This story was updated at 2:20 p.m. EDT.
The six astronauts flying aboard space shuttle Atlantis worked Tuesday to prepare their spacecraft for its final planned return to Earth.
STS-132 mission commander Ken Ham, pilot Dominic ?Tony? Antonelli and mission specialists Garrett Reisman, Piers Sellers, Stephen Bowen and Michael Good spent the day packing supplies, stowing equipment and testing Atlantis? flight control systems, all in an effort to bring the shuttle to a landing at NASA?s Kennedy Space Center (KSC) in Florida on Wednesday.
Their first opportunity to land, weather permitting, is targeted for 8:48 a.m. EDT (1248 GMT).
A chance of showers within about 30 miles of Atlantis' landing strip poses the only concern, entry flight director Tony Ceccacci said. NASA is still hopeful despite Florida's reputation for rainy summer weather, he added.
"It's a 50-50 chance no matter what the forecast says," Ceccacci said.
Today, mission managers also cleared Atlantis of any concerns related to its heat shield after reviewing data beamed to Mission Control from a Monday inspection to seek out signs of orbital debris damage. While engineers on Earth tackled that, the shuttle crew prepared Atlantis to once again fly in Earth's atmosphere.
?The crew will power up one of the auxiliary power units that provide its hydraulic power to the aerosurfaces on Atlantis and they will check those out along with some navigational aids that are used to find the landing site,? described lead shuttle flight director Mike Sarafin on Monday. ?Once those are complete, the crew will proceed into some cabin stow activities and Atlantis will be ready to come home.?
?The crew is doing exceedingly well and we all look forward if all goes well, to the return of Atlantis to the Kennedy Space Center,? Sarafin added.
Atlantis launched May 14 and has enough supplies to stay in orbit through Saturday. NASA has planned two landing attempts into KSC on Wednesday and two more on Thursday before calling up back-up sites at Edwards Air Force Base in California and in White Sands, New Mexico.
?We may get lucky and land on the first attempt and the weather may cooperate, or we may have to go around another day or two. We?ll just have to see how that plays out,? Sarafin said.
Other activities scheduled for today aboard Atlantis included the astronauts stowing the high bandwidth antenna through which they have been relaying live and recorded video, as well as exercise sessions to help prepare the crew for their return to gravity.
The shuttle astronauts also tool time to speak with reporters, including ABC News and trade jokes with Stephen Colbert, the comedian host of Comedy Central?s ?The Colbert Report."
NASA currently plans to retire Atlantis after this flight, but will ready the spacecraft to serve as a rescue ship as a safety precaution for the agency's final space shuttle mission slated to fly in late November. NASA and some lawmakers have been lobbying to take that rescue mission and turn it into a full-fledged extra shuttle flight for Atlantis, but the space agency has not yet received approval to add the mission to its schedule.
After Atlantis lands, only two more shuttle flights remain, on shuttles Discovery and Endeavour, before the orbiter fleet is retired. President Obama?s proposal for NASA?s future post-shuttle is for new technology development and launch vehicles aimed at sending astronauts to an asteroid or Mars.
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SPACE.com is providing complete coverage of Atlantis' STS-132 mission to the International Space Station with Senior Writer Clara Moskowitz and Managing Editor Tariq Malik based in New York. Click here for shuttle mission updates and a link to NASA TV.