Problems plague first opening of Hubble telescope in space

Starlight flooded the Hubble Space Telescope's giant mirror for the first time Friday, but control and communications troubles with the $1.55 billion observatory marred the achievement.

After an exchange of handshakes and assurances from ground controllers that they could not solve the Hubble's ills, the Discovery astronauts maneuvered away from the space telescope and prepared to come home.

The astronauts left behind an orbiting Hubble late Friday that had been unexpectedly immobilized by automatic commands from the telescope's on-board computer.

The computer issued the commands earlier in the day after sensing damage to a crucial communications antenna and later experiencing rapid motion triggered by the opening of the observatory's giant lens cover. The automatic "safe mode" commands are designed to prevent the 12-ton observatory from facing into the sun and damaging its sensitive optics.

"What we are really seeing here is that these mechanisms are all behaving a little differently then we could predict," NASA's Mike Harrington said at the Space Telescope Operations Control Center at Greenbelt, Md.

"We weren't able to predict how they would react to Zero G,"said Harrington, referring to the weightlessness of space.

Jean Oliver, the Hubble's deputy project manager, estimated it would take at least a day to coax the telescope out of the safe mode.

And it could take another two days to switch on the observatory's scientific instruments.

Plans to snap the Hubble's first images of the cosmos by the middle of next week face certain delay.

"I'd guess we're at least a week away," said Oliver, characterizing the estimate as an optimistic rough guess.

"I'll probably be proven wrong later," he said.

Friday began with great anticipation that the Hubble's lens cover, or aperture door, would swing open at 6:35 a.m., Houston time.

But ground commands intended to put the Hubble through a series of three maneuvers stressed one of two antennas on the telescope used to relay scientific data to the ground.

Among the duties of the high gain antenna is the relaying of photographic images to scientists.

The damage to the antenna threw the Hubble into a lower level "safe mode" that delayed the door opening until 8:46 a.m.

Then, when the door opened, it moved with more force than anticipated, jarring a pair of gyroscopes that keep the telescope stable.

The sensitive control mechanisms than alerted the computer. In response, the computer issued commands for "safe mode" and immobilized the observatory to keep it from looking into the sun.

At the time, the Discovery astronauts, who deployed the Hubble on Wednesday, were temporarily out of touch with mission control.

But when communications were regained, the shuttle fliers were quickly informed that the aperture door had opened.

"That's great news," said astronaut Steve Hawley. "There were handshakes and smiles all around up here. I bet it's that way down there, too.' Telescope engineers plan to carefully regain use of the ailing antenna by commanding it to move gradually until they know how far it can pivot without initiating safe mode commands.

They also are examining the possibility that the computer's safe mode software needs to be made less sensitive to the motions of the antenna and other moveable hardware, Harrington said.

Discovery commander Loren Shriver and his crew plan to end their five-day mission Sunday, landing at 8:48 a.m. at Edwards Air Force Base, Calif., if the weather cooperates.

NASA lead flight director Bill Reeves said forecasters are watching the movement of a cold front through the landing area that could prompt a one-day delay.