Jammed solar panel to be pitched into space



SPACE CENTER, Houston (AP)—NASA decided Sunday to turn one of the Hubble Space Telescope’s troublesome solar wings into instant space junk by simply dumping it overboard during an overnight space walk.

For the mission’s first spacewalk early Sunday by the fix-it crew of the shuttle Endeavour, the verdict was ‘‘we got everything accomplished.’‘

Story Musgrave and Jeff Hoffman spent nearly eight hours in the open cargo bay. When they left, the space telescope had six working gyroscopes again to guide it, three electronics units to run the gyros, and a new set of eight fuses.

‘‘Jeff and Story today have definitely earned their Dr. Goodwrench certificate and service station Endeavour has qualified for a triple A rating,’‘ said David Leckrone, a Hubble program scientist.

The task of installing a new planetary camera and corrective lenses for the Hubble’s other instruments was still ahead. But the mission’s second spacewalk, beginning late Sunday, was reserved for replacing the telescope’s twin solar panels.

‘‘We’re ready for EVA two,’‘ shuttle commander Richard Covey, using the NASA acronym for spacewalks, said after the crew awoke Sunday night. ‘‘The epic continues.’‘

The 40-foot-long panels have provided reliable electricity for the telescope, but they caused a vexing vibration.

One of the panels responded to a ground command to roll up tight like a window shade for transport back to Earth. But the second panel, badly bent out of shape, stuck with 70 percent of it still unrolled. Mission Control decided Sunday to get rid of it after it is removed from the telescope early Monday.

Lead flight director Milt Heflin said spacewalker Kathryn C. Thornton would hold the panel up high over the cargo bay and conduct ‘‘a gentle jettison procedure.’‘

‘‘She’s just going to let go of it,’‘ Heflin said. ‘‘It’s going to stay right there. There will be no pushing.’‘

Shuttle commander Richard Covey planned to fire a small burst from the ship’s smallest jets to move the ship away from the panel, leaving it one of 6,700 pieces of space junk tracked by the North American Aerospace Command.

It was expected to slowly drop into the atmosphere and burn up, a process that might take a year.

Each day’s activities begin just when prime television time is over, unfortunate timing for NASA because the action beamed from 360 miles above Earth in space is dramatic.

The first of the mission’s five spacewalks, the second longest by American astronauts, lasted 7 hours, 54 minutes beginning late Saturday. Musgrave and Hoffman successfully completed their assigned tasks but not without some difficulties.

With practiced ease, they replaced two of three pairs of gyroscopes, two of three electrical units to guide those gyros and exchanged eight main fuses.

But when they tried to close a 7-foot-high access door, its four latches would not meet. The door, one of a set of double doors, must close tightly to protect sensitive star trackers from unwanted light.

It took two hours of pulling and tugging by Musgrave and Hoffman before the doors would close.

Ken Ledbetter, the telescope’s program manager, said the misalignment was caused because the light metal doors were warmed by different amounts of sunlight when they were open and expanded at different rates. The astronauts were told to close them for one orbit and the latches’ position matched again.

On Tuesday, the astronauts are to install the new planetary camera, on Wednesday it is corrective optics for other instruments on the telescope, and on Thursday more electronics will be replaced.

The solar arrays are gold-colored, flexible plastic blankets—wings that extend from each side of the telescope. They convert energy from the sun into electricity to power the telescope’s instruments.

In 1990, shortly after NASA discovered that the telescope’s main mirror had the wrong shape to focus accurately, the panels developed a slight shaking each time they cross from sunlight to darkness and vice versa—a sudden temperature change of 200 degrees 32 times a day.

The frames around the arrays did not accommodate the expansion and contraction caused by the cooling and heating cycles. Engineers blamed that failure for a kink in a supporting stem that caused the array to twist and bend, making it impossible to be rolled up.

Engineers developed computer software to counteract the jitter but that solution absorbed too much computer memory.

The new arrays, built—like the old ones—by the European Space Agency, work with springs that should not be subject to the same contraction and expansion, experts said.