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.
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