NASA astronauts struggle with Hubble's new gyroscopes

Second spacewalk goes long as astronauts update gyroscopes, install batteries

Well into their second spacewalk, NASA's Atlantis shuttle astronauts have struggled today to install sensors that will keep the Hubble Space Telescope's view of the stars stable.

Astronauts Mike Massimino and Michael Good began today's spacewalk at 8:49 a.m. EDT. They have spent the majority of their time outside the space shuttle Atlantis wrestling with three rate sensor units. Each unit is part of a gyroscope that reports any movements to the telescope's computer, keeping the telescope, and the images it's taking, stable.

But things haven't gone well with the gyroscope assembly.

The astronauts were unable to set two of the units into place but worked around the problem by seating the third unit in the second slot and installing a spare unit in the third spot. Using the spare unit was a Plan B option, since NASA preferred to use the newly designed pieces. It's not clear yet why some of the units did not fit as designed.

As of 3 p.m., Massimino and Good, with the aid of fellow astronaut Megan McArthur, who was operating the shuttle's robotic arm, were working to replace one of the Hubble's battery sets. While Massimino was going to the space shuttle's storage area and unscrewing 12 bolts to retrieve the new battery set, Good was removing the old battery from Hubble by disconnecting six electrical connectors and unscrewing 14 bolts.

Midway through the afternoon, NASA estimated that the astronauts still had another two hours of work to do outside the space shuttle.

Today's work comes a day after two other astronauts -- mission specialists John Grunsfeld and Drew Feustel - installed a new backup computer system on the Hubble Space Telescope. During the spacewalk of seven hours and 20 minutes, the astronauts gave Hubble the new computer to replace the onboard system that had to be put into use after a technical failure last fall.

On Thursday, the astronauts also removed the telescope's Wide Field Planetary Camera 2 and replaced it with a new wide-field camera, which should enable Hubble to take large-scale, detailed photos.

The space shuttle Atlantis' 11-day mission is focused on repairing and upgrading the telescope, which has not been serviced since 2002. The repairs and additions should make Hubble far more powerful than it's ever been. And that will put Hubble in the position to make more, and more important, discoveries in the next five years than it has in the past two decades.

On Saturday, a team of spacewalkers is expected to repair Hubble's Advanced Camera for Surveys and install a new Cosmic Origins Spectrograph, which enables Hubble to observe faint ultraviolet targets. According to NASA, the spectrograph, one of the key pieces in Hubble's toolbox, will allow it to study the structure of the universe and how galaxies, stars and planets formed and evolved.

Copyright © 2009 IDG Communications, Inc.

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