When space shuttle Atlantis rolls to a stop at the end of its current mission, the only remaining U.S. spacecraft capable of taking astronauts to orbit will be powered down for good. NASA's fleet of space shuttles, developed in the 1970s and first launched in 1981, have provided the nation with 30 years of almost uninterrupted access to space. But one by one, NASA has phased out its three remaining orbiters. The landing of Atlantis, set for 5:56 A.M. Eastern Daylight Time on July 21, will bring the end of the shuttle program.

The final mission, which began with a timely liftoff July 8, was a supply run to the International Space Station (ISS). Having made its deliveries, Atlantis undocked from the ISS on July 19 and began its journey back to Kennedy Space Center in Florida. The mission, officially designated STS-135, is the 33rd mission for the Atlantis orbiter and the 135th shuttle mission overall. The STS-135 crew are commander Christopher Ferguson, pilot Doug Hurley, and mission specialists Sandra Magnus and Rex Walheim.

If Atlantis is unable to make an approach to Kennedy due to weather in its first landing opportunity, it will have another chance at 7:32 A.M. Failing that, the orbiter will have landing slots available on July 22 at both Kennedy and the backup shuttle landing strip at Edwards Air Force Base in California.

Once the shuttle does return to Earth, the vehicle will be decommissioned and prepared for permanent display at Kennedy. NASA chose Atlantis, which has been in service since 1985, as the orbiter that will remain at Cape Canaveral; the other shuttles, Discovery and Endeavour, and a test vehicle, Enterprise, will head to museums in the Washington, D.C., Los Angeles and New York City areas, respectively.

Photo of Atlantis landing in 2010: NASA