HOUSTON, Nov 5 (Reuters) Space shuttle Discovery undocked from the International Space Station today to end an eventful 11-day stay that included delivery of a new room for the space outpost and a risky repair to a power-producing solar panel.
Discovery, with pilot George Zamka at the helm, gently pulled away from the station 218 miles above the Pacific Ocean at the beginning of its two-day journey back to Earth.
''Shuttle departing,'' space station commander Peggy Whitson said as she rang a ship's bell in a naval salute that is tradition on the station.
''Thank you guys for the (Harmony) module and all your help,'' she radioed to Discovery, referring to an Italian-built module delivered by the shuttle.
Discovery was to fly around the station to take photographs for NASA engineers to study, then move about 40 miles away to perform a final inspection of the shuttle's heat shield.
The shuttle launched from Kennedy Space Center in Florida on October 23 and is scheduled to land there on Wednesday afternoon.
The seven shuttle astronauts bid a weepy farewell to the three space station crew members yesterday when they closed the hatch between the spacecraft in preparation for departure.
The shuttle crew includes returning space station flight engineer Clay Anderson, who was replaced by astronaut Dan Tani.
The 24-foot-long Harmony module delivered by Discovery was the first new room added to the outpost in six years. It adds 2,600 cubic feet of space to the 15,000 cubic feet the station had before its arrival.
Harmony also will be the berthing port for European and Japanese laboratories scheduled for delivery starting in December as NASA pushes to finish the outpost before the shuttle fleet is retired in 2010.
Station expansion plans may have been saved by a risky repair improvised by NASA after a solar power panel critical for the station's growing electricity needs ripped in two places while it was being unfurled on October 30.
Astronaut Scott Parazynski, on the fourth spacewalk of the mission, rode the station's robot arm, extended by a boom borrowed from the shuttle, out to the partially unfolded panel to thread it with hand-fashioned cables so it would not tear further.
With the cables, or ''cufflinks'' as NASA called them, in place, the panel was extended to its full 110-foot length, drawing cheers from Mission Control in Houston.
Had the repair failed, space station program manager Mike Suffredini said NASA might have had to jettison the panel, which would have caused not only a power shortage, but also stability problems for the station.
The panel was part of an 18-tonne truss the Discovery crew reinstalled from a temporary location as NASA prepares for station expansion.
Still to be repaired is a sluggish, 10-foot circular joint that rotates a separate set of solar arrays to keep them pointed at the sun for maximum electricity production.
A spacewalking Tani found metal shavings in the joint, which was installed on the station in June and had been acting up in recent weeks.
Suffredini said the station has sufficient power to support Europe's Columbus laboratory, planned for delivery on a December shuttle flight, five years behind schedule.
Until the rotary joint is repaired, it was uncertain if Japan's Kibo lab can be installed starting in February as planned, he said.
REUTERS PD HS1703