On The Trail With The Nuke Hunters

President-elect Barack Obama takes the oath of office in 57 days. And security, of course, will be extremely tight. CBS News justice and homeland security correspondent Bob Orr got an exclusive look at how the government prepares for any potential threat.

From the skies over Washington, a super-secret government team is training for the ultimate terrorist threat.

"The closer we are to the ground, the closer we are to the radiation, the better we can see it," said a nuclear scientist. For security, the faces and names of the secret nuke hunters could not be shown on television or revealed.

But CBS News rode along for an exclusive look at a drill aimed at finding stolen radioactive cesium - a potential ingredient for a dirty bomb.

"I've got elevated counts … mark," said a nuclear technician.

A spike on a radiation monitor signals the chopper is zeroing in on the radioactive source.

"So that tells you, 'this is not normal,' this is something that should not be there?" Orr asked the nuclear technician.

"What that says to me is that I have a radioactive isotope emitting energy," he said. "This is more than likely where the source is."

But, in big cities like Washington, where millions of people will gather for January's presidential inauguration, nukes and dirty explosives laced with radiation could be difficult to detect.

That's because "naturally occurring" radiation is everywhere, given off by the granite from U.S. government buildings and the tombstones at Arlington National Cemetery, for example. Even heavily fertilized suburban golf courses emit radiation.

"It's important to establish a baseline of what radiation is there already, so in cases that there is an incident that we won't be let astray by anomalies," the nuclear scientist said.

So far, the team has made radiation maps of the nation's top-two terror targets: Washington and New York. Chicago is next.

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Check out extra footage from Bob Orr's exclusive reporting.

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On the ground, they trained with an alert from a parked car.

Mobile nuke-detectors from the National Nuclear Security Administration are a key part of security at big events like the Super Bowl and the inauguration, where undercover teams will be moving unnoticed among the crowds, quietly snooping for radiation.

"We'll have people walking around with various detectors and devices," said Tom D'Agostino, of the National Nuclear Security Administration. "They'll come up to people, they'll look for anything unusual."

Skeptics downplay the risk of terrorist nukes. But, the consequences of a terrorist nuclear attack are unthinkable.

So these nuke-hunters can't afford to stop looking for the nuclear threat.