Backdropped by a blanket of clouds, the space shuttle Atlantis is featured in this image photographed by an Expedition 23 crew member as the shuttle approaches the International Space Station during STS-132 rendezvous and docking operations on May 16, 2010.
This story was updated at 7:59 a.m. EDT.
CAPE CANAVERAL, Fla. - The space shuttle Atlantis has fired its engines to begin its approach for a Florida landing today to wrap up its final voyage into orbit as NASA's shuttle era draws one mission closer toward its end.
The shuttle fired its rocket engines to leave orbit at about 7:41 a.m. EDT (1141 GMT) to begin the long glide back to Earth. Landing for Atlantis is set for 8:48 a.m. EDT (1248 GMT) with commander Kenneth Ham at the controls.
"It's a great day in space and we're hoping it?s a great day in Florida," Ham radioed Mission Control early Wednesday. "Please keep the skies clear?because we look forward to coming home."
Atlantis will approach Florida from the southwest, flying over the Pacific Ocean, parts of Central America and the Caribbean before beginning its final approach to Runway 33 in Florida. The winged shuttle is effectively a 100-ton glider when it flies in Earth's atmosphere.
Aboard Atlantis with Ham are five astronauts ? pilot Dominic "Tony" Antonelli and mission specialists Garrett Reisman, Piers Sellers, Stephen Bowen and Michael Good.
The six astronauts are flying on what NASA expects to be Atlantis' final journey into space. The shuttle is due to retire this year, along with its sister shuttles Endeavour and Discovery.
Once Atlantis lands, only two more shuttle flights will remain before the fleet retires for good.
Atlantis actually had two chances to return to Earth today. If foul weather prevented the first attempt, the shuttle could have taken another trip around Earth and aim for a second opportunity at 10:22 a.m. EDT (1422 GMT).
NASA did not call up a backup landing site at Edwards Air Force Base for today's Earth return of Atlantis. The space agency prefers to land its shuttles at their home port in Florida because it saves on time and the cost of ferrying the orbiters home from across the country using a modified Boeing 747 jumbo jet.
Atlantis launched May 14 and is capping off a 12-day STS-132 mission to the International Space Station, where its crew installed the new Russian room Rassvet (which means "Dawn" in Russian) and a collection of spare hardware, including a new space-to-ground antenna and a six-pack of solar wing batteries.
"The mission is going really well," Reisman told reporters Tuesday. 'We've accomplished all of our primary objectives."
The six spaceflyers departed the orbiting laboratory on Sunday.
For Reisman, Good and Bowen ? the crew's three spacewalkers ? the highlight of the trip was the mission's three excursions outside of the station where they worked to install the new parts.
"The views were just amazing," Good said. "We're having a great time up here."
Though he predicted the highlight of the trip for at least one crewmember would come during landing.
"Maybe for the commander, his best moment is about to come ? or at least I hope it is ? when he puts this thing down on the ground and calls wheels stop," Good said.
Atlantis is flying its 32nd mission to space since it joined the shuttle fleet in October 1985. NASA's shuttles have been flying into space since 1981.
"The odometer currently reads about 120 million miles," Bowen said of the well-traveled orbiter.
While this is the last scheduled flight for Atlantis, there is a chance the shuttle could fly again. The orbiter is slated as the emergency rescue vehicle for the final planned shuttle flight, the STS-134 mission of Endeavour. If something goes awry during that trip, Atlantis could be launched to rescue the crew.
As soon as Atlantis is back on the ground, crews will get to work refurbishing the vehicle to ready it for that potential rescue launch.
NASA and some lawmakers have been lobbying to turn that rescue mission into a full-fledged extra shuttle flight, one which could deliver more spares and supplies to the space station in June 2011. But the White House has not yet approved adding the extra shuttle flight to NASA's current mission roster.
Atlantis' current mission, STS-132, is NASA's 132nd orbiter flight and the third of five shuttle missions planned for this year.
The shuttles Discovery and Endeavour are next in line to fly their final flights. Those missions are slated for September and late November.
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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 in Cape Canaveral, Fla., and Managing Editor Tariq Malik based in New York. Click here for shuttle mission updates and a link to NASA TV.