Time Will Tell If Hubble Fix Worked
In the fifth and final spacewalk of their mission, shuttle Columbia astronauts went back out Friday and did their best to revive a disabled infrared camera on the Hubble Space Telescope.
John Grunsfeld and Richard Linnehan connected a prototype refrigeration system to the camera, which hasn't worked for three of its five years.
It was a last-ditch attempt by NASA to open the camera's infrared eyes so they can peer once again into the dark, dusty regions of the universe. Officials consider the cooling system experimental and won't know for at least a month whether it can do the job.
Grunsfeld and Linnehan opened the door to the telescope bay containing the infrared camera and mounted the new cooler on the floor near the instrument. "It's nice to see an old friend," said Grunsfeld, who was on the last servicing mission in 1999.
The spacewalkers hung a 13-foot-long radiator on the outside of the telescope, then began the cumbersome work of routing and connecting all the electrical cables and plumbing.
Mission Control started the spacewalk late to give Columbia's crew time to recover from Thursday's excursion. Friday's spacewalk, at more than seven hours, lasted almost as long.
Before going back inside Columbia, Grunsfeld and Linnehan thanked all the teams that helped make the mission a success and said astronomers everywhere will enjoy the beauty and inspiration of the pictures that will be coming from Hubble.
"HST is definitely an icon of science, but also the peaceful use of space," Grunsfeld said. "And so all the people above us on Planet Earth: May there be peace on Earth."
The comatose camera — the Near Infrared Camera and Multi-Object Spectrometer, or Nicmos for short — was launched to Hubble in 1997. But it stopped working in 1999 when a small heat leak caused its supply of nitrogen ice to run out early. The ice was needed to keep the infrared detectors at their operating temperature of minus 350 degrees.
To fix the problem, NASA devised a $21 million system that uses nonexpendable neon gas as the coolant and a refrigeratorlike compressor.
The compressor has three tiny turbines that spin at 400,000 revolutions per minute, roughly 50 to 100 times the operating speed of a typical car engine. The beauty of this system is that it's virtually vibration-free — crucial for Hubble's precise picture-taking.
"It's very much pioneering-type technology," said Hubble program manager Preston Burch.
This new cooling system accompanied John Glenn to orbit aboard space shuttle Discovery in 1998, in a flight test. Burch said it worked well, but had to be retooled to reduce the risk of contamination and power demands.
It will take at least two weeks to chill the camera's infrared detectors and another three weeks to know whether the new cooling system was able to resuscitate the instrument. If restored, the camera could resume its study of young star clusters, exploding stars and planetary atmospheres.
With their 11-day flight winding down, Columbia's astronauts will release the rejuvenated Hubble Telescope on Saturday. They will return to Earth on Tuesday, bringing back the solar wings, power controller, obsolete camera and other old telescope equipment that was removed to make room for the new.
By Marcia Dunn