Spy Satellites Among Assets Used To Eyeball Station

Remember that strange noise heard by Astronaut Michael Foale and Cosmonaut Alexander Kaleri aboard the International Space Station not long ago? Whatever it was, NASA is now relatively comfortable that there was no damage to the station.

It sounded something like a tin can being crunched up. While it was quickly determined that the sound wasn't related to a collision in space, the question remains -- just what was it?

"We haven't seen anything off nominal" that might be related, said Bill Gerstenmaier, NASA's ISS program manager, but the station's management team wants to make certain it understands the problem. Foale and Kaleri used the station's robot arm with cameras to give the station a once-over. They found nothing conclusive. NASA admits, however, that the arm-camera rig can't get a complete view of the station.

So NASA enlisted help that was first offered -- and turned down -- in the case of the doomed shuttle Columbia: spy satellites. Their powerful cameras are raking the station in hopes of finding the cause of the strange noise, but have so far found nothing. But the noise is further justification for a spacewalk both NASA and Russia's space agency are contemplating for February. Both astronauts would be outside the station for several hours. That worries some experts, who worry about contingencies should an emergency arise while both Foale and Kaleri are outside.

There is another problem.

The station's steering controls are now relegated to the Russian thrusters after a problem has cropped up in the gyro-steering system. One of the station's four gyroscopes, which spin at 6,600 rpm, failed last year. About a month ago, engineers on the ground detected faults in the Number 3 gyro.

"It's not where we want to be," but there is enough backup capability with the Russian thrusters that "we're not in any kind of real crisis," said Gerstenmaier, in a televised news conference from Houston on Friday. Still, the questionable gyro leaves the ISS with no room for error. It's designed to work with as few as two of the gyros and now, there are only two left.

FMI: http://spaceflight.nasa.gov/station