Atlantis crew replace gyroscopes in Hubble Space Telescope

Two NASA astronauts aboard space shuttle Atlantis took the second of their five space walks in their 11-day mission yesterday, to replace the 19-year old observatory's Hubble Space Telescope with six new gyroscopes in a 7-hour, 56-minute spacewalk.

Mission specialists Michael Good and Mike Massimino spun up the Hubble Space Telescope with six new gyroscopes and a new battery during a 7-hour, 56-minute spacewalk, which was the eighth longest spacewalk in history.

The second of the mission's five spacewalks team had accomplished all of the planned objectives. Those included replacement of all three rate sensing units (RSUs). Each rate sensing unit contains two gyroscopes, which help the telescope point itself. The spacewalkers could not get one of the three units into its slot, but they were able to install a spare that was carried on board because of the tight tolerances involved.

In 1999, when three of the six on-board gyroscopes had failed, NASA had installed a new set of gyros on Hubble and just prior to the current mission, another gyro had failed, which led to temporary disruptions in the Hubble's observation.

Good and Massimino removed one of the original battery modules from Bay 2 of the telescope and replaced it with a new unit. The module in Bay 3 is scheduled to be replaced by Mission Specialists John Grunsfeld and Andrew Feustel on Monday.

The batteries provide power to the telescope when it passes into the Earth's shadow and its solar arrays are not exposed to the sun.

Ground controllers at the Space Telescope Operations Control Center at Goddard Space Flight Center in Maryland confirmed that all six gyroscopes and the new battery passed preliminary tests.

Commander Scott Altman and Mission Specialist Megan McArthur completed a robotic arm inspection of 40 shuttle heat shield tiles that were not in full view during Tuesday's inspection. Based on imagery analysis, mission managers cleared all of Atlantis' thermal protection systems until a final pre-landing inspection on Tuesday.

Mike Massimino becomes the first to 'Tweet' From Space when he sent an email to Johnson Space Center, which then posted this message to his Twitter:

As astronaut Mike Massimino zoomed to rendezvous with the Hubble Space Telescope, he managed to reach out to thousands of people who are following his Twitter feed.

"From orbit, Launch was awesome!! I am feeling great, working hard and enjoying the magnificent views, the adventure of a lifetime has begun!" he said.

Massimino began 'tweeting' in early April about his training for the STS-125 shuttle mission to repair the Hubble Space Telescope. By Wednesday morning, more than 247,000 people were following his Twitter feed.

Aboard the shuttle, astronauts have one or two opportunities each day to send an email, but do not have access to the internet.