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HOUSTON – Two spacewalking astronauts added a new piece to the metal backbone of the International Space Station on Tuesday, clearing the way for a critical power rewiring later this week. Space shuttle Discovery crew members Robert Curbeam, who was making his fourth spacewalk, and partner Christer Fuglesang, a rookie flier and Sweden’s first astronaut, slipped outside the station’s airlock at 3:31 p.m. EDT (2031 GMT) to begin about six hours of work.
Curbeam and Fuglesang guided robot arm operator Joan Higginbotham, who was nudging an 11-foot (3.3-meter) beam into position from aboard the space station. The beam is a connecting piece that will act as a spacer between two power modules.
“This is going to be really slow motion,” Higginbotham said, as she prepared to move the two-tonne segment. “Keep coming, keep coming,” Curbeam called out. Clearance was as tight as 2 inches as Higginbotham delicately maneuvered the new piece into position at the end of the solar array truss, which was delivered to the station in September.
It took a couple of tweaks to properly align all four corners of the beam so it could be bolted into place. During the maneuver, flight controllers told the crew that Discovery’s heat shield had passed all inspections and no additional surveys would be needed. NASA has been meticulous about scouting the shuttle for damage since losing Columbia and seven astronauts in 2003 because of a debris strike. “That’s outstanding news,” said shuttle commander Mark Polansky. “We’re happy to hear that we can go on with normal (station) assembly tomorrow.”
On Wednesday, one of the station’s two 6-year-old solar arrays, which have been the sole power providers to the U.S. sections of the station, is to be folded up. Next year, the second panel will be retracted and the entire power module relocated to boost the station’s power supply. The Discovery crew hopes to leave the station drawing power from the new set of solar arrays delivered and installed during a shuttle mission in September. The rewiring, which is needed to power new laboratories due to arrive next year, is scheduled to be done during spacewalks on Thursday and Saturday. Retracting the old array may be tricky. NASA originally planned to do the work in 2003, but station construction was halted due to the Columbia accident.
Discovery’s flight is the second since the accident dedicated to station assembly. NASA plans at least 13 more missions to complete the station before the shuttle fleet is retired in 2010.
If the array fails to fold up automatically, NASA might dispatch Discovery’s spacewalkers on an extra outing to manually retract the panel. It must be retracted at least 40 percent to leave room for the new arrays to rotate as they track the sun for power.
“Hopefully that will work according to plan,” Polansky said.