May 15, 2009

Second Spacewalk of Hubble Mission Completed

Space shuttle Atlantis crew members Michael Massimino and Michael Good ventured out for the mission's second of five spacewalks on Friday to continue making upgrades to the Hubble Telescope as the shuttle made its 60th orbit of the mission.

"It is a beautiful day outside," Massimino said as they began the six-hour spacewalk. "Anybody home?"

Good and Massimo began the second spacewalk of the STS-125 mission at 8:49 a.m. EDT. Their tasks for the day include replacing the orbiting observatory's gyroscopes, which help direct the telescopes vision.

"Those gyros are absolutely critical," said Hubble project manager Preston Burch.

They are currently working to remove the old rate sensor units. Massimino is disconnecting two electrical connectors while Good removes three bolts. Once they are disconnected, they will install the new units by connecting the electronics and tightening the bolts.

The two space walkers will repeat this process two more times as they replace the remaining two units, according to NASA.

NASA has previously replaced Hubble's gyroscopes during a 1999 mission after four of its six gyroscopes had failed. The observatory is designed to operate with three gyros although it can survive with two, or even one.

Following the new rate sensor installation, the pair will begin the first half of the mission's battery replacement procedure. Working from Hubble's Bay 2, Good and Massimo will replace the first of two battery modules. Each module weighs 460 pounds and contains three batteries that power the telescope during the night.

The second battery module is scheduled to be installed during the fifth and final spacewalk, said NASA.

Massimino, who also worked on upgrade installations to Hubble in 2002, became the first astronaut to send a tweet from space.

"From orbit: Launch was awesome!!" Massimo said in his first tweet. "I am feeling great, working hard, & enjoying the magnificent views, the adventure of a lifetime has begun!"

Today's spacewalk was Good's first.

"Welcome to the wonderful world of working in a vacuum," Massimino told Good as they ventured outside the cabin.

On Thursday, Atlantis astronauts John Grunsfeld and Andrew Feustel successfully installed the new Wide Field Camera 3 to the telescope during the mission's first spacewalk. They also swapped out the Science Instrument Command and Data Handling Unit, installed a soft capture mechanism, lubricated three of the shroud doors, and one of the three latch-over center kits.

The mission will include other upgrades such as the installation of the so-called Cosmic Origins Spectrograph, which will observe the light put out by extremely faint, far-away quasars and see how that light changes as it passes through the intervening gas between distant galaxies.

Hubble has received four upgrades since it was launched by shuttle Discovery in 1990, where it was put into an orbit of 304 nautical miles above the Earth.

NASA believes the current upgrades will allow Hubble to continue operations for at least five years. Meanwhile, its successor, the James Webb Space Telescope is under development.

Atlantis is expected to return to Earth on Friday of next week.


Image Credit: NASA


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