Crew members and NASA scientists say they are "pumped up" for a mission next month that will take the shuttle Endeavour to the limits of its fuel supply and challenge four spacewalkers to complete the longest and most complex chores ever attempted in orbit.
Seven astronauts will blast off Dec. 1 on an 11-day mission to correct a mirror flaw in the Hubble Space Telescope and install equipment to ensure its survival into the next century.
The work will require 30 hours of spacewalks by four astronauts who have spent more than 400 hours rehearsing the mission in water tanks. Even so, they all expect problems they haven't anticipated.
"Space is the frontier," said program manager Ken Ledbetter. "And when you're pushing the edge of the frontier, you sometimes run into the unexpected. We think we are prepared as much as we can be for that."
Their success is critical not just to the long-term survival of the $1.5 billion telescope but also to NASA's credibility with the public and Congress. The future of other big projects, such as NASA's planned space station, may be threatened if the Hubble repair mission fails.
The $251 million service call is scheduled for liftoff before dawn Dec. 1, with a return to the Kennedy Space Center in Florida before dawn on Dec. 12. It calls for at least five, and possibly as many as eight, spacewalks.
In addition to installing a new camera and new optics to correct a flaw in Hubble's primary mirror, astronauts hope to replace the satellite's faulty solar panels, failed gyroscopes and other gear to keep alive Hubble's search for black holes, planets circling other suns, and mysteries in the farthest reaches of the universe.
At the Goddard Space Flight Center in Greenbelt yesterday, officials acknowledged the repair mission's importance to NASA. But they said they are too busy making it work to worry about implications of failure.
"It is important because it demonstrates NASA's capability to do on-orbit servicing of Hubble itself," said mission director Randy Brinkley. "That in itself is enough to worry about."
The veteran crew includes Commander Richard Covey, 47; pilot Kenneth Bowersox, 37; payload commander Story Musgrave, 58; and mission specialists Tom Akers, 42, Jeffrey Hoffman, 49; Claude Nicollier, 49; and Kathryn Thornton, 41.
Once launched, the shuttle begins a race to catch up with Hubble in orbit 355 miles above the Earth. It is the shuttle's highest rendezvous ever, leaving little fuel for maneuvering in orbit and a return to Earth.
"We're going with tanks full, but we don't have a lot of tolerance for a missed mission," said Mr. Covey. "We definitely need to be successful on the first attempt."
For their work to be regarded as successful, the astronauts will have to accomplish at least two things:
* Correction of the telescope's mirror flaw for at least some astronomers, by either replacing the Wide Field/Planetary Camera or installing COSTAR, a package of mirrors that corrects the optics for three other instruments.
* Installation of at least three improved gyroscopes. Hubble needs three working gyroscopes to point to and track stars. It has six on board, but three have failed and a fourth is acting up.