Astronauts wrap up 4th spacewalk to repair Hubble

Monday, May 18, 2009 at 2:16 AM Posted by Beijing News


Two spacewalking astronauts overcame a stuck bolt, a fickle power tool and other aggravations Sunday to revive a long-inactive science instrument inside the Hubble Space Telescope.

The outing from space shuttle Atlantis by astronauts Mike Massimino and Mike Good to surgically repair a spectrograph that identifies super massive black holes was considered by NASA to be the most intricate spacewalk of the mission.

It turned equally frustrating for the two men as they were forced to contend with obstacles that required extra doses of ingenuity, patience and elbow grease and stretched their activities to just over eight hours.

"Oh, for Pete's sake," Massimino complained when the battery-operated ratchet he was using lost power. Later, the veteran astronaut cursed as he wrestled to discard the cover plate he'd pulled from the Space Telescope Imaging Spectrograph STIS into a storage bag.

Massimino and Good focused all of their efforts on the STIS, which was installed in the telescope by shuttle astronauts in 1997. The spectrograph, which astronomers use to gather information about the chemical composition, temperature, pressure and velocities of celestial targets, was sidelined by a power failure in 2004.

In order to replace a failed power converter, Massimino and Good had to replace an internal circuit card. The extraction required Massimino to remove a protective cover secured by 111 small screws using an arsenal of custom made hand tools.

But access to the cover and the many tiny fasteners was obstructed by a hand rail that had to be removed first. The rail was secured by four bolts, one of them badly stripped.

After several failed attempts to turn the bolt with wrenches, Massimino offered to snap the hand rail off using some old-fashioned muscle.

"Okay, here we go," said Massimino as he broke away the fixture.

"Awesome," responded Mission Control.

The two men then made quick work of removing a protective cover, replacing the bad circuit card and installing a new cover held down by a pair of latches rather than screws.

The spectrograph quickly passed an electrical test, but Hubble engineers planned to spend Sunday night conducting a more exhaustive test of the instrument.

Mission Control postponed plans to patch a damaged region of the telescope's exterior until Monday, when astronauts embark on the last of five gruelling spacewalks that form the cornerstone of an ambitious strategy to extend mind-boggling space observations with 19-year-old Hubble by at least another five years.

On Saturday, spacewalkers John Grunsfeld and Drew Feustel breezed through a similar but less demanding repair of Hubble's Advanced Camera for Surveys, a heavily used seven-year-old instrument that encountered a disabling electrical short in early 2007.

The short sapped three internal imagers, though experts were able to recover one of them within a month of the power disruption.

When an overnight testing session ended on Sunday, US space agency NASA announced that Grunsfeld and Feustel had recovered one of the two long-disabled internal imagers.

The revived Wide Field channel accounts for about 90 percent of the survey camera's observations, many of them focused on studies of galaxies and distant star systems used to calculate how rapidly the universe is expanding.

Hubble is a cooperative project between NASA and the European Space Agency.



A participant attends the 17th Life Ball in Vienna. AFP/Joe Klamar

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