...SRB steering test
03:20:53 PM...Main engine start (T-6.6 seconds)
03:21:00 PM...SRB ignition (LAUNCH)
 

3:23 PM, 12/7/07, Update: Engineers assess launch options

NASA and contractor managers and engineers are meeting today to discuss whether to implement hurried workarounds that could clear the way for launch of the shuttle Atlantis Saturday despite suspect engine cutoff sensors in the ship's external tank.

The sensors are part of a backup system intended to ensure a safe engine shutdown if some other problem caused the shuttle to use its hydrogen fuel faster than expected. Two of four sensors, or their associated circuitry, failed to operate properly during fueling Thursday, forcing NASA to call off an attempt to launch Atlantis and Europe's Columbus research module to the international space station.

LeRoy Cain, chairman of NASA's Mission Management Team at the Kennedy Space Center, told reporters late Thursday the problem appears to be an open circuit somewhere in the wiring between an electronic component in the shuttle's engine compartment and the sensors at the bottom of the hydrogen tank.

Given access problems and an eight-day launch window that closes for the year Dec. 13, Cain said there were no plans to open the aft for any possible repairs. Instead, NASA is focusing on developing possible workarounds that would permit launching Atlantis as is with two or more suspect low-level cutoff sensors.

If NASA managers decide to proceed, fueling would begin at 6:18 a.m. Saturday for a launch attempt at 3:43:31 p.m. A news conference to discuss NASA's plans is expected after today's Mission Management Team meeting.

The ECO sensors would only be needed if some other problem - a leak, for example, or a hydrogen-rich mixture ratio in the main engines - caused the shuttle to burn up its hydrogen supply faster than expected. Without the ECO sensors, the engines could drain the tank and suffer catastrophic failures. But if any two of the four ECO sensors suddenly changed from "wet" to "dry," the shuttle's computers would order a safe engine shutdown before any damage could occur.

Atlantis could safely launch with two operational ECO sensors. But in that case, one additional failure could trigger a premature engine shutdown because the software has to protect against the possibility that the remaining sensor could fail.

NASA has had major problems with the ECO sensors in the initial post-Columbia flights and the agency recently developed new instrumentation to provide voltage readings that can show whether the sensors, which only indicate whether they are wet or dry, have changed state. The instrumentation is used during countdowns to monitor the sensors, but the data is not yet implemented in any ascent procedures.

Given the problems with Atlantis' ECO sensors, Cain said he had asked engineers to look into the possibility of using that instrumentation during the climb to space to give flight controllers a way to assess the health of the sensors in flight. That would provide the insight needed to order a manual engine shutdown if needed.

But if only two of four sensors are considered operational at launch, another failure in flight could force the crew to initiate an abort to protect against the possibility of a subsequent failure. That's a scenario that would not necessarily be in play if a third sensor was operational at launch.

The odds of the multiple failures that would have to occur to trigger an abort in this context are considered remote. But NASA has a long-standing policy of not changing critical flight requirements in the heat of a countdown and it remains to be seen whether commander Steve Frick and his crew, along with ascent flight director Norm Knight and the mission control team, would agree with any plans to launch with two suspect ECO sensors.

This status report will be updated as soon as possible after today's MMT meeting.

9:45 PM, 12/6/07, Update: Launch delayed at least 48 hours; engineers trying to develop rationale to fly as is

After a five-hour Mission Management Team meeting, NASA managers today decided to delay the shuttle Atlantis' launch on a space station assembly mission until Saturday at the earliest because of problems with the circuitry associated with critical engine cutoff sensors in the ship's external tank.

Based on electrical data seen during fueling today, engineers believe the problem involves an open circuit in the wiring between an electronic box in the shuttle's engine compartment and the sensors at the base of the hydrogen section of the external tank. Given the shuttle's short eight-day launch window, NASA managers today ruled out opening up the engine compartment to attempt any inspections of repairs.

Instead, the team is focusing on developing flight rationale for launching Atlantis as is, using manual procedures to monitor the sensors during ascent to prevent any potentially catastrophic problems.

LeRoy Cain, chairman of NASA'S Mission Management Team at the Kennedy Space Center, told reporters late today engineers will meet again Friday to reconsider their options, adding they may not get comfortable with a fly-as-is rationale in time for a Saturday launch.

In the meantime, NASA managers ruled out a fueling test Friday and decided instead to top off the shuttle's onboard supply of liquid hydrogen to power the ship's electricity producing fuel cells. That would permit launch attempts Saturday and Sunday and still provide enough on-board supplies for a two-day mission extension and the addition of a fourth spacewalk.

Three spacewalks are required to connect the European Columbus research lab to the station; to replace a nitrogen coolant system pressurization tank; to install a pair of experiments on the Columbus module; and to move a failed space station gyroscope to the shuttle for return to Earth.

NASA managers want to add a fourth spacewalk if possible to permit a detailed inspection of a stalled solar array rotary joint to help engineers figure out what sort of repairs might be needed to get the joint turning smoothly again. But an additional spacewalk would require a two-day mission extension and that, in turn, is based on how much hydrogen and oxygen is available to power the ship's fuel cells.

A launch on Saturday, assuming the engine cutoff sensor problem can be resolved, would be targeted for 3:43:31 p.m., setting up a docking with the international space station around 12:56 p.m. Monday. The forecast for Saturday calls for a 60 percent chance of good weather, improving to 70 percent "go" on Sunday.

Atlantis' launch window closes Dec. 13 because of power and temperature issues related to the space station's orbit. The window reopens Dec. 30, but senior NASA managers have said launch would be delayed to at least Jan. 2 if the shuttle team misses the current window.

NASA managers had high hopes for a launching today, with a forecast calling for a 90 percent chance of good weather and no technical problems of any significance at pad 39A. After a short 13-minute Mission Management Team meeting, engineers were cleared to begin loading a half-million gallons of supercold liquid oxygen and hydrogen rocket fuel into Atlantis' external tank at 7:06 a.m. A few minutes later, the engine cutoff - ECO - sensors at the base of the tank were covered with supercold propellant.

