As the crew of Atlantis awaited the results of a final heat shield inspection the space shuttle headed to Earth.
A camera attached to the shuttle's robotic arm surveyed the wings and nose cap after Atlantis undocked from the international space station Tuesday.
NASA engineers study those images to make sure the shuttle can withstand the intense heat of re-entering Earth's atmosphere before they give final approval for a Thursday landing at Cape Canaveral, Florida. The inspections became routine after shuttle Columbia broke apart on re-entry in 2003, killing seven astronauts.
Flight director Cathy Koerner said Wednesday she did not anticipate any problems.
During their nearly 10 days at the space station, Atlantis' astronauts installed a new truss segment on the orbiting outpost, unfurled a new pair of power-generating solar arrays, and activated a rotating joint that allows the new solar arrays to track the sun.
Their 11-day mission was extended to 13 days to also give them time to repair a thermal blanket on the shuttle that partially peeled back during lift off.
On Wednesday, Atlantis' astronauts were scheduled to check the shuttle's engine and thermal control systems.
Even if the shuttle's heat shield is cleared for landing, the weather might not cooperate.
A front in the Florida panhandle was expected to send showers to the Kennedy Space Center on Thursday and Friday.
"Get us some good weather for Thursday if you can. It doesn't have to be good. It just has to be good enough," shuttle commander Rick Sturckow told Mission Control.
Atlantis has enough fuel to orbit until Sunday, but managers want the shuttle to land by Saturday. The flight would only be extended to Sunday if there were technical problems that needed to be fixed.
In a daily report sent up to the astronauts Wednesday morning, Mission Control said landing opportunities at Kennedy, the primary landing site, look slightly better on Friday and Saturday. A backup landing site in California might be considered on Friday. That backup site plus another in New Mexico would be activated Saturday if necessary.
Atlantis was only cleared to leave the space station after Russian computers there passed a test Monday to take control of the station's thrusters. The computers had crashed last week but were revived over the weekend. On Atlantis, the astronauts had turned off equipment to conserve fuel in case the shuttle needed to stay longer.
More than an hour after the shuttle undocked Tuesday, a piece of debris that looked like a blanket and at least five tiny flashing particles floated past the space station. Engineers were still reviewing video and photographs to identify the debris.
"It's not a big concern," said Mike Suffredini, NASA's space station program manager.
The shuttle is bringing back astronaut and former space station resident Sunita Williams, whose more than six months in space set a record for the longest spaceflight by a woman. Astronaut Clay Anderson, her replacement, was taken to the station aboard Atlantis.
"I just can't wait to be home," Williams said Wednesday.
NASA said the space station and the space shuttle would be visible Wednesday night from the United States. Cities with the best chances of getting a view were Denver, Detroit, San Francisco and Washington, said NASA spokeswoman Kylie Clem.
Russian officials have repeatedly declared that Israeli aviation poses a threat to the Russian military in Syria.