Final Spacewalk for Hubble Repairs

18 May 2009

U.S. astronauts are undertaking their fifth and final spacewalk Monday to repair the Hubble Space Telescope.

NASA TV image of astronaut John Grunsfeld putting on foot restraints to upgrade the Hubble telescope, 18 May 2009

Spacewalkers John Grunsfeld and Andrew Feustel left the Atlantis space shuttle at 1220 UTC (8:20 am EST) to begin the nearly six hour operation.

So far, the two have successfully installed a fresh set of three - 57 kilogram batteries, leaving plenty of time to replace the telescope's sensor and insulation.

The insulation was to have been replaced Sunday. However, the astronauts experienced technical difficulties and were unable to complete the installation. Mission planners decided to add the task to Monday's list of things to do.

NASA is hoping the repairs will extend the life of the telescope by at least another five years. The Hubble is expected to be released on Tuesday.

On Sunday, astronauts Mike Good and Mike Massimino replaced the power supply unit for the Space Telescope Imaging Spectrograph, a powerful instrument that allows NASA to identify black holes and to monitor galaxies.

The two spacewalkers on Sunday had trouble unbolting a handrail that had to be removed in order to start their repairs. While they were not able to loosen one of the handrail's bolts, they were able to bend it out of the way and proceed with their work.

Their spacewalk lasted more than eight hours. It was the sixth-longest spacewalk in the history of the U.S. space program.

The mission to Hubble is more dangerous than other missions because the telescope is sharing an orbit with debris left behind by satellite collisions and rocket launches.

The astronauts are further challenged because they can only work with the supplies they are able to carry with them on the shuttle. In missions to the International Space Station, astronauts have enough supplies on the station to last up to three months.