The ECO sensors are part of a backup system that ensures the shuttle's three main engines don't drain the tank in the event of other problems during the climb to space that might prevent an on-time shut down.

The ECO sensors can indicate two possible states: wet or dry. If the sensors falsely indicated they are submerged in fuel when, in fact, the tank is dry, the engines could run out of propellant while operating at flight pressures, speeds and temperatures, suffering catastrophic failures.

Based on the logic used in the computer software that monitors the sensors during ascent, two "failed wet" sensors would have no impact. But a third sensor failing wet could trigger a premature engine shutdown to protect against the possibility of the remaining sensor failing in the dry state. Launching with two sensors in the failed wet state would leave no redundancy in the system.

Propellants flow into the tank from the bottom and shortly after the four engine cutoff sensors at the base of the hydrogen section were submerged today, commands were sent to simulate dry conditions to make sure the circuitry responded properly. Voltage readings from two of the sensors immediately indicated a dry state while sensors 3 and 4 showed voltages higher than 13.5 volts, an indication of an open circuit. The readings occurred simultaneously.

"The failure occurred during tanking, 16 minutes into fast fill," Launch Director Doug Lyons said earlier today. "We picked it up while implementing our standard checkout of the system. As soon as we get these sensors wet, we go through a battery of checks to make sure they're operating nominally and properly. We were at a point in the test where we sent commands to take all four sensors dry. When we did that, sensors 1 and 2 went dry as expected and sensors 3 and 4 went wet. And right then, we knew we had an issue."

Because of earlier problems with ECO sensors, NASA developed extensive troubleshooting techniques and ultimately developed an "exception" to a previous launch guideline requiring four operational ECO sensors for a countdown to proceed. Under the exception, a launch could proceed, managers decided, if A) one hydrogen sensor failed wet; and B) engineers could show the problem didn't originate in the multiplexer-demultiplexer avionics system that controls the flow of data to and from the sensors.

As originally written, the flight rule exception called for standing down a day. A second launch try could then be made depending on an analysis of the way the sensor failed and how it behaved during a second fueling. With one sensor failed wet, two more ECO sensors would have to fail wet to pose the threat of running the tank dry. The exception did not cover the case of two failed sensors.

In the wake of the earlier problems, NASA added instrumentation to the ECO sensor system to provide realtime voltage readings that can indicate a sensor failure or change of state. The instrumentation data was implemented for countdown operations during a shuttle flight last August. But NASA has not yet implemented those changes for ascent operations.

"Once we launch, of course, the sensors are indicating wet, because they are wet, and we know that because they're at the bottom of the tank," Cain said. "Part of the challenge has always been that for a failed condition where it's failed to the wet state, where it's going to stay wet after the sensor is uncovered and really should be showing dry, we don't necessarily have any way of knowing that in real time, or we didn't previously have any way of knowing that the sensor could be failed to the wet state. Now we have some instrumentation on this system that gives us voltage measurements that helps us determine if the indication changes state.

"That's data that we have utilized in pre-launch for our launch commit criteria starting with STS-118 and again on STS-120. It's also in place for this mission. We have yet to implement it in real time for the flight operations part, in other words past T-zero where the flight director and mission control team, working with the crew, would do something with that data if it changed in flight and told them that they might have a sensor failed to the wet state. We have previously not done that because we didn't have the data. As I said, the mission operations team and the crews have been working on how to implement this into their thinking and into their flight rules and into their procedures. So they didn't just start thinking about it this morning."

Cain said he has directed the shuttle team to complete preliminary work and make those changes, if possible, in time for a Saturday launch attempt.

"What's currently in the plan is that we'll try to put together an operational workaround plan that we can get comfortable with that will allow us to go fly on Saturday," Cain said. "And it would be with the intent of flying with one or more failures potentially in the system when we go tank up again.

"If the failures of (ECO sensors) 3 and 4 are still there, the intent would be to have rationale that says operationally we can work around this and still drive the crew safety risk down to zero, or as close to zero as we can, and probably accept some additional programmatic risk between the shuttle and the station programs, but be able to do that and still go fly in December."

Programmatic risk in this case means a slightly higher risk of a premature engine shutdown, the result of some other problem in concert with ECO sensor failures, that could result in a trans-Atlantic landing. An emergency landing in Spain or France would cause major disruption to the space station assembly schedule and NASA's plans to complete the outpost and retire the shuttle by 2010.

Engineers say the odds of a premature engine shutdown in this case are acceptably remote because multiple failures would be required - ECO sensor failures as well as a leak or problems elsewhere in the system that would cause the shuttle to use up its hydrogen fuel at a higher-than-expected rate.

But not everyone agrees. Some engineers favor rolling Atlantis back to the Vehicle Assembly Building for repairs. NASA Administrator Mike Griffin participated in today's Mission Management Team meeting and presumably will weigh in on how the agency proceeds this weekend.

11:15 AM, 12/6/07, Update: Launch director hopeful about ECO sensor fix

Engineers troubleshooting the apparent failure of two low-level hydrogen fuel sensors in the shuttle Atlantis' external tank say the problem appears to be the result of an open circuit. Whether that is true or not, and whether the problem requires repairs, is not yet known. While troubleshooting continues, however, the launch team is recycling the countdown to permit a second launch try Friday, at 4:09:13 p.m., to kick off a long-awaited flight to deliver Europe's Columbus research module to the international space station.

"Of course, we're a little disappointed in the events today," said Launch Director Doug Lyons. "But we're certainly working to resolve our issues and make an attempt as soon as we possibly can."

With launch scheduled for 4:31:45 p.m. today, engineers began loading a half-million gallons of supercold liquid oxygen and hydrogen rocket fuel into Atlantis' external tank at 7:06 a.m. Propellants flow into the tank from the bottom and as soon as the four engine cutoff sensors at the base of the hydrogen section were submerged, engineers began a series of tests to confirm they would operate properly in flight.

