Hubble Repair Poses Daunting Challenge

Atlantis' astronauts headed out for another spacewalk Friday, this time to give the Hubble Space Telescope some new, badly-needed gyroscopes and batteries.

Astronaut Michael Massimino and fellow spacewalker Michael "Bueno" Good successfully installed four state-of-the-art gyroscopes in the Hubble Space Telescope today, reports CBS News space consultant Bill Harwood.

Replacing Hubble's gyroscopes was the top priority for this final repair mission to the 19-year-old observatory. The gyroscopes are part of the telescope pointing system, and half of the old ones were broken.

Massimino and Good floated out of the shuttle at 8:49 a.m. ET on a spacewalk expected to last about six and a half hours.

Massimino slowly wedged himself into the telescope, head first, and started pulling out the old gyroscopes and putting in the new ones. His spacewalking partner helped.

"Trained my whole life for this," Massimino said as he squeezed his tall, husky body inside. Earlier, outside the telescope, he joked, "Anybody home?"

Replacing the gyro packages requires an astronaut to float inside the telescope, within inches of delicate equipment that could be damaged by an inadvertent movement.

Massimino, a returning Hubble mechanic who is over 6-feet tall, took care not to bump anything inside Hubble while replacing the gyroscopes. Despite the tight fit, NASA expected the work to be relatively straightforward; two gyroscopes are bundled together, for a total of three compact, 24-pound boxes. Sure enough, the first set went in easily.

But an alignment problem prevented installation of a box containing the final two gyros, and the astronauts were forced to install a refurbished spare in its place, Harwood said.

Engineers at the Goddard Space Flight Center in Greenbelt, Md., verified that all six gyros were properly connected and working properly.

Massimino had a brief fright when his communication system fouled up. For a minute or two, no one could not hear him. "That was scary," said one of the astronauts inside when the problem cleared up.

"A little bit," Massimino replied.

The two will also begin replacing battery modules on the telescope.

CBS News space consultant Bill Harwood reports that the telescope's aging nickel-hydrogen batteries now operate at half their original capacity.

"They were built a couple of years before we launched in '90," said Hubble Program Manager Preston Burch. "We're so far beyond the design lifetime it's anybody's guess as to how long they could continue to go. We know it's not infinite. So our best judgment is we should go ahead and still change them out."

It was the second spacewalk in as many days for the Atlantis astronauts. On Thursday, another two-man team installed a powerful new camera and a computer data unit, after struggling with a stubborn bolt. NASA hoped for an easier, less stressful spacewalk Friday.

In all, five spacewalks are planned so that the observatory - beloved by astronomers and many others for its breathtaking views of the universe - is at its apex while living out its remaining years.

Also this morning, astronaut Megan McArthur is using the shuttle's robotic arm to complete an imaging survey, inspecting some tiles on the craft's underbelly that were missed previously.

NASA sweated a few bullets during yesterday's spacewalk, but was very pleased with the results. Astronauts on Thursday swapped out a nearly 16-year-old camera for a new one the size of a baby grand piano.

Once Astronaut Andrew Feustel and John Grunsfeld left the payload bay hatch and got positioned, they ran into a bit of trouble removing the old Wide Field Camera because a bolt was stuck. They fetched extra tools, but none seemed to work.

They were finally urged by Mission Control to use as much force as possible, even though there was a risk the bolt might break. If that had happened, the old camera would be stuck inside, leaving no room for its improved replacement.

"There were tense moments during that activity," Hubble senior scientist David Leckrone said during a post-spacewalk press conference. "I don't normally reveal my age, and I'm not going to here, but I can tell you I'm five years older now than I was when I came into work this morning."

Harwood reports that early Friday, flight controllers informed the astronauts that the newly installed $132 million Wide Field Camera 3 had passed an overnight functional test.

"That's great news," Massimino said.

Grunsfeld and Feustel also completed other major chores, including replacing a science data-handling unit that broke last autumn, and hooking up a docking ring so a robotic craft can guide Hubble into the Pacific Ocean years from now.

But the mission - a last chance to repair the Hubble Space Telescope - is just getting started.

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