Astronauts Successfully Complete Tricky Repair on Hubble
Saturday, May 16, 2009; 4:32 PM
The third and trickiest spacewalk of a challenging mission to repair and upgrade the Hubble Space Telescope appears to have been a wild success.
Astronauts John Grunsfeld and Andrew Feustel removed a refrigerator-sized, mirror-packed instrument called COSTAR. It was installed in 1993 to correct Hubble's blurry vision, but is no longer needed because new instruments have the same corrections built in. The astronauts replaced COSTAR with an instrument called the Cosmic Origins Spectrograph (COS), which is designed to probe the fundamental structure of the universe and search for filaments of dark matter that bind together the galaxies and all other visible matter.
Grunsfeld then undertook the most daunting task of the mission: With Feustel right behind him and handing him customized tools, he opened up the Advanced Camera for Surveys (ACS), which was never designed to be repaired ¿ not on Earth and certainly not in space.
The spacewalker extracted 32 screws to enable him to remove a panel covering the instrument's electronics. Grunsfeld's task was made all the more difficult by the awkward position of the instrument. He was unable to face the screws head on, only from a 45-degree angle. A strut partially blocked his vision.
Then he reached into the ACS with a tool that clamped each of the four electrical circuit cards. He was careful to keep his gloved hands away from any sharp edges that might pose a lethal hazard. Each card posed a serious hazard, with sharp edges that might nick a pressurized glove and expose Grunsfeld to the vacuum of space.
The white-knuckle moment went quickly and with only one brief hitch. For several minutes the fourth and last card became stuck, wedged against the strut. Grunsfeld, panting a bit at times but always calm, declared, "I think we'll get it." He retrieved a tool resembling needle-nosed pliers and, with much shaking and wiggling and prying, freed the card and delicately stowed it in a bag with the others.
The spacewalk, planned for six and a half hours, ran only six minutes over.
"Adrenaline is also a wonderful thing. And these guys are pumped. They are so eager to get out and do this job," said David Leckrone, the Hubble's senior scientist.
The mission has been a great success but has been a bumpy ride for the astronauts as the telescope reveals idiosyncrasies and even the simplest tasks prove unexpectedly daunting.
The first spacewalk, also conducted by Grunsfeld and Feustel, was stymied by a bolt that wouldn't budge and threatened to trap an old instrument in the telescope and ruin the hopes of scientists and engineers who had spent a decade building a replacement. The astronauts used three different tools with ever higher amounts of torque, to no avail. There were fears in space and on the ground that the bolt would shear. But Feustel, who fixes cars in his spare time, removed all limits on his socket wrench and, carefully applying ever more force, managed to loosen the bolt without shearing it.
Then on Friday, astronauts were unable to seat a new gyroscope. But they had brought along a spare, an old gyroscope that had been refurbished, and that popped into place without any problem.
Of the overall mission, Leckrone said, "I view it as 100 percent successful so far. It's just been tumultuous. The tasks we thought were simple have turned out to be painfully difficult."