The ECO sensors are part of a backup system that ensures the shuttle's three main engines don't drain the tank in the event of other problems that might prevent an on-time shut down. The sensors can indicate two possible states: wet or dry.

During today's test, commands were sent to simulate dry conditions to make sure the circuitry responded properly. Voltage readings from two of the sensors immediately indicated a dry state while sensors 3 and 4 showed voltages higher than 13.5 volts, an indication of an open circuit. The readings occurred simultaneously.

"The failure occurred during tanking, 16 minutes into fast fill," Lyons said. "We picked it up while implementing our standard checkout of the system. As soon as we get these sensors wet, we go through a battery of checks to make sure they're operating nominally and properly. We were at a point in the test where we sent commands to take all four sensors dry. When we did that, sensors 1 and 2 went dry as expected and sensors 3 and 4 went wet. And right then, we knew we had an issue.

"We stopped and picked up an interim problem report. We have pre-planned troubleshooting procedures and we put those in place and started working through our troubleshooting and collecting data to try to understand exactly what the situation was and why we were having this problem. So we remained in that configuration and continued tanking and did our troubleshooting and collected all the data we could possibly collect.

"The preliminary indications are we have an open circuit there," Lyons said. "But again, we've got to do some additional engineering analysis and evaluation to see if that is the problem and then more importantly, where that open circuit is, whether it's a connector, a splice line or something of that nature. Once we isolate that, we can determine the appropriate corrective action."

Because of earlier problems with ECO sensors, NASA developed extensive troubleshooting techniques and ultimately seveloped an "exception" to a previous launch guideline requiring four operational ECO sensors. A launch could proceed, managers decided, if A) one hydrogen sensor failed wet; and B) engineers could show the problem didn't originate in the multiplexer-demultiplexer avionics system that controls the flow of data to and from the sensors.

As originally written, the flight rule exception called for standing down a day. A second launch try could then be made depending on an analysis of the way the sensor failed and how it behaved during a second fueling. With one sensor failed wet, two more ECO sensors would have to fail wet to pose the threat of running the tank dry. The exception did not cover the case of two failed sensors.

As for where the problem might be with the sensors aboard Atlantis, Lyons said "there's wiring from the point sensor box (in the engine compartment) that takes the readings, there's wiring in the orbiter aft into the external tank to the sensors."

"The sensors are located inside the LH2 tank and of course, they were functioning when they were installed and checked out," he said. "They've been through checkouts as we've gone through our processing flow from build ... all the way out to the pad. Of course, this is the first time they've seen cryos (cold fuel) so that's certainly something the engineering folks are looking at and may be contributing to this condition."

NASA's Mission Management Team plans to meet at 2 p.m. to discuss the results of troubleshooting and to make a decision about whether to proceed with another launch attempt Friday.

"We want to make sure we preserve the capability to go tomorrow if that's what the technical community determines is the right thing to do," Lyons said. "So we're keeping all our options open."

Atlantis' launch window closes Dec. 13 because of temperature and power issues related to the space station's orbit relative to the sun. The shuttle launch window reopens Dec. 30, but NASA managers have said if Atlantis misses the current window, launch would slip into early January.

Before returning to console to oversee de-tanking operations, Lyons said he was hopeful "we can work our way through this and get a few launch attempts in this window. So we still have hope and reason to believe that we're going to get off in December. That's what we're all shooting (for) and again, we're confident we'll get there."

10:00 AM, 12/6/07, Update: Shuttle launch scrubbed

Today's planned launch of the shuttle Atlantis on a long-awaited mission to carry a European research lab to the international space station has been postponed at least 24 hours because of apparent problems with two of four low-level fuel sensors at the base of the ship's external tank.

The launch team is recycling the countdown for a possible launch attempt Friday at 4:09:13 p.m., but that assumes the problem can be resolved by then. The shuttle's eight-day launch window closes Dec. 13. If Atlantis isn't off the ground by then, the flight will slip into early January.

Today's launch scrub was declared at 9:56 a.m., about three hours after engineers began pumping a half million gallons of supercold liquid oxygen and hydrogen rocket fuel into Atlantis' external tank for a launch attempt at 4:31:45 p.m.

But about two hours into the three-hour fueling process, when the hydrogen section of the tank was about 80 percent full, two of four engine cutoff sensors at the base of the hydrogen tank "failed wet." The sensors are part of a backup system used to ensure the shuttle's three main engines don't run the tank dry if some other problem prevents an on-time shut down.

Hydrogen ECO sensors 3 and 4 dropped off line at the same time, which might indicate some sort of circuitry issue rather than an actual sensor failure. But that remains to be seen. If troubleshooting confirms both sensors have, in fact, failed, launch likely would be delayed beyond the end of the current launch window.

But if a problem can be identified in the circuitry or software associated with the ECO sensor system, it may be possible to press ahead Friday or later in the window if any repairs are required and if the wiring or hardware in question is accessible at the launch pad.

A briefing is expected later this morning and this status report will be updated as soon as possible thereafter.

9:23 AM, 12/6/07, Update: ECO sensor background

Engineers are troubleshooting an apparent problem with two of four engine cutoff sensors in the shuttle Atlantis' hydrogen tank that apparently "failed wet" during fuel loading today, meaning they could falsely indicate the tank still has hydrogen in it at the end of the climb to space when, in fact, it is empty.

Here is a bit of background, taken from our coverage of an earlier shuttle mission, on engine cutoff sensors in the shuttle's external tank:

Twenty four propellant sensors are used in the shuttle's external tank, 12 each in the oxygen and hydrogen sections. Eight are used in each tank to measure the amount of propellant present before launch. Four in each tank, known as engine cutoff - ECO - sensors, are part of a backup system intended to make sure the ship's engines don't run too long, draining the tank dry with potentially catastrophic results, after other problems that might prevent an on-time shutdown.

