By Anne Walters and Chris Cermak Dec 14, 2006, 3:05 GMT
Washington - Astronauts began rotating a new set of solar panels on the International Space Station Thursday morning, the latest phase in an attempt to hook up a permanent electricity- generating system for the ISS.
In this image released by NASA TV on Tuesday 12 December 2006, European Space Agency (ESA) astronaut Christer Fuglesang (TOP) walks along the P5 Truss segment during the positioning of the truss. EPA/NASA TV
The decision came after the crew encountered difficulties Wednesday with a complicated mechanical process of folding up an old solar panel that has helped power the station for more than six years.
The folding of the 35-metre-long array, as well as the latest rotation, was to clear the way for two spacewalks later this week, but like folding a well-worn map, it was difficult to get it just right, and kinks in the panel kept causing astronauts to try again.
The retraction of the left wing of a solar array began around 1828 GMT Wednesday, and the ISS crew gave up about six hours later as it had retracted just enough to allow them to start the rotation of the new set of solar panels, which were installed during a previous shuttle mission in September.
NASA officials said they were happy the panel had folded enough for them to get on with their work, and were unsure whether another attempt would be made later in space shuttle Discovery's mission to the ISS.
At 0100 GMT Thursday, astronauts began to activate a rotating joint that should allow the 73-metre-long new solar panels on another part of the station to follow the sun while the ISS moves through space.
The folding of the old solar panel and the rotation of the new panels should set the stage for Discovery astronauts to rewire the station's power system, replacing a temporary power system operating since the space station went into orbit in 1998. Spacewalks are planned for late Thursday and Saturday to rewire both halves of the station.
After years of exposure in space, scientists had questioned whether the old lightweight array would return to its original, compact shape. Astronauts had to stop and start the process several times, dragging out the project beyond the anticipated end time.
The astronauts had to reextend the wing dozens of times to get rid of wrinkles that developed in the folding process and were keeping it from collapsing properly.
The panel did not have to fold completely to allow the other panel to rotate, and astronauts were able to retract it by the necessary 40 per cent - but not much further.
NASA has described Discovery's rewiring mission at the ISS as one of the most complex and difficult in the history of space flight.
Discovery lifted off late Saturday from the Kennedy Space Centre at Cape Canaveral, Florida for the construction mission to the ISS.
Discovery is on the second working shuttle mission to the ISS since NASA returned to flight in summer 2005, after the shuttle fleet was grounded for two years following the 2003 Shuttle Columbia disaster, which killed all seven crew members.
NASA spent most of the last year testing new safety systems. The September flight by the Shuttle Atlantis marked the resumption of ISS construction.
The first spacewalk to install a new component on the ISS was completed successfully late Tuesday (early Wednesday GMT).
At a press conference Tuesday, NASA officials said the shuttle's heat shield was cleared for a return flight to Earth and had not been damaged by a micrometeoroid.
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