Dr. Scott E. Parazynski, riding on an extension of the station's robotic arm, said that his close-up view of the repair site revealed a "hairball" of wire with guide wire for the array caught up in the wire running through the connecting the panels.
Mission managers knew that wires had become snagged and had torn the array in its deployment, but did not know the nature of the snag and had hoped that it would be as simple as moving a wire off of a hinge. The description by Dr. Parazynski, an astronaut who has been an emergency room physician, confirmed a description from Pamela A. Melroy, the commander of the mission, who was watching from inside the station with binoculars at the beginning of the spacewalk. "It doesn't look like an easy, just rattle-it-and-shake-loose-the-grommet kind of situation," she said.
With the close-up view now available, she said, "Sounds like you have some surgery to do, Dr. Parazynski."
He replied, "I think so."
The spacewalk calls for clearing the snag and using five straps with ends like cufflinks to bind the damaged panels. Dr. Parazynski, a veteran spacewalker on his fifth NASA mission, is working to restore the structural integrity of the 110-foot-long solar "wing" so that it can continue to provide power to the orbital outpost. The first cufflink slid easily into place along the array shortly before 9 a.m.
"That was a beautiful thing to see that cufflink go through the hole," Ms. Melroy said.
"Yes, it was," Dr. Parazynski replied. That strap, 66 inches long, was intended to stabilize the array so that Dr. Parazynski could get down to the work of clearing up the problem with the wires.
With the sun at his back and his shadow stark against the brilliantly lit golden array, Dr. Parazynski began cutting wires after 9:50, cautiously planning each snip in consultation with Ms. Melroy and mission controllers on the ground and keeping clear of the swaying array.
By shortly after 10 a.m., Dr. Parazynski had cut the offending wires and moved on to attaching the remaining four cufflinks.
Mission managers said that while the set-up for the spacewalk was arduous, and involved higher risk and less planning and practice than normally go into such activities, the tasks themselves might be accomplished relatively simply.
"It's a snag clear; it's not rocket science," Dina Contella, the lead spacewalk officer for the mission, said in a briefing on Friday with reporters.
And though concern outside of NASA had run high over the possibility that Dr. Parazynski might suffer electric shocks, perhaps even a fatal one, from the solar array, the mission managers stressed at the Friday news conference that such an event was highly unlikely. Derek Hassmann, the lead flight director for the station, said that an astronaut would have to be touching the array with a metal part of his suit at a point in which the array's insulation had come off, and have another part of the suit touch a different part of the array "in order to complete the circuit," he said.
Still, the list of warnings read to Dr. Parazynski by Paolo Nespoli, who was choreographing the spacewalk from the station, was extensive, and included warnings about touching sharp edges from bolts, solar cells, hinges and other areas of the array. "I'm not sure there's much less to touch," Dr. Parazynski said.
"We're not even halfway through the warnings," Mr. Nespoli said, and went on to warn against touching areas with "pinch points" and high electrical current, which carry a risk of shock and "molten metal."
Col. Douglas H. Wheelock is also taking part in the spacewalk, positioned at the base of the array to provide visual cues to Dr. Parazynski.
If the procedure does not work, the array might have to be jettisoned, and future construction on the station might be constrained by its reduced ability to produce power, especially since the solar arrays on the right-hand side of the station are currently parked because of mechanical problems with the rotary joint that helps point them toward the sun.
Derek Hassmann, the lead flight director for the station, said, "We need to address one of these two problems before we proceed" with further construction missions.
The job puts Dr. Parazynski farther from the safety of the airlock than any astronaut has gone in the history of the space station program. If there are problems - for example, glove damage or a failure of the suit's oxygen supply - returning to safety could take somewhat longer than the 30 minutes that his backup oxygen supply would cover.
Mission managers say they are confident that despite the additional risk, Dr. Parazynski will be safe. Astronauts have covered exposed metal on his suit and tools with insulating tape to prevent arcing. Mr. Hassmann said that the likelihood of risk from shock was extremely small.
"We don't expect there to be any issue," he said.