NASA's original launch commit criteria required three operational ECO sensors for a countdown to proceed. But in the wake of the 1986 Challenger disaster, the LCC was amended to four-of-four because of concerns two sensors could be knocked out by a single failure in an upstream electronic black box known as a multiplexer-demultiplexer. The single-point failure later was corrected, but the four-of-four launch rule remained on the books.

Because of ECO sensor problems going into me first post-Columbia mission, NASA managers ultimately developed an "exception" to the four-of-four rule that would permit a launch if A) one hydrogen sensor failed wet; and B) engineers could show the problem didn't originate in the multiplexer-demultiplexer avionics system that controls the flow of data to and from the sensors.

As originally written, the flight rule exception called for standing down a day. A second launch try could then be made depending on an analysis of the way the sensor failed and how it behaved during a second fueling. With one sensor failed wet, two more ECO sensors would have to fail wet to pose the threat of running the tank dry.

The hydrogen ECO sensors are located at the very bottom of the tank near the entrance to the pipe that carries hydrogen into the shuttle's engine compartment.

Ê The cutoff sensors are armed late in the ascent when a relatively small amount of rocket fuel remains in the tank. Once armed, the shuttle's computer system checks the status of each sensor, which is still immersed in cryogenic propellant, to make sure it is "wet." To protect against a faulty sensor, the first "dry" indication from any one of them is discarded.

During normal operations, the shuttle's flight computers continuously calculate the orbiter's position and velocity, using that data to figure out when the engines should be shut down to achieve the desired target. As a backup, the computers also monitor the ECO sensors as the tank empties to protect against unexpected problems that might affect the performance of the propulsion system.

The shuttle is launched with more fuel than it needs and in normal operation, the ECO sensors would never be "dry" before the normal guidance-based engine shutdown sequence begins. But if a problem does occur, and the engines run longer than expected, two "dry" sensors would trigger an engine shutdown to keep from running the tank dry. As long as at least three sensors indicate "wet," however, fuel is assumed to be in the tank and the engines will keep running.

Once the system is armed, two sensors must fail "dry" to trigger an inadvertent engine shutdown. Before arming, three sensors must fail "dry." If three sensors fail "wet," the engines could run the tank empty.

The odds of such multiple failures are "extremely remote," according to internal NASA documents describing earli er problems. In fact, no cutoff sensors have failed in flight since the sixth shuttle mission in 1983 when the design was changed.

But the consequences of an early or late engine shutdown are extreme. A premature shutdown could prevent a crew from reaching orbit while a late shutdown could result in an engine fire or explosion. Even though the cutoff sensor system is considered a backup to the shuttle's flight computers, NASA wants four operational cutoff sensors in each tank to provide multiple layers of redundancy.

The engine cutoff sensor system has been put to the test only two times in the history of the shuttle program.

During the shuttle Challenger's launching July 29, 1985, on mission STS-51F, a main engine shut down five minutes and 43 seconds after blastoff because of an internal temperature sensor failure. The fuel consumption of the two engines that kept running was affected and the end result was an ECO sensor engine cutoff. The only other such shutdown in shuttle history occurred during launch of mission STS-93, when a hydrogen leak in the coolant tubes making up main engine No. 3's nozzle caused more oxygen to be consumed than expected. In that case, oxygen ECO sensors went "dry," triggering engine shutdown.

In both cases, the shutdowns happened late in the ascents and both shuttle crews were able to complete their missions (Challenger's crew ended up in a lower-than-planned orbit due to the earlier engine shutdown).

Problems with ECO sensors bedeviled NASA during the ramp up to the first post-Columbia mission, prompting one launch scrub and intense analysis. After the flight, engineers traced the problem to a suspect connection between sensors and electrical cables in a specific batch of ECO sensors manufactured in the late 1990s.

9:01 AM, 12/6/07, Update: Engine cutoff sensor issue

With the shuttle Atlantis' external tank 80 percent full, engineers are troubleshooting an apparent problem with two of four engine cutoff sensors at the base of the hydrogen section of the huge tank. Sensors 3 and 4 apparently failed, or dropped off line, at the same time. It's not yet clear whether the issue can be resolved in time to complete fuel loading for a launch attempt today or whether the flight will have to be delayed.

Problems with ECO sensors during the initial post-Columbia missions caused numerous launch delays and extensive troubleshooting. It's not yet clear whether the problem today is a real sensor issue, a problem with the circuit the two sensors in questions are connected to or some other issue.

An updated will be posted as soon as more information is available.

7:20 AM, 12/6/07, Update: Shuttle Atlantis fueled for launch

Working by remote control, engineers began pumping a half-million gallons of supercold liquid oxygen and hydrogen rocket fuel into the shuttle Atlantis' external tank today, setting the stage for a launch attempt 4:31:45 p.m.

The three-hour fueling process began on time at 7:06 a.m., about 50 minutes after crew wakeup. Commander Steve Frick and his crewmates - pilot Alan Poindexter, flight engineer Rex Walheim, Leland Melvin, German astronaut Hans Schlegel, Stan Love and French space station astronaut Leopold Eyharts plan to begin donning their bright-orange pressure suits around 12:16 p.m. and head for the pad to strap in at 12:46 p.m.

The forecast continues to call for a 90 percent chance of good weather and a NASA spokesman said there are no technical problems of any significance.

"We're doing very well," he said. "We started fueling as soon as we came out of the T-minus-six-hour hold at 7:06. The (Mission Management Team) tanking meeting lasted all of 13 minutes. They're not working anything."

LIftoff is timed to coincide roughly with the moment Earth's rotation carries the launch pad into the plane of the space station's orbit. As of late Wednesday, liftoff was targeted for 4:31:45 p.m., but the time could change by a few seconds during a final hold at the T-minus nine-minute mark.

