Hubble piece is cast away from shuttle

Astronauts Kathy Thornton and Tom Akers disconnected a twisted solar array from NASA's Hubble Space Telescope during the Endeavour crew's second of back-to-back spacewalks Sunday and cast the damaged hardware overboard.

Thornton, a slight, 41-year-old physicist on her second career spacewalk, carried the mangled, 350-pound array high above Endeavour as a passenger on the tip of the ship's 50-foot-long robot arm before discarding it.

"It looks like a bird, Tom. Look at it," Thornton said with the release. "Holy moley, piece of cake."

"There it goes," confirmed Akers, as the flat, narrow, metal-and-fabric structure slowly tumbled away.

Thornton conducted her work unable to hear instructions directly from ground controllers because of a bad receiver in her spacesuit. Instead, Akers, a veteran of two previous spacewalks, or astronauts aboard the shuttle relayed ground comments to her.

Swiss astronaut Claude Nicollier operated the shuttle arm from a console inside Endeavour's crew compartment.

Thornton was fastened to the tip of the nimble robot arm by a massive foot clamp. She grasped the mangled array with a handle she fastened to the device.

The space agency elected to discard the solar array, one of two winglike pieces of hardware on the outside of the space telescope that converted sunlight to electrical power, after it failed to fully retract early Sunday.

Replacement of the observatory's old solar arrays, which fluttered severely as the result of a design defect, were among the highest in priority of the 11 repair items on the $700 million Hubble repair mission's agenda.

Thornton and Akers planned to fasten a new pair of the solar generators to the telescope during the remainder of the mission's second lengthy spacewalk overnight.

The shuttle, with the towering four-story telescope secured to a maneuverable workbench in its cargo bay, is circling the Earth at an altitude of about 365 miles and a velocity of nearly 18,000 mph.

Endeavour commander Dick Covey gently maneuvered his ship away from the rogue solar structure as it tumbled gently with Thornton's release.

The discarded fabric-and-metal array should lose altitude and burn up in the Earth's atmosphere within a year, NASA said.

The European Space Agency, which provided a $45 million pair of modified solar arrays for the repair mission, had hoped to regain both of the power generators for engineering analysis.

However, as the Endeavour astronauts rendezvoused with and retrieved the space telescope Saturday, it was apparent the damage might keep the discarded array from being safely returned to Earth in the shuttle's cargo bay.

Its failure to roll up like a window shade in response to ground commands early Sunday confirmed that suspicion.

During the mission's first spacewalk early Sunday, astronauts Story Musgrave and Jeff Hoffman successfully restored the space telescope's failing gyroscopes to full capability, assuring astronomers they will be able to precisely point the observatory at celestial targets for years.

The mission's third and fourth spacewalks, to begin late today and Tuesday, will attempt to correct the infamous flaw in the Hubble's 94-inch-wide primary mirror with the installation of two large components called the Wide Field Planetary Camera II and the Corrective Optics Space Telescope Axial Replacement, or COSTAR.

The mirror flaw was not diagnosed until after the boxcar-size telescope was launched by shuttle astronauts in April 1990.

As Endeavour's crew rendezvoused with the observatory over the weekend, they discovered that one of the two 40-foot-long solar arrays had been permanently twisted by its constant flutter.

The decision by mission managers to cast it away from Endeavour rather than attempt to return it to Earth for an engineering analysis was reached after the first spacewalk, when the array would not retract.

The undistorted companion array retracted perfectly. Electrical motors rolled it up like a window shade.

The only hitch in Sunday's first spacewalk developed when two 7-foot-tall, 4-foot-wide aluminum doors that enclose the closetlike cavity that houses the Hubble's six gyroscopes failed to relatch properly.

Engineers believe the difficulty was caused by a temperature contraction.

Musgrave used a strap and ratchet device from the shuttle's ample tool kit to force the doors into position so its four latches could be closed.