The seven Atlantis astronauts had been due to return to Earth Thursday, but thunderstorms scuttled attempts to land at the Kennedy Space Center in Cape Canaveral, Florida and instead the shuttle was directed to the California base.

NASA is sensitive about landing the shuttle in bad weather as clouds below 2,400 meters (7,800 feet) block the pilot's vision as the ship hurtles down to the landing strip.

Friday's landing at 15:49 pm (1949 GMT) came as the clock was ticking, with the shuttle's hydrogen batteries, which provide its electric power, only having one more day of life left.

The US space agency would have preferred to land the shuttle in Florida as it costs nearly two million dollars to return it from California piggy-backed atop a Boeing 747 and this could affect the schedule of future missions.

More than an hour after landing, the crew were still on board powering down the computers and checking all systems, although they had been allowed to remove their orange flight-and-entry suits.

Earlier shuttle commander Rick Sturckow and pilot Lee Archambault had fired up the thrusters after being given the green light to leave orbit and come plummeting toward the Edwards Air Force Base in California.

The thrusters are used to slow down the orbiter, which reaches speeds of more than 26,000 kilometers (16,000 miles) per hour on the way toward Earth.

After breaking out of orbit with a blast known as a "deorbit burn," the shuttle plummets earthward 20 times faster than a commercial airliner. But unlike a jet, the pilot gets only one try, due to lack of power.

"We are stopped," Sturckow said as the Shuttle drew gracefully to a halt, a red parachute billowing out behind it to slow its speed, and ending a mission that lasted 13 days, 20 hours, 12 minutes and 44 seconds.

Houston praised the crew for "a good job ... continuing to expand the space station and adding the modules from our international partners and stepping stones for the rest of the NASA exploration plan."

While docked at the International Space Station, the astronauts successfully installed a new truss segment, expanding the station's laboratory with a new set of power-generating solar arrays.

The astronauts ventured out on four spacewalks to set up the truss and fix a thermal blanket which was damaged when the shuttle shot into orbit.

The small hole in the heat shield had prompted concerns for the craft's safety on re-entry, but NASA declared it fit to return after the repairs.

Engineers stressed it posed no threat to the crew, unlike the broken tile that caused shuttle Columbia to break up on re-entry in February 2003, killing all seven astronauts on board.

Atlantis brought back with it Indian American astronaut Sunita Williams, who had been on the ISS since December. She set a new record for the longest uninterrupted space flight by a woman, breaking the mark set by Shannon Lucid in 1996 of 188 days, and four hours.

The entire crew was meanwhile to undergo medical checks once they leave the shuttle.

Atlantis left behind one crew member, Clayton Anderson, who is to stay on the orbiting research lab for four months alongside two Russian cosmonauts.

NASA plans at least 12 more shuttle missions, with Atlantis next set to head to the ISS in about six months time.

Three more shuttle missions are planned this year, as the US space agency races to finish building the 100-billion-dollar ISS by 2010, when the space agency retires its three remaining orbiters.

It considers the station a vital part of US ambitions to send a manned mission to Mars.

Related Links
File image of a space shuttle landing at Edwards AFB. Shuttle at NASA
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Space Shuttle News at Space-Travel.Com

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