Here is a timeline of the rest of today's countdown (in EST):

EST,,,,,,.....EVENT

07:06 AM......Oxygen (LO2), hydrogen (LH2) transfer line chilldown
07:16 AM......Main propulsion system chill down
07:16 AM......LH2 slow fill
07:46 AM......LO2 slow fill
07:51 AM......Hydrogen engine cutoff sensors go wet
07:56 AM......LO2 fast fill
08:06 AM......LH2 fast fill
10:01 AM......LH2 topping
10:06 AM......LH2 replenish
10:06 AM......LO2 replenish

10:06 AM......Begin 2-hour 30-minute built-in hold (T-minus 3 hours)
10:06 AM......Closeout crew to white room
10:06 AM......External tank in stable replenish mode
10:36 AM......Astronaut support personnel comm checks
10:55 AM......Astronaut crew quarters photo op (recorded)
11:11 AM......Pre-ingress cockpit switch reconfig
11:30 AM......NASA television coverage begins
12:06 PM......Final crew weather briefing
12:16 PM......Crew suit up begins
12:36 PM......Resume countdown (T-minus 3 hours)

12:46 PM......Astronauts depart crew quarters
01:15 PM......Crew arrives at launch pad; cabin ingress begins
02:01 PM......Astronaut comm checks
02:31 PM......Hatch closure
03:11 PM......White room closeout

03:16 PM......Begin 10-minute built-in hold (T-minus 20m)
03:26 PM......NASA test director countdown briefing
03:26 PM......Resume countdown (T-minus 20m)

03:27 PM......Backup flight computer to OPS 1 software
03:31 PM......KSC area clear to launch

03:37 PM......Begin final built-in hold (T-minus 9m)
04:07 PM......NTD launch status verification
04:22:45 PM...Resume countdown (T-minus 9m)

04:24:15 PM...Orbiter access arm retraction
04:26:45 PM...Launch window opens
04:26:45 PM...Hydraulic power system (APU) start
04:26:50 PM...Terminate LO2 replenish
04:27:45 PM...Purge sequence 4 hydraulic test
04:27:45 PM...Inertial measurement units to inertial
04:27:50 PM...Aerosurface hydraulic system test
04:28:15 PM...Main engine steering test
04:28:50 PM...LO2 tank pressurization
04:29:10 PM...Fuel cells to internal reactants
04:29:15 PM...Clear caution-and-warning memory
04:29:45 PM...Crew closes visors
04:29:48 PM...LH2 tank pressurization
04:30:55 PM...Booster joint heater deactivation
04:31:14 PM...Shuttle computers take control of countdown
04:31:24 PM...Booster steering test
04:31:38 PM...Main engine start (T-6.6 seconds)
04:31:45 PM...Booster ignition (LAUNCH)

10:45 AM, 12/5/07, Update: Weather still 90 percent 'go;' countdown proceeding smoothly

Engineers at the Kennedy Space Center are preparing the shuttle Atlantis for fueling and launch Thursday on a long-awaited mission to deliver Europe's Columbus research lab to the international space station.

With forecasters continuing to predict a 90 percent chance of good weather, NASA Test Director Jeff Spaulding told reporters today there are no technical problems at pad 39A that would delay the start of fueling at 7:06 a.m. Thursday. Launch is targeted for around 4:31:44 p.m.

"After lots of hard work and preparation, I'm pleased to report Atlantis and her crew are finally ready to fly with the Columbus module," Spaulding said. "The countdown is going very smoothly, really no issues to report."

Engineers loaded the shuttle's fuel cell system with hydrogen and oxygen late Tuesday, permitting up to three launch attempts in a row, if necessary, while still preserving the option to extend the mission two days to add a fourth spacewalk. The additional spacewalk is wanted for a detailed inspection of a contaminated solar array rotary joint in the space station's main power truss.

But the launch window closes Dec. 13. If Atlantis isn't off the ground by Friday or Saturday, the team will stand down to reload the shuttle's fuel cell system before a final attempt or two at the end of the window.

Spaulding said the fuel cell loading operation went well, but engineers are troubleshooting a small leak in a ground vent system. The issue will have no impact on launch, but if Atlantis is delayed long enough to require a fuel cell "top off" with fresh hydrogen or oxygen, the leak might require repairs.

Earlier, the ground team repaired three small areas of damage to the external tank's protective foam insulation.

The only other problems involve post-Columbia improvements to monitor foam loss from the external tank and to measure possible debris impacts on the ship's wing leading edge panels.

Two issues are affecting external tank documentation. The tank will separate from Atlantis in orbital darkness but even if good lighting was available, a software problem would hinder the crew's ability to downlink whatever pictures might be snapped by a camera mounted in the shuttle's belly. The pictures will be stored on board, however, for post-flight analysis.

A troublesome firmware upgrade to the ship's wing leading edge impact sensor system apparently will prevent any data collection during the climb to space and throughout the mission.

LeRoy Cain, director of shuttle integration at the Kennedy Space Center, said Tuesday it was safe to proceed with launch because the external tank umbilical camera photography and the wing leading edge sensor system are used primarily as backup methods for detecting critical damage to the shuttle's heat shield and foam loss from the external tank.

As always, he said, the crew will carry out detailed heat shield inspections using laser scanners and high-resolution cameras the day after launch and again, after the shuttle undocks from the space station. In addition, the station crew will photograph the shuttle's underbelly during final approach to look for signs of damage, a now-standard part of every post-Columbia mission.

Atlantis commander Steve Frick and his crewmates were briefed on the progress of the countdown early today.

"At this point, I'm pleased to report that all of our launch systems and the launch teams are ready and more importantly, Atlantis and her crew are ready to open a gateway for this newest voyage of Columbus," Spaulding said.

Forecasters, meanwhile, are predicting near ideal weather for Thursday's launch attempt, calling for only a 10 percent chance of low clouds in the area. The odds are 80 percent "go" Friday and 60 percent favorable on Saturday.

"The vehicle's looking good and the weather's looking good, too, both here at Kennedy Space Center and at the TAL (trans-Atlantic landing) sites," said weather officer Kathy WInters.

