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Sunday, November 4, 2007

Space Station's Damaged Panel Is Fixed

Astronauts patched a damaged solar panel on the international space station yesterday during a tricky and dangerous seven-hour spacewalk.

Perched on the tip of an extension of the station's long robotic arm, astronaut Scott E. Parazynski snipped off tangles of broken and frayed wires that had ripped open two spots on the huge solar array, and installed five jury-rigged straps to reinforce the damaged area, allowing the panel to finally unfurl fully.

In this image provided by NASA television astronaut Scott Parazynski, top, gets into the foot restraints with the assistance of astronaut Douglas Wheelock at the end of the 90-foot robotic arm and boom extension, center, which will carry Parazynski for a 45-minute ride to the damage site at the start of the space walk to repair the damaged solar array Saturday Nov. 3, 2007.

"Excellent work, guys, excellent," space station commander Peggy A. Whitson said after the tense, painstaking job was finally done.

The spacewalk was considered particularly risky, with Parazynski venturing farther from the safety of the station than ever before. The repairs were unusually complicated because the astronauts were unable to fully assess the damage before getting close to the array and had to hope that their quickly improvised repair plans would work. Normally, such a repair mission would take weeks or even months of preparation and rehearsal.

But without the repairs, the damaged solar wing could have become structurally unstable, posing a hazard to the outpost and requiring that it be jettisoned.

Without the panel, the station would not have enough power to continue expanding. That could have forced a postponement of the installation of the next component, a European laboratory, next month. NASA is under pressure to complete the construction of the station before it retires the aging space shuttle fleet in 2010.

So, wearing protective spacesuits, Parazynski and astronaut Douglas H. Wheelock ventured out of the station, orbiting about 213 miles above the East Coast, just past 6 a.m. to begin the unprecedented job.

"Go out there and fix that thing for us," Whitson radioed just before the pair left the safety of the station's airlock.

With Wheelock positioned at the base of the solar array, Parazynski anchored his feet to the end of a 50-foot boom from the space shuttle; the boom was grasped in the middle by the station's 58-foot robotic arm. The arm carried him on a slow-motion, 45-minute trip half a football field away to just barely reach the damaged panel.

Dramatic live-television images showed Parazynski atop the extended arm with the bright orange solar array behind him and the brilliant blue and white Earth below.

Once there, Parazynski, an emergency-room physician, assessed the full extent of the damage for the first time, describing a daunting "hairball" of tangled wires in the area that was mangled when the solar panel was deployed Tuesday. The panel suffered two tears; the largest was about 2 1/2 feet long.

All the tools and all the metal parts of Parazynski's spacesuit were wrapped with insulating tape to minimize the risk of the astronaut getting shocked by the electric array, which is generating 160 volts. His bulky gloves were also covered with extra mittens for added protection.

Using an L-shaped device, dubbed a "hockey stick," to periodically and gently nudge the array away, as well as needle-nose pliers, vice-grips and clippers to cut away and secure loose wires, Parazynski methodically completed the repair, radioing his colleagues each step of the way.

Parazynski, one of the most experienced spacewalkers, installed five "cuff links," which the astronauts had pieced together from spare parts aboard the station. The three- to five-foot long pieces are insulated cables with aluminum plates at each end that Parazynski slipped into holes in the array like cuff links into a shirt sleeve. They are designed to support the damaged area and prevent further tearing.

Once all five were installed, Parazynski and Wheelock watched closely as ground controllers slowly unfurled the solar panel to its full 110-foot length. Parazynski then rode the robotic arm back to safety, returning inside the station with Wheelock at 1:22 p.m.

"It certainly was a really good day overall," said Dina Contella, lead spacewalk officer, during a briefing afterward.

The torn array, however, is just one of the problems facing the station. Metal shavings were discovered earlier in a joint on the station, jamming control of the solar arrays on that side. Space station managers are trying to determine how to fix that malfunction.

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