Atlantis' astronauts gave the ship's wings and nose one last inspection Monday with a remotely operated TV camera and laser, and NASA said there appeared to be no damage that would prevent the shuttle from coming home.
Atlantis and its six crew members are set to touch down early Wednesday at the Kennedy Space Center after spending 11 days in space to deliver a major addition to the international space station and conducT three spacewalks to install it.
The astronauts attached a 50-foot (15-meter) boom to the shuttle's robotic arm to inspect for any damage. The boom has a TV camera and a laser imagery system attached to its end. An identical survey was conducted on Day 2 of the mission.
Monday's inspection was conducted while the shuttle was about 50 miles (80 kilometers) from the space station.
If the astronauts had found the type of damage that could cause a deadly accident, the shuttle would have been able to return to the station. However, the space station had its own problems Monday.
Space station crew members pulled an alarm and donned protective gear after smelling a foul odor that turned out to be a burning rubber and a harmful chemical leaking from an oxygen system. NASA said the leak was not life-threatening, and the crew cleaned up the spill.
The inspection of the shuttle two days before landing was one of several safety procedures instituted after the Columbia disaster in 2003. Foam that fell off the big external fuel tank during liftoff gashed Columbia's wing and caused the shuttle to disintegrate during re-entry into Earth's atmosphere. All seven astronauts were killed.
NASA flight director Paul Dye said an initial look at the inspection footage from Atlantis showed no areas of concern with the ship's thermal protective skin.
"We didn't see anything to the naked eye ... that would bother us," Dye said. "The only thing obvious was that everything looked very, very good."
Even though Atlantis looked to be in good health, NASA probably won't give final approval to land the shuttle until Tuesday.
The weather forecast for landing Wednesday in Florida wasn't promising but was expected to improve on Thursday and Friday. Atlantis has enough supplies to stay in space two extra days and could also land at Edwards Air Force Base in California.