"We'll have a cold front that's going to be moving through tomorrow morning but it's going to be dry and so we're not expecting any weather with it. So the only thing we have just a slight concern for is if we get any cold air, strato-cumulus clouds that come in from off the water, that would be a low-cloud/ceiling issue. But really, overall we have just a 10 percent chance of KSC weather prohibiting launch."

At least one of NASA's three emergency runways in Spain and France should be acceptable all three days, but the weather at emergency runways in New Mexico and California could be a problem Friday and Saturday, with a chance of showers at both sites.

01:00 PM, 12/3/07, Update: Atlantis crew flies to KSC for start of countdown (UPDATED at 7:05 p.m. with start of countdown)

The crew of the shuttle Atlantis flew to the Kennedy Space Center today for the start of the countdown to blastoff Thursday on a long-awaited mission to attach a European laboratory to the international space station. There are no technical problems of any significance at launch complex 39A and forecasters are predicting an 80 percent chance of good weather.

"We're really excited to be here in Florida today, obviously on a tremendous day, and we hope it stays like this all week long to have our chance to launch in Atlantis on Thursday and bring the Columbus module up to the international space station," commander Steve Frick told reporters at the shuttle runway.

"Obviously, it's been a real long training flow for us, a long time building to this moment and so we're just absolutely ready to go. We know the shuttle program has worked really hard to get Atlantis ready, actually ahead of schedule, for this Thursday and the station folks and Peggy Whitson and her crew up on orbit have worked just tremendous hours the last month, month and a half, to ... get it ready so we could actually launch on time. We only have a week of launch window, so we're really excited to launch successfully on the first try."

The shuttle's countdown began on time at 7 p.m., setting up a launch attempt around 4:31:44 p.m. Thursday. At a morning status briefing, NASA Test Director Charlie Blackwell-Thompson said engineers are repairing three areas of minor damage to foam insulation on the shuttle's external fuel tank but otherwise, Atlantis is in good condition going into its countdown to launch.

"All of our systems are in good shape, our countdown work in on schedule and we have no significant issues to report," she said. "Our teams are ready, Atlantis is ready and we're all looking forward to Thursday's launch."

Shuttle weather officer Kathy Winters said good good conditions are expected Thursday, although there is a 20 percent chance of low clouds in the area depending on how an approaching front behaves later in the week.

"The weather is actually looking pretty good for launch day, we're very optimistic right now about it," Winters said. "The only concern we have is a frontal boundary that's going to be moving through this evening will be down to the south and at some point, it's going to start turning back towards our area. The first thing that occurs when that happens is a ceiling rolls into the area. That's our primary concern for launch.

"But it looks like that would be more likely to happen on Friday. Friday and Saturday, the weather would deteriorate. So the first day, the first attempt on the sixth of December, is the best weather day.

Winters said the forecast for Thursday is 80 percent "go," decreasing to 60 percent go on Friday and Saturday.

The primary goal of the year's fourth shuttle mission is to deliver the European Space Agency's Columbus research module to the international space station. Joining Frick aboard Atlantis will be pilot Alan Poindexter, Leland Melvin, flight engineer and lead spacewalker Rex Walheim, German astronaut Hans Schlegel, Stan Love and French astronaut Leopold Eyharts, who will replace station flight engineer Dan Tani.

"As you probably all know, Columbus is the biggest contribution from Europe for the international space station," Schlegel said today at the shuttle runway . "And from the bottom of my heart, I want to thank all the people in Europe, in the U.S., and all the other international partners who got us here and made Columbus ready for launch. I feel very honored to be a member of this crew that will bring up Columbus for Europe into space.

"By doing this, launching Columbus, attaching it to the international space station, operating it around the clock, Europe will become a senior partner in human space flight. And I'm very glad, I'm very proud to be an active part of this team effort."

Said Eyharts: "It's a great honor for me to be part of this mission, on this shuttle crew and the ISS Expedition 16 crew." Noting that he is not scheduled to return to Earth until the next shuttle flight in late February, "I would like to wish you all a merry Christmas and a happy New Year. See you in 2008."

Three spacewalks are planned to get Columbus installed; to replace a nitrogen tank used to help pressurize the station's ammonia coolant system; to install two European experiments on the outboard bulkhead of the new research lab; and to move a failed control moment gyroscope back to the shuttle for return to Earth.

But flight controllers hope to extend the mission by two days and add a fourth spacewalk if Atlantis has enough on-board hydrogen and oxygen to power the ship's electrical generators. If the shuttle gets off the pad during the first three days of its eight-day launch window, the crew should have enough power to support the mission extension. If the flight is delayed past Dec. 8, launch would slip to the end of the window to give ground crews time to reload hydrogen and oxygen for the shuttle's fuel cell system.

The launch window closes Dec. 13 because of periodic solar power and temperature issues related to the space station's orbit. The launch window reopens Dec. 30, but program managers say if Atlantis isn't off the ground by Dec. 13, the flight will be delayed to early January.

6:43 PM, 11/30/07, Update: Atlantis cleared for Dec. 6 launch

NASA managers today cleared the shuttle Atlantis and its crew for blastoff Dec. 6 on a long-awaited flight to attach the European Space Agency's Columbus research lab to the international space station.

With commander Steve Frick and pilot Alan Poindexter at the controls, Atlantis is scheduled to lift off from pad 39A at the Kennedy Space Center at 4:31:44 p.m. next Thursday, roughly the moment when Earth's rotation carries the launch pad into the plane of the space station's orbit.

"We have had three outstanding flights of the space shuttle so far this year and we're looking forward to a fourth," shuttle Program Manager Wayne Hale told reporters late today. "Atlantis is on the pad, ready to go, no major issues or concerns regarding that vehicle.

"We are looking at Discovery, having just come back from its last mission in almost pristine shape, really good condition. And looking ahead into February, you saw the external tank delivered here today to the Kennedy Space Center (for the next mission) and processing on Endeavour is going very well.

"So all in all, the hard work of a large number of folks is really beginning to pay off," Hale said. "We had a full and frank flight readiness review today, it was a great review, we laid a lot of things out on the table and at the end of the day everyone was comfortable that we're ready to go fly."

