Space station commander Peggy Whitson and flight engineer Dan Tani began repressurizing the Quest airlock module at 11:54 a.m. today, officially closing out a "hugely successful" seven-hour four-minute spacewalk to finish connecting the new Harmony module to the lab's power and cooling systems. The work clears the way for launch of the shuttle Atlantis on Dec. 6 to deliver the European Space Agency's Columbus research module to the outpost.

This was the third spacewalk in 15 days for the Expedition 16 crew, the 22nd EVA so far this year and the 99th devoted to station assembly and maintenance since construction began in 1998.

During today's spacewalk, Whitson and Tani connected a second set of ammonia coolant supply and return lines to the new Harmony module; finished reconnecting the station-to-shuttle power transfer system that lets docked shuttles tap into the lab's solar power grid; and carried out a second inspection of the station's contaminated right-side solar array rotary joint.

The astronauts also prepared the Harmony module's right side port for attachment of the Columbus research module next month while flight controllers at the Johnson Space Center in Houston worked through procedures to fully activate Harmony, checking out its electrical and cooling system connections. Activation had been planned for Sunday, but the work was moved up a day.

Space station flight director Derek Hassmann described today's excursion as a "hugely successful spacewalk."

"We were able to connect the node 2/Harmony module to the other string of the permanent ammonia cooling system," he said. "And because the crew got out the door early today as they always do, we were able to move early our node 2 final activations. Both node 2 thermal cooling systems are up and running inside the Harmony module, both MDMs, or computers, are powered up and both strings of power systems are up and running. That was an activity that wasn't scheduled until tomorrow. So once again, the crew has enabled us to get ahead."

Today's spacewalk capped one of the busiest three weeks in station assembly.

Harmony was launched to the station aboard the shuttle Discovery Oct. 23 and temporarily attached to the central Unity module's left-side port. After the shuttle departed, Whitson and flight engineer Yuri Malenchenko staged a spacewalk Nov. 9 to prepare the shuttle docking port on the front of the Destiny module for attachment to Harmony.

The docking port, known as pressurized mating adapter No. 2, was successfully moved to Harmony, using the station's robot arm, on Nov. 12. Two days later, the Harmony/PMA-2 "stack" was moved to the front of Destiny and robotically bolted in place. During a spacewalk Tuesday, Whitson and Tani connected one of two ammonia coolant loops and, running ahead of schedule, completed all required electrical connections. They also hooked up part of the station-to-shuttle power transfer system that lets docked shuttles tap into the lab's power grid.

During today's spacewalk, they finished the job and carried out the solar alpha rotary joint inspection to help engineers figure out what might be needed to fix it.

"When you think about it, with our three spacewalks, with our two significant robotics activities, what we've accomplished in the last 15 days is equivalent to a very ambitious shuttle assembly mission," Hassmann said. "What makes it special is we've accomplished everything I just described with just the three space station crew on board. ... So just an amazing accomplishment, it's a first for the international space station program."

As for the starboard solar alpha rotary joint, or SARJ, Hassmann said "what they discovered was race ring damage and particulate that was consistent with the damage Dan Tani observed (late last month)."

"What I gathered from today, and of course the engineers are going to go off and talk about this in great detail, but basically the damage is significant and is widespread," Hassmann said. "I'm not qualified or ready to draw conclusions here today, but we know that the damage is consistent around the race ring. The crew did report the gear teeth themselves looked clean and did not appear to be damaged or rubbed in any off-nominal way, which I took to be good news."

With Harmony now wired into the station's main power and cooling systems, NASA is clear to press ahead with launch of the shuttle Atlantis Dec. 6 on mission STS-122. Three spacewalks are planned for that mission, but it's not yet clear whether any additional SARJ work can be crammed into the already busy mission.

"What we've done is put the program in a better position on STS-122 to understand what they need to do in terms of either sARJ cleaning or SARJ repairs, etc.," Hassmann said. "So we've gathered additional data, verified the extent of the damage and now the folks have some work to do to quantify and plan exactly what they're going to do to address the SARJ issues on their mission."