Sunday, November 4, 2007

Space station repairs end in success

A physician astronaut successfully stitched a torn solar panel Saturday, in a risky and unprecedented space walk to ensure an adequate power supply at the International Space Station, NASA said.

Astronaut Scott Parazynsky, a medical doctor by profession, spent more than four hours attached to the end of a robotic boom knitting together the damaged panels with makeshift wire "cufflinks" to fix the problems caused by a snagged wire when the panels unfurled.

"It appears you have some kind of surgery to do Dr. Parazinsky," shuttle commander Pamela Melroy told the experienced spacewalker as she watched his every move through binoculars from inside the Discovery probe, currently docked at the station (ISS).

The mission carried significant danger as touching the panels risked a shock from the 300-volt current they carried.

"Beautiful," Parazynsky said as he wrapped up the in-space fix-it job.

"Outstanding work," said Peggy Whitson, one of the controllers at Houston, Texas Mission Control.

The US National Aeronautics and Space Administration had made fixing the solar arrays the top priority for the Discovery shuttle mission because without it there was a risk the tear could spread and render the power-generating wing useless.

The mission unfolded live on television screens, with cameras and microphones aboard the international Space Station and on the astronaut's helmet catching all of the discussion and directions.

Parazynsky, 46, had to first cut the guy-wire that caused the problem; it quickly recoiled into a reel at the base of the wing.

To avoid the electric shock risk, Parazynsky had to work with a makeshift "hockey stick," an L-shaped tool wrapped in tape to prod the panels and help stitch through holes in the solar panels the five cufflink-like wire tabs fashioned by the astronauts aboard the ISS.

Ahead of the operation David Wolf, head of spacewalk training at NASA's center in Houston, said electrocution was "conceivable but extremely unlikely," adding that in such a case the astronaut would not be burned but could receive a "mild shock."

While he received coaching from both the ISS and the NASA Mission Control base at Houston, Texas, cameras showed Parazynsky twisting and bending the cufflinks to jam them through the holes to secure the panels.

Parazynski was attached by his feet to a 15-meter (49-foot) extension boom joined to the space station's 18-meter (59-foot) robotic arm, while Doug Wheelock stayed close watching the progress and giving directions to Stephanie Wilson and Dan Tani, who were maneuvering the robotic arm from inside the ISS.

After the stitching operation, NASA engineers using controls remotely in Houston slowly unfurled the solar pannel to its full extention of 76 meters (250 feet) -- when it snagged it was at 80 percent of its full length.

Wheelock and Parazynski, who closely watched the unfurling operation to spot any trouble, spent seven hours and 19 minutes in open space before completing the repair and returning to the ISS' decompression chamber at 1722 GMT.

The solar array, one of three on the space station, is critical to providing extra electricity for planned European and Japanese science labs.

The European Columbus laboratory is due to be delivered to the ISS in December and the Japanese Kibo lab in April 2008.

Working with the stiff spacesuit gloves made the job all the more difficult for Parazynski, who nevertheless deftly threaded the cufflinks into the holes.

Wolf earlier characterized the work as "like sewing with mittens on."

Parazynski was also farther out from the shuttle than on previous spacewalks -- an entire hour from safety instead of the customary 30 minutes if he needed to end the walk in an emergency.

If there are no more problems, Discovery is scheduled to undock from the space station on Monday and return to Earth on Wednesday. It blasted off on the mission on October 23.