NASA will only have a week or so to get Atlantis off the ground before the launch window closes due to temperature constraints related to the station's orbit. If the shuttle isn't off by Dec. 13, the flight will slip to early January.

At the nearby Cape Canaveral Air Force Station, meanwhile, United Launch Alliance is preparing an unmanned Atlas 5 rocket for takeoff Dec. 10 to boost a classified National Reconnaissance Office satellite into orbit. While no final decisions have been made, that flight likely would slip a few days if Atlantis doesn't get off on time to avoid a potential conflict.

Frick, Poindexter, flight engineer Rex Walheim, Leland Melvin, Stan Love and European astronauts Hans Schlegel and Leopold Eyharts, a French air force general, plan to attach the Columbus module to the newly installed Harmony module's right-side port on Dec. 9, the day after docking.

Three spacewalks are planned, two by Walheim and Schlegel and one by Walheim and Love, to connect and outfit Columbus, to replace a nitrogen tank used to pressurize the station's ammonia coolant system and to move a faulty gyroscope back to the shuttle for return to Earth.

In addition to delivering Columbus, Atlantis also will ferry Eyharts to the station. The European Space Agency astronaut, veteran of a three-week stay aboard the Russian Mir space station in 1998, will replace Expedition 16 flight engineer Dan Tani aboard the ISS. Tani will return to Earth in Eyharts' place aboard Atlantis.

"We all come into these space shuttle flights looking at the big element in the payload bay and waiting for the action when we actually install it," said station Program Manager Mike Suffredini. "This flight and the following stage and multiple stages after that will be an extra challenge for us.

"We have been working with our Russian counterparts and our Canadian counterparts for the better part of about seven years and in all that time, we evolved in our operations capability, how we work together. And now we're bringing on another partner, multiple countries, multiple control centers to operate this Columbus module.

"So the very small part you'll see during the docked operations of installing the Columbus module really will just be the tip of the iceberg as we work together in a partnership and move on into the next couple of flights," Suffredini said. "By April, we'll have the (Japanese modules) up and we'll have yet another partner in operation with us. So it's a very exciting time for us in the ISS program."

As it currently stands, Atlantis will land back at the Kennedy Space Center around 12:29 p.m. on Dec. 17. But depending on when Atlantis actually takes off, and how much oxygen and hydrogen are available to power the ship's electricity producing fuel cells, NASA managers may extend the mission by two days and add a fourth spacewalk.

The goal is to conduct an additional inspection of the station's right-side solar array rotary joint to help determine the source of metallic contamination in the mechanism.

The space station is equipped with two solar alpha rotary joints, or SARJs, one on each side of the lab's main power truss. The SARJ joints rotate outboard solar arrays like giant paddle wheels as the station circles the planet, keeping the blankets face-on to the sun to maximize electrical output.

Each joint features two redundant 10-foot-wide gear/race rings and two drive motors, only one of which is engaged at any given time. Twelve so-called trundle bearing assemblies are positioned around one of the two gear races to allow smooth rotary operation.

The left-side SARJ is rotating normally, but earlier this fall flight controllers noticed unusual vibration and slightly higher current levels in the right-side SARJ. Tani, who was ferried to the station aboard the shuttle Discovery last month, looked inside the joint behind thermal panel No. 12 during an already planned spacewalk Oct. 28.

He spotted metallic contamination and collected samples using adhesive tape. Those samples later were determined to be made up of race ring material. At that point, mission managers decided to lock the starboard SARJ in place to prevent additional damage.

During a second inspection by Tani during a spacewalk Nov. 24, additional contamination was spotted. In a worst-case scenario, the 12 bearing assemblies and two drive motors could be moved to the redundant gear during three to four spacewalks. But engineers do not want to consider such a drastic step until they figure out what is causing the problem with the active gear and race ring.

If a fourth spacewalk ultimately is approved for the Atlantis mission - and no such decision will be made until after launch - Love and Tani would carry out a more detailed inspection of the mechanism's drive motor, bearings and the bearing race ring now known to be damaged.

"With some power downs, we can get a couple of extra days," said Suffredini. "So if everything goes well and we get a couple of extra days, we would attempt an EVA 4. And during an EVA 4, we would do a thorough inspection of the entire joint. We would take samples, we would remove many of the (thermal) covers. We'd like to remove them all, we're not sure we can do that in the EVA so we have a priority.

"We'll remove all the covers that will reveal all the trundle bearings, we'll remove the covers that will reveal the drive (motors), we'll inspect that, we'll take samples all the way around, we'll look with a mirror so we can see the under part of the race. And we'll take a number of photographs and then we'll retrieve one of the 12 trundle bearings. We have one selected,Êbut if in our inspections we find one that really stands out we could choose to take that one.

"Our analysis says we can operate the joint on 11 of 12 trundle bearings and we believe that the data we could glean from one of the trundle bearings bringing it home is worth the effort. ... So that's the plan, assuming we can get the extra two days."

Suffredini said the station can safely operate with the right-side SARJ locked in place through launch of two Japanese research modules in February and April. But at some point next spring, NASA needs to get the joint rotating again, either with a repair or using different operating procedures.

Preparing for a variety of possible repair options, Atlantis' crew will carry up a new drive motor. Ten to 12 new trundle bearings will be ferried to the station aboard Endeavour in February.

3:00 PM, 11/10/07, Update: Atlantis hauled to launch pad

The shuttle Atlantis was hauled to launch pad 39A today for work to ready the ship for blastoff Dec. 6 on a long-awaited three-spacewalk mission to deliver and attach a European research lab to the international space station.

The shuttle's crew - commander Steve Frick, pilot Alan Poindexter, Leland Melvin, Rex Walheim, German astronaut Hans Schlegel and French air force Gen. Leopold Eyharts - plan to strap in aboard Atlantis Nov. 20 for a dress-rehearsal countdown.

