Astronauts to try to wiggle solar panel loose (Reuters)
15.12.2006 03:49 Space - Source: Yahoo space
NASA engineers also worked overnight to correct a problem with the station's attitude control that surfaced after the second spacewalk ended on Thursday.
Early on Friday, astronauts will test whether the previous day's spacewalk jarred loose a jammed solar panel that failed to fully retract during six hours of being furled and unfurled on Wednesday.
The 110-foot (33 meter) panel is part of the station's original power system but had to be retracted to allow room for new solar arrays, installed in September, to rotate and track the sun for power.
The old array, which is supposed to fold up like a window blind, must be fully closed before it can be moved during a shuttle mission next year. It may be blocking access to a space station port set to be used during a Soyuz mission in April.
The panel repeatedly jammed as it was being retracted into a storage box because a tension line on one side of the wing appeared to hang up on a grommet, managers said.
The crew plans to try to "wiggle" the line free by agitating the solar array by moving a nearby gimbal or by having an astronaut bounce on the station's exercise equipment.
Mission controllers discovered during an earlier mission that vigorous use of a bungee bar used in resistance exercises can affect the station's solar arrays.
If those methods are successful, the crew will attempt to reel in the solar array later on Friday, lead flight director John Curry said.
FOURTH SPACEWALK
As a last-ditch effort, managers were considering a fourth spacewalk on Sunday or Monday to fold up the wing manually.
But the location of the panel, far from any handholds and close to electrified components, made a fourth spacewalk less attractive.
"One final thing we are looking at is whether structurally we can clear the (space station) for all the activities that will occur over the next several months ... and approaching it at another time," Mike Suffredini, International Space Station program manager, said on Thursday.
Also on Friday, the crew was scheduled to continue transferring more than 8,000 pounds (3.5 tonnes) of cargo and supplies to the space station from Discovery, and loading Earth-bound cargo onto the shuttle.
The 10-member crew was expected to conduct a media briefing and to enjoy a partial day off as they prepare for what was scheduled to be the final spacewalk of the 12-day mission.
Lead spacewalker Robert Curbeam will team with newly arrived space station crew member Sunita Williams on Saturday in an outing to finish rewiring the station.
The rewiring, which taps into the new solar arrays, is a critical step in NASA's plan to add new modules to the $100 billion outpost next year.
The mission's second spacewalk went flawlessly, allowing Curbeam and Christer Fuglesang, Sweden's first astronaut, to finish rewiring half of the station an hour early.
Discovery arrived at the space station on Saturday for a week-long stay. It is scheduled to land at the Kennedy Space Center in Florida on December 21.
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