Astronauts aboard the International Space Station (ISS) are preparing for a potential spacewalk this month to replace a broken motor at the base of one of their orbital lab's expansive solar wings.
Station commander Peggy Whitson and flight engineer Dan Tani could make the repair as early as late January, but that plan depends on when NASA's space shuttle Atlantis launches toward the ISS with a new European laboratory, NASA officials have said.
"We'll just keep getting ready," Mike Suffredini, NASA's space station program manager, told reporters late Thursday. "And then as we get close to the time for the actual [spacewalk] we'll see where our shuttle friends are."
Atlantis and its STS-122 astronaut crew are currently slated to launch no earlier than Jan.24 on an 11-day construction mission to deliver the European Space Agency's Columbus laboratory to the ISS. The mission has been delayed since early December by glitches with a fuel gauge sensor system in the shuttle's 15-story external tank. Engineers are replacing a suspect electrical connector and hope to ready Atlantis for launch later this month or, more likely, the first week of February.
"If it does turn out that STS-122 can be launched in January, a spacewalk to replace the [solar array motor] would be postponed until after the shuttle mission," NASA spokesperson Pat Ryan said Friday during daily ISS mission commentary.
Suffredini said that while the current glitch, as well as the contamination of a large ISS gear that rotates both of the station's starboard solar arrays like a paddlewheel to continuously face the sun, have impacted the station's electricity-generating abilities, the outpost has enough power supplies to wait until after Atlantis' flight to perform the motor replacement.
At the heart of the planned spacewalk repair is a motor driving a beta gimbal joint that tilts one of the station's two starboard solar wings towards the sun to help maximize power production. The joint suffered a series of electrical shorts last month, prompting Tani and Whitson to inspect its power and data cables for micrometeorite damage during a Dec. 18 spacewalk. When the inspection found no obvious signs of damage, engineers began to suspect the joint's motor — known as a Bearing Motor Roll Ring Module.
The two U.S. astronauts retrieved a spare beta gimbal joint motor from storage inside the ISS on Wednesday to prepare it for the eventual repair.
Tani, who arrived at the ISS in late October, has been trained for the solar array motor replacement. But he is scheduled to return to Earth with the STS-122 crew aboard Atlantis, which will ferry his replacement — French astronaut Leopold Eyharts, of the ESA — to the ISS.
If the solar array motor spacewalk occurs after the upcoming shuttle flight, ISS flight engineer and Russian cosmonaut Yuri Malenchenko will fill in for Tani and accompany Whitson on the repair job, NASA officials said. The spacewalk will mark the fifth of the station's current Expedition 16 mission.
