Their work in orbit accomplished, space shuttle Endeavour's astronauts got the green light Saturday to return to Earth, but were warned "pretty iffy" weather at the main landing site could send them across the country or keep them up an extra day.

On Saturday afternoon — 24 hours before the planned landing — Mission Control informed the seven astronauts that Endeavour had been cleared for re-entry following analysis of data beamed down from a final thermal survey of their ship. The space shuttle was found to be free of any serious defects caused by space junk that could jeopardize the descent.

The astronauts noticed a small strip of material floating away as they checked out their flight systems, but Mission Control told them not to worry. It was merely a 3-inch label.

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Astronaut Gregory Chamitoff was especially eager to come back: He's been off the planet, away from his wife and 3-year-old twins, since the end of May.

"My watch is telling me that it will be 182 days for me today away from home," Chamitoff said Saturday. "A lot of people have to spend time away from home, but I've been lucky to have a really spectacular place to live for the last half year.

"I'm very proud that all of us here are leaving the space station a better, more spectacular place than it was when we arrived."

Endeavour and its crew left the international space station on Friday, ending a nearly two-week visit that set the stage for population growth next year. The astronauts furnished the orbiting outpost with a new bathroom, kitchen, exercise machine, sleeping quarters and recycling system designed to convert urine and sweat into drinking water.

NASA's goal is to double the size of the space station crew, to six, by June.

Endeavour originally was supposed to land Saturday, but mission managers kept the astronauts at the space station an extra day to help with the balky urine processor. The weather was beautiful Saturday at Kennedy Space Center, but a cold front was expected to bring stiff wind and possibly thunderstorms on Sunday and even worse conditions on Monday.

NASA called up its backup landing site in California, Edwards Air Force Base, just in case.

Endeavour has enough supplies to stay up until Tuesday.

One final task remained late Saturday afternoon: the ejection of a miniature research satellite from Endeavour's payload bay. The satellite — dubbed Picosat and measuring 10 inches long and 5 inches high and wide — is meant to test new solar cell technology for the Defense Department.

Commander Christopher Ferguson said he was "extremely satisfied" with how the 16-day mission had gone. He and his crew were bringing back about 7 liters of recycled urine and condensation from the space station's new system for testing — "yesterday's coffee" as the astronauts like to call it.

"We came up here with a very long list of objectives, and although we encountered a glitch or two along the way, we've managed to achieve them all," Ferguson said in a series of TV interviews.

The astronauts had to spend extra time on the urine processor getting it to work. And one of the spacewalkers — Heidemarie Stefanyshyn-Piper — lost a $100,000 tool kit. The bag full of grease guns and other tools was expected to keep circling Earth until spring.

Asked by an interviewer if NASA would take the $100,000 out of her paycheck, she replied: "Well, if they do, I guess I'll be working for NASA for a long, long, long time."

Perhaps the most interesting observation about the space station came from Stephen Bowen, a former Navy submarine officer making his first shuttle flight.

"As soon as I got on the space station, I noticed the distinct pseudo-submarine odor, not quite as intense," Bowen said with a chuckle. "But it was very familiar, and those that know it will remember it well."