Spacewalking astronauts installed the last set of solar wings at the international space station Thursday, accomplishing the top job of shuttle Discovery's mission.
Steven Swanson and Richard Arnold II struggled with some cable connections, but managed to hook everything up.
"It wasn't quite as smooth as we had hoped, but those guys did a great job," astronaut Joseph Acaba told Mission Control.
Mission Control radioed its praise: "We're delighted to accept delivery and installation."
The next milestone will be Friday, when the folded-up solar wings are unfurled.
Manpower was needed inside and out to attach the $300 million segment to the space station. Swanson and Arnold helped their colleagues inside the shuttle-space station complex cautiously move the 31,000-pound, 45-foot-long girder into position with a robotic arm.
"Keep coming," one of the spacewalkers said. "It really looks good to me."
The actual attachment occurred an hour into the spacewalk, and the hookups were completed two hours later.
Discovery delivered the new wings earlier this week. It's the final set of solar wings to be installed at the 10-year-old space station and will bring it to full power. It's also the last major American-made piece of the space station.
Before winding up their six-hour spacewalk, Swanson and Arnold released and removed the locks and cinches holding down the wings. That will allow the 115-foot wings to be extended on Friday, an even more nerve-racking procedure than the one Thursday. The last time astronauts tried to unfurl a solar wing in 2007, it snagged on a guide wire and ripped. Emergency repairs were required.
Six solar wings already are in place. The new ones will bring the number to eight, with four on each side.
The space station "is almost symmetric, looking forward to that becoming permanent today," Mission Control said in a wake-up message to the astronauts.
NASA needs the extra electrical power that the new wings will provide to boost the amount of research being done at the space station. The pace of science work will pick up once the number of station crew members doubles to six; that's supposed to happen in two more months.
"Give us some more power," the space station's skipper, Mike Fincke, told the spacewalkers as they floated out early in the afternoon.
By evening, the spacewalkers wrapped up their work. They hurled four thermal covers from the new framework out into space, away from the station, then watched from a safe distance as the accordion-style radiator on the segment unfolded.
"Welcome back aboard the space station," Fincke told them. "It's a lot bigger than when you left it."
It was the third spacewalk of Swanson's career and the first for Arnold, a former schoolteacher.
The spacewalk 220 miles up was the first of three planned for Discovery'svisit. There should have been four, but delays in launching the shuttle cut the mission short.
Discovery needs to leave the space station Wednesday so that a Russian spacecraft can bring up a fresh crew.