Astronauts Wind Up Hubble House Call : NASA: Crew struggles to finish repairs before releasing laboratory tonight. Final work involves parts not designed to be serviced in space.

HOUSTON —  In the last of five dramatic spacewalks this week, astronauts Wednesday night struggled with stubborn plugs and computer glitches as they finished up repairs of the Hubble space telescope before releasing the rejuvenated observatory back into orbit tonight. NASA hopes to pay it another house call before the end of the century.

The crew’s last housekeeping repairs Wednesday night were more mundane than the modifications to the Hubble’s flawed optics performed earlier in the week. But they turned out to be more exasperating because, unlike many other systems in the space telescope, they involved parts that were not designed to be serviced in space.

“It is a little less user-friendly and a little more involved,” said Hubble program manager Ken Ledbetter.

With surprising aplomb, space-suited astronauts floating amid the stark gold-and-white payload bay of the space shuttle Endeavour have corrected the Hubble’s notorious blurred vision, installed a new camera system, restored its broken solar power panels and then performed electronic brain surgery on its computer.

The new optical devices they installed promise to give astronomers full use of the $1.5-billion telescope for the first time.

“We’ve got basically a new telescope up there,” said mission specialist Jeffrey A. Hoffman, who was scheduled to conduct the final spacewalk with mission specialist F. Story Musgrave. “It’s going to be real exciting for the astronomical community and for the whole world to see what Hubble really can do with a good set of eyeballs.”

NASA scientists were pleased with the mission’s apparent success but anxious for the telescope’s first crisply focused views of distant quasars and nebulae, which won’t come for more than six weeks.

“It is extremely difficult to keep from becoming excited right now, but I’ve got to try,” said David Leckrone, Hubble project senior scientist. “We have just completed eye surgery on the Hubble space telescope. We won’t know if it is successful until we take the bandages off weeks from now.”

Preliminary tests by engineers at NASA’s Goddard Space Flight Center show that the new equipment is working mechanically. If the new optics can be properly aligned and calibrated in the coming weeks, he said, “We will have a complete and capable observatory with all the tools astronomers need to ply their trade and go after the big questions.”

Early today, NASA engineers expected to unfurl the Hubble’s new, more efficient solar power panels, which will supply the telescope with electricity. The astronauts have been able to concentrate most of their attention on fixing the Hubble this week because the space shuttle Endeavour, NASA’s newest orbiter, has been trouble-free, agency officials said.

“Endeavour continues to show its worth as a facility for construction and servicing,” Milt Heflin, lead flight director for the Hubble mission at the Johnson Space Center, said Wednesday.

BACKGROUND

The Hubble space telescope, authorized by Congress in 1977, is named for American astronomer Edwin P. Hubble, whose observations in the 1920s from Mt. Wilson Observatory overlooking Pasadena established the existence of galaxies besides our own. His research also led him to conclude that the universe is expanding.