Hubble is redeployed into space after the servicing. Photo: NASA TV/Spaceflight Now

The Columbia astronauts are gearing up to release the rejuvenated Hubble Space Telescope back into open space early today, wrapping up a surprisingly successful five-spacewalk flight to upgrade the $2 billion observatory's electrical system and scientific instruments.

Astronaut Nancy Currie, operating the shuttle's 50-foot-long robot arm, plans to lock onto a grapple fixture on the side of the telescope around 1:52 a.m. EST. An electrical umbilical providing shuttle power will then be withdrawn an hour later. A few minutes after that, the 24,000-pound telescope will be hoisted above Columbia's cargo bay and oriented for redeployment.

At 3:52 a.m. EST, commands will be sent to power open Hubble's main aperture door, once again exposing its 94.5-inch primary mirror to starlight. Then, at 5:04 a.m. EST (1004 GMT), the space telescope will finally be released back into open space to resume its trail-blazing astronomical observations.

"One of the days that'll be the most exciting will be actually deploy day," said astronomer-astronaut John Grunsfeld, who has now carried out five Hubble servicing spacewalks in two mieeions. "That's because we've finished all the hard work, out doing the EVAs, and now we have the hard work of getting Hubble ready to go, making sure that the aperture door opens, that the high-gain antennas are deployed, the solar arrays are ready to go, and then finally opening up the (service platform) latches.

"Nancy will take the telescope up, put it over the payload bay and then very gently open up the arm snares and back away. At which point (commander) Scott Altman will fire the shuttle's jets to back out from under Hubble.

"The reason it's so interesting is that the particular approach ... takes the Hubble right over our heads," Grunsfeld said. "It goes right over those overhead windows. You know, they're big windows. And it's a 24,500-pound telescope. It's big."

During his previous Hubble visit in 1999, the view of Hubble slowly passing overhead just a few feet away was so startling that "even though we expected it, sort of instinctively everybody ducked as the telescope went over."

"Once it's gone, our job is basically done," Grunsfeld reflected. "We get to watch this great observatory that we've now made much better recede off into the distance. And I'm expecting I'll have some mixed feelings at that point as I did last time, you know, here's my friend the Hubble telescope and we're leaving it again. But it's just a beautiful sight to see the limb of planet Earth and this jewel in the sky going back out to do astronomy."

The astronauts will conduct their first round of media interviews since completing the Hubble overhaul starting at 7:57 a.m.