The Hubble Space Telescope was set free to explore the heavens Wednesday.
The deployment was the climax of a tension-filled day during which it looked as though two astronauts aboard Discovery would have to venture outside and free a balky piece of equipment, the solar array.The 40-foot-long solar array refused to unfurl, and round controllers at the Goddard Space Flight Center here solved the problem instead when they ordered the telescope to ignore a sensor that had automatically stopped the array from unfurling.
Thus, at 3:38 p.m. EDT, as the Discovery sped over the Pacific Ocean and neared the West Coast, astronomer Steven Hawley gently released the $1.5 billion instrument from the shuttle's robotic arm.
The sensor indicated the fragile array was under such tension that it threatened to tear itself apart, but ground controllers determined that the sensor was faulty and overrode the automatic shutoff.
Moments later, the gold array stretched out like a wing shimmering in the brilliant sunlight.
No sight could have been finer to the dozens of scientists who have worked for years on the space telescope project. The two solar arrays provide the energy to keep the telescope's batteries charged.
Even the telescope itself would have been at risk if it had been impossible to deploy both solar arrays.
``She's finally on orbit,' Richard Truly, chief of the National Aeronautics and Space Administration, said a few minutes later. ``The first of NASA's Great Observatories is now on station.'
The Hubble will be followed by three other space telescopes - one later this year and two others by the end of the decade - each designed to study the universe at different wavelengths of light.
Partly because of the immense importance of the telescope, coupled with a number of minor problems that plagued ground controllers throughout the deployment, it all added up to a ``really stressful' day, said a normally subdued Mike Herrington, director of orbital verification.
But the troubles with the solar array were about the only serious problems that the astronauts faced Wednesday.
However, even with the telescope floating freely around the Earth, Discovery's crew was not quite ready to give up its stewardship over the Hubble. The shuttle will remain within about 40 miles of the telescope until sometime Friday so that it can zip back up if anything goes wrong.
Ground controllers will try out the telescope's sophisticated maneuvering system Thursday.
If they are satisfied that they have absolute control over the vehicle they will pass another milestone sometime Friday - they will order the telescope to remove its lens cap.
The cap is designed to protect the telescope if it should accidentally point toward the sun, which would burn out some of the instruments, so controllers want to be sure the scope will respond to every command before removing the cap.
That should be a very routine maneuver, but if for any reason the lens cap fails to respond to the command, the Discovery will rendezvous with the telescope and McCandless and Sullivan will finally get their space walk.
If all goes well, the shuttle will be freed from its responsibilities in time for its scheduled landing Sunday morning at Edwards Air Force Base in California.
In a few days, possibly as early as Tuesday, astronomers hope to capture their first image with the telescope, although it would be an engineering maneuver and the photo may be fuzzy. It will be several months before all the bugs are out, all the instruments have been calibrated, and the Hubble assumes its place in history.