To complete the day's preparations, Whitson and Tani are "camping out" overnight in the Quest airlock. This procedure protects against decompression sickness as they go to the even lower pressure of spacesuits on Wednesday.

Most of Wednesday's spacewalk will focus on replacement of a motor, called the Bearing Motor Roll Ring Module, which drives the starboard solar wings as they tilt along their axis to follow the sun for optimal power generation as the station orbits the Earth.

The spacewalk is slated to begin at 5:20 a.m. EST. Live coverage on NASA TV kicks off at 4 a.m.

Also on Tuesday, Flight Engineer Yuri Malenchenko completed a repress of the station's oxygen from the supply aboard the docked Progress 27 cargo craft. That Progress vehicle will undock from the station Feb. 4 to make way for the arrival of Progress 28 and its cargo of food, supplies and oxygen on Feb 7.

Spacewalkers to Replace Solar Wing Motor
Expedition 16 Commander Peggy Whitson and Flight Engineer Dan Tani will replace a motor at the base of one of the International Space Station's solar wings during a 6.5-hour spacewalk scheduled to begin early Wednesday.

Whitson will wear the spacesuit with red stripes as the lead spacewalker, while Tani will wear the spacesuit with broken stripes. They are to leave the station's Quest airlock at about 5:20 a.m. EST, though the spacewalk could begin earlier. NASA Television coverage will begin at 4 a.m.

Most of the spacewalk will focus on replacement of the motor, called the Bearing Motor Roll Ring Module (BMRRM). Called the 'broom," the motor drives the starboard solar wings as they tilt along their axis to follow the sun for optimal power generation as the station orbits the Earth.

Major activities of the BMRRM replacement will take place during the night part of the orbit, when less voltage is generated by the solar wings than when they are exposed to the sun. The replacement BMRRM was retrieved from its stowage place in Pressurized Mating Adapter-3 early this month in preparation for the spacewalk.

The motor is part of the Beta Gimbal Assembly, which experienced electrical failures Dec. 8. The removal and replacement of the BMRRM is expected to take about four hours, including pauses during the daylight part of the orbit.

A second major task of the spacewalk is inspection of the starboard Solar Alpha Rotary Joint (SARJ). That device causes the starboard solar wings to rotate in a paddlewheel-like motion to keep the arrays pointed toward the sun.

Previous inspections revealed contamination and debris inside that joint.

Station Flight Engineer Yuri Malenchenko will help the crew with suiting up and provide other support. Astronaut Tom Marshburn will be the ground intravehicular officer. He will be in the station flight control room in Houston's Mission Control acting as spacewalk choreographer.

After cleanup the spacewalkers will re-enter the Quest airlock and close its hatch. The beginning of repressurization marks the official end of the spacewalk.

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