Two US astronauts replaced a broken motor on one of the International Space Station鈥檚 solar wings during a spacewalk on Wednesday, clearing the way for more modules to be added to the outpost.
鈥淭hanks for making it look so easy,鈥� astronaut Tom Marshburn from NASA鈥檚 Mission Control Center in Houston, Texas, US, radioed to the crew as they returned to the station鈥檚 airlock after the seven-hour outing.
It was the fifth spacewalk that 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, 46, who arrived two weeks after Whitson during the last space shuttle mission.
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Tani had been due to go home in December aboard the shuttle Atlantis. But that flight was postponed because of problems with a fuel sensor system. The faulty equipment was replaced and NASA managers were meeting at the Kennedy Space Center in Florida on Wednesday to decide whether to attempt lift-off on 7 February.
The shuttle will carry Europe鈥檚 first permanent space station laboratory, a bus-sized module named Columbus, which is to be connected to the seven-room complex. NASA plans to follow Columbus鈥檚 launch with one carrying the first part of Japan鈥檚 Kibo laboratory complex in March.
Electrical shock
Before the Japanese components can be installed, NASA needed to recover at least part of the station鈥檚 troubled solar power system. One side of the station鈥檚 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 replaced a 90-kg (200-pound) motor that allowed the wing to pivot its panels to catch the Sun鈥檚 rays.
A more complicated repair that will allow the wing to freely rotate like a Ferris wheel is in the planning stages, said Kirk Shireman, NASA鈥檚 deputy space station programme manager.
Whitson and Tani left the station鈥檚 airlock shortly before 1000 GMT. While installing the motor, they worked 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% finished building the $100 billion station and has until 30 September 2010 to finish 12 remaining construction and re-supply flights before the shuttle fleet is retired. The agency also plans to make a final servicing call to the Hubble Space Telescope.
