By MIKE SCHNEIDER
Associated Press Writer
HOUSTON (AP) -- NASA managers have cleared space shuttle Endeavour to return to Earth on Sunday; now all they need is for the weather to cooperate.
Endeavour's seven astronauts hoped to end their space station delivery and repair mission at the Kennedy Space Center in Florida, where their families were waiting, but wind and storm clouds were strong possibilities at the landing strip. So NASA managers have activated the runway at Edwards Air Force Base in California as a backup site.
Although there are four landing opportunities -- two in Florida and two in California -- NASA managers only want to make three attempts Sunday afternoon before pushing the landing attempt back until Monday.
"We're going to be evaluating to make sure it's a good, safe place to land," said Bryan Lunney, entry flight director.
Endeavour's crew has enough supplies to last until Tuesday, but NASA officials want the crew on the ground no later than Monday.
NASA managers would prefer to land in Florida since that's where Endeavour is housed, and it would spare the space agency the $1.8 million price tag of flying the shuttle to Florida on the back of a 747 airliner.
The last time a shuttle landed at Edwards Air Force Base was in June 2007. The runway at Edwards is about 3,000 feet shorter than the 15,000-foot runway at Kennedy. But NASA officials said that shouldn't be a problem since Endeavour commander Christopher Ferguson and pilot Eric Boe have made extensive practice landings on the runway in training aircraft.
The weather at Edwards for both days looks favorable. The weather at Kennedy Space Center on Monday isn't forecast to be a whole lot better than it's expected to be on Sunday.
"It's borderline," Lunney said. "It's not an easy day."
After examining images from a late inspection of Endeavour's protective heat shield, NASA managers on Saturday cleared Endeavour for a return home. The managers wanted to make sure there were no gashes which could allow fiery gases to penetrate the shuttle, like what happened to the doomed Columbia space shuttle in 2003.
"Endeavour looks to me and to the experts to be as clean or cleaner than any vehicle that we've flown," said LeRoy Cain, chairman of the mission management team.
If it lands Sunday, Endeavour will end a 16-day mission during which the shuttle flew to the international space station delivering a new bathroom, kitchen, exercise machine, sleeping quarters and recycling system designed to convert urine and sweat into drinking water.
The new equipment will allow NASA to double the size of the space station crew to six by June.
The Endeavour crew also took four spacewalks to unjam a joint which rotates in the direction of the sun to generate power. The mission also rotated out a crew member at the outpost, orbiting 220 miles above Earth. U.S. astronaut Sandra Magnus replaced U.S. astronaut Greg Chamitoff, who was returning aboard Endeavour after living for six months at the station.
"I'm really looking forward to seeing my kids and my family," said Chamitoff, who has two children.
Up at the space station, meanwhile, a Russian supply ship arrived Sunday morning with Christmas presents, food, clothes and other items for the three residents. Cosmonaut Yuri Lonchakov had to use manual controls inside the station to guide the craft in for a docking because of a last-minute technical problem.
(Copyright 2008 by The Associated Press. All Rights Reserved.)