If all goes well, the real countdown will begin at 7 p.m. on Dec. 3 for a launch attempt around 4:31 p.m. Dec. 6. The primary goal of the 121st shuttle mission is attachment of the European space Agency's Columbus research module to the new Harmony module's right-side port.

Eyharts, representing the European Space Agency, will replace astronaut Dan Tani as a member of the Expedition 16 crew and remain aboard the lab complex when Atlantis departs. Tani, launched to the station Oct. 23 aboard the shuttle Discovery, will take Eyharts' place aboard Atlantis for the return to Earth on Dec. 17.

The launch window for the STS-122 mission closes Dec. 13, when the angle between the sun and the plane of the station's orbit exceeds safety limits for shuttle temperature control when docked to the lab.

While the shuttle team at the Kennedy Space Center expects to have Atlantis ready for takeoff by Dec. 6, it is not yet clear whether the space station program will be ready for Columbus.

ISS-16 commander Peggy Whitson, Yuri Malenchenko and Tani face a busy three weeks of work to move the station's shuttle docking port to the newly installed Harmony module; to move the assembled Harmony stack back to the front of the Destiny laboratory module; and to carry out two spacewalks to connect Harmony to station power and cooling.

The spacewalks are planned for Nov. 20 and 24, following by a space station readiness review Nov. 27. A headquarters-level flight readiness review is scheduled for Nov. 30. Depending on the progress of work this month to prepare the station for Columbus, Atlantis' launch could slip a few days to give the ISS-16 crew more time.

But if Atlantis isn't off by Dec. 13, the flight will be delayed to Jan. 2.

Here is a timeline of major mission events (in EST and mission elapsed time; a detailed flight plan is posted on the CBS News STS-122 Quick-Look page:

DATE/EST.......DD...HH...MM...EVENT

12/06/07
Thu 04:31 PM...00...00...00...STS-122 launch
Thu 10:31 PM...00...06...00...Crew sleep begins

12/07/07
Fri 06:31 AM...00...14...00...Crew wakeup
Fri 11:06 AM...00...18...35...Heat shield inspection
Fri 06:36 PM...01...02...05...Rendezvous tools checkout
Fri 10:31 PM...01...06...00...Crew sleep begins

12/08/07
Sat 06:31 AM...01...14...00...STS/ISS crew wakeup
Sat 12:41 PM...01...20...10...Approach timeline begins
Sat 02:08 PM...01...21...37...DOCKING
Sat 03:16 PM...01...22...45...Hatch opening
Sat 06:06 PM...02...01...35...Inspection boom handoff to shuttle arm
Sat 10:01 PM...02...05...30...ISS crew sleep begins
Sat 10:31 PM...02...06...00...STS crew sleep begin

12/09/07
Sun 06:31 AM...02...14...00...STS/ISS crew wakeup
Sun 11:26 AM...02...18...55...EVA-1: Airlock egress
Sun 03:16 PM...02...22...45...Station arm unberths Columbus
Sun 05:01 PM...03...00...30...Columbus bolted to Harmony
Sun 05:46 PM...03...01...15...EVA-1: Airlock ingress
Sun 10:01 PM...03...05...30...ISS crew sleep begins
Sun 10:31 PM...03...06...00...STS/ISS crew sleep begins

12/10/07
Mon 06:31 AM...03...14...00...STS/ISS crew wakeup
Mon 05:06 PM...04...00...35...Columbus module ingress
Mon 10:01 PM...04...05...30...ISS crew sleep begins
Mon 10:31 PM...04...06...00...STS crew sleep begins

12/11/07
Tue 06:31 AM...04...14...00...STS/ISS crew wakeup
Tue 11:26 AM...04...18...55...EVA-2: Airlock egress
Tue 05:51 PM...05...01...20...EVA-2: Airlock repressurization
Tue 09:01 PM...05...04...30...ISS crew sleep begins
Tue 09:31 PM...05...05...00...STS crew sleep begins

12/12/07
Wed 05:31 AM...05...13...00...STS/ISS crew wakeup
Wed 10:11 AM...05...17...40...ESA PAO event
Wed 10:11 AM...05...17...40...Crew off duty time begins (staggered)
Wed 09:01 PM...06...04...30...ISS crew sleep begins
Wed 09:31 PM...06...05...00...STS crew sleep begins

12/13/07
Thu 05:31 AM...06...13...00...STS/ISS crew wakeup
Thu 10:26 AM...06...17...55...EVA-3: Airlock egress
Thu 04:51 PM...07...00...20...EVA-3: Airlock repressurization
Thu 08:01 PM...07...03...30...ISS crew sleep begins
Thu 08:31 PM...07...04...00...STS crew sleep begins

12/14/07
Fri 04:31 AM...07...12...00...STS/ISS crew wakeup
Fri 12:31 PM...07...20...00...Joint crew news conference
Fri 04:01 PM...07...23...30...Farewell ceremony
Fri 04:16 PM...07...23...45...Hatches closed
Fri 08:01 PM...08...03...30...ISS crew sleep begins
Fri 08:31 PM...08...04...00...STS crew sleep begins

12/15/07
Sat 03:31 AM...08...12...00...STS/ISS crew wakeup
Sat 07:21 AM...08...15...50...Atlantis undocks from space station
Sat 11:11 AM...08...19...40...Post-undocking heat shield inspection
Sat 06:01 PM...09...02...30...ISS crew sleep begins
Sat 07:01 PM...09...03...30...STS crew sleep begins

12/16/07
Sun 03:01 AM...09...11...30...Crew wakeup
Sun 07:01 AM...09...15...30...Flight control system checkout
Sun 02:31 PM...09...23...00...Recumbent seat setup
Sun 03:01 PM...09...23...30...Crew off duty
Sun 07:01 PM...10...03...30...Crew sleep begins

12/17/07
Mon 03:01 AM...10...11...30...Crew wakeup
Mon 09:57 AM...10...18...26...Deorbit ignition (rev. 171)
Mon 11:01 AM...10...19...30...Landing