Today in Space: Hubble Telescope Surgery On Tap

No rest for the weary today on space shuttle Atlantis.

The third of five consecutive spacewalks to repair and upgrade the Hubble Space Telescope is widely anticipated to be the most difficult of all.

It includes surgery on a sensitive camera that wasn't designed to be repaired in space.

The Advanced Camera for Surveys, or ACS, was one of Hubble's most heavily used instruments until a power short in 2007 knocked out two of its three channels.

Mission specialists John Grunsfeld and Drew Feustel, who successfully completed the mission's first spacewalk on Thursday, will team up again.

They'll also install a high-powered new spectrograph, which will take the place of a box whose corrective optics famously fixed Hubble's blurry vision in 1993. It's no longer needed.

Click "Read more..." to take a look at the today's schedule.

5:31 a.m.: Crew wakes.
6:46 a.m.: Spacewalk preps begin.
9:16 a.m.: Spacewalk No. 3 begins.
9:46 a.m.: Corrective Optics Space Telescope Axial Replacement (COSTAR) removal / Cosmic Origins Spectrograph (COS) installation.
11:46 a.m.: COS "aliveness" test.
12:36 p.m.: Advanced Camera for Surveys (ACS) repair begins.
1:31 p.m.: ACS power down.
2:31 p.m.: ACS power up.
3:46 p.m.: Spacewalk No. 3 ends / COS functional test.
6:21 p.m.: Spacewalk No. 4 procedure review.
9:31 p.m.: Crew sleeps.

Note: these times reflect managers' decision to push back the crew wake-up time and the day's activities by one hour following Friday's marathon spacewalk by "Mike and Mike" - mission specialists Mike Massimino and Mike Good. We'll post NASA's officially revised schedule as soon as it's available.

At seven hours and 56 minutes, Friday's spacewalk was the eighth longest ever, knocking out of the top 10 another effort to replace gyroscopes on Hubble. It took almost as long for astronauts Jeff Hoffman and Story Musgrave to do the same job in 1993.

That was the first mission to service Hubble; Atlantis' is the last.

As always, you can watch all of today's action live here on The Flame Trench. Just click on the picture above to launch a NASA TV viewer.

And keep refreshing this page for updates throughout the day.