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updated 4/23/2004 9:45:53 PM ET 2004-04-24T01:45:53

The new crew aboard the International Space Station (ISS) will have to perform an unplanned spacewalk in order to fix a faulty device that powers part of the vehicle's motion control system, NASA announced today.

The problem cropped up Wednesday evening, less than a day after the Expedition 9 crew -- cosmonaut Gennady Padalka and astronaut Michael Fincke -- and European Space Agency astronaut Andre Kuipers, arrived at the space station.

"We are not dealing with a safety issue," said Mike Suffredini, NASA's space station operations manager.

At 4:18:04 p.m. EDT (2018:04 GMT) Wednesday NASA space station controllers received an alarm reporting a failure in a gyroscope responsible for ISS orientation. They tracked the glitch to a failed circuit within the gyroscope's remote power control unit, which serves as both power plug and circuit breaker for the device.

The malfunction cut off power to one of three functioning gyroscopes functioning on the space station, though only two working devices are needed to control the ISS at any given time. Should another fail, the station would have to rely on Russian-built thrusters that use propellant to keep ISS in the proper flight position.

"The biggest risk is that in the next failure will cause us to use propellant," Suffredini said, adding that the glitch has not impacted any activities aboard the ISS. "We have six months to a year of propellant onboard the station."

But the faulty power control unit must eventually be replaced during an unplanned two-person spacewalk, preferably before an upcoming Progress supply ship arrives at the station, he added.

The spacewalk could take up to four hours for the Expedition 9 crew, which already has two scheduled extravehicular activities (EVAs) planned for their mission.

Sufferdini said ISS controllers rejected a plan to conduct the extra spacewalk while Kuipers and Expedition 8 crewmembers Michael Foale and Alexander Kaleri were still docked at the station. The three spacefarers are scheduled to return to Earth on April 29.

"I don't believe it's worth the risk of rushing an EVA and potentially missing something important," Suffredini said.

The Soyuz TMA-3 spacecraft to be used by Expedition 8 and Kuipers for their landing is nearing the end of its certified flight status. Including the spacewalk into the docked timeline would also extend the time Expedition 8 and Kuipers are aboard by up to 10 days and any delay in their return pushes their dawn arrival on Earth into darkness, making recovery more difficult for ground crews.

The space station was originally equipped with four gyroscopes to periodically reposition the station during flight, with the extras serving as a redundancy system.

In 2002, one of the gyroscopes failed outright. Another gyroscope developed a vibration last year that perplexed mission controllers enough to rely on the Russian-built motion control system, which uses jets to change the station's position, for major orbital maneuvers. That gyroscope, however, is now in working order and one of the two still functioning aboard the ISS.

Padalka, Fincke and Kuipers arrived at the space station early Wednesday morning after a successfully docking their Soyuz spacecraft with the orbital outpost.

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