The panel is badly twisted after three years in space - a complication spotted only as the shuttle Endeavour and Hubble came close on Saturday. The crew had tried to roll it up, hoping to bring it back to Earth for tests, but the winding mechanism jammed at the kink.
Over Saturday night two astronauts completed a successful first spacewalk. They fitted new gyroscopes, used to point Hubble in the right direction. The walk took two hours longer than planned, at 7hrs 54mins, because the pair had trouble shutting the telescope's doors.
The fresh gyroscopes are working well, to the delight of mission control. That was a key goal, since Nasa had feared it would lose control of the telescope after three of its six gyroscopes failed.
The astronauts work while Britain is asleep. Last night, Kathy Thornton planned to grab the crippled panel while standing at the end of Endeavour's 50ft robot arm. She would simply let go of the panel, which should drift away, circling Earth for a year before burning up on re-entering the atmosphere. The astronauts hope to fit two more stable solar panels - used to provide Hubble's power. The old ones shook the telescope as they expanded and contracted with temperature changes caused by sunlight.
Tonight, during their third spacewalk, the astronauts hope to replace the wide field and planetary camera, which sends back panoramic views of the stars.
The mission's climax comes tomorrow night, when the astronauts will fit the Costar (Corrective Optics Space Telescope Axial Replacement) to the main telescope. The unit, the size of a telephone box, constitutes the 'spectacles' Nasa hopes will correct Hubble's blurred vision.
The last spacewalk, for minor maintenance, takes place on Wednesday night, and Hubble should be released into orbit on Thursday night. The shuttle's return to Earth is scheduled for next Monday morning.
It will be known if Hubble can see properly only when the first new images are available after six to ten weeks.
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