Astronauts leave space station for repair work
By Irene Klotz
CAPE CANAVERAL, Florida (Reuters) - Two U.S. astronauts serving aboard the International Space Station floated outside the complex early on Wednesday to begin a spacewalk considered critical to the growth of the outpost.
It was the fifth spacewalk commander Peggy Whitson, a 47-year-old biochemist, has made since arriving at the station in October, and the fourth for flight engineer Dan Tani, who arrived two weeks after Whitson during the last space shuttle mission.
Tani was due to go home in December aboard shuttle Atlantis. That flight, however, was postponed because of problems with a fuel sensor system. The faulty equipment was replaced and NASA managers planned to meet at the Kennedy Space Center in Florida on Wednesday to decide whether to attempt liftoff on February 7.
The shuttle will be carrying Europe's first permanent space laboratory, a bus-sized module named Columbus, which is to be connected to the seven-room complex. NASA plans to follow Columbus' launch with the first part of Japan's Kibo laboratory complex in March.
Before the Japanese components can be installed, NASA must recover part of the station's troubled solar power system. One side of the station's two solar power wings has been locked in place since December, producing a fraction of the power needed to support expanded station operations.
Whitson and Tani will attempt to replace a 200-pound motor that should restore partial mobility, allowing the wing to pivot its panels to catch the sun's rays. The two left the station's airlock shortly before 5 a.m. EST/1000 GMT.
A more complicated repair that will allow the wing to freely rotate like a Ferris wheel is still in the planning stages, said Kirk Shireman, NASA's deputy space station program manager.
While installing the motor, Whitson and Tani will work only during night-time passes around Earth when the solar energy-collecting cells are passive to avoid electrical shock. The station circles Earth about every 90 minutes, half the time in darkness and half in daylight.
NASA is about 60 percent finished building the $100 billion station and has until September 30, 2010, to finish 12 remaining construction and resupply flights before the shuttle fleet is retired. The agency also plans to fly a final servicing call to the Hubble Space Telescope.
(Editing by Doina Chiacu)