CAPE CANAVERAL, Fla. -- Space shuttle Endeavour glistens in the sun on Launch Pad 39A at NASA's Kennedy Space Center in Florida. The rotating service structure (RSS) that protects the shuttle from the elements and provides access to its components is open to allow crews to move the primary payload for Endeavour's STS-134 mission into the pad's structure before installing it into the spacecraft's cargo bay. Endeavour and its six-member STS-134 crew are targeted to lift off April 19 at 7:48 p.m. EDT to deliver the Alpha Magnetic Spectrometer-2 (AMS) and Express Logistics Carrier-3 to the International Space Station. This is Endeavour's final scheduled mission. For more information visit, www.nasa.gov/mission_pages/shuttle/shuttlemissions/sts134/index.html. Photo credit: NASA/Frank Michaux KSC-2011-2402

The Space Shuttle program was the United States government's manned launch vehicle program from 1981 to 2011, administered by NASA and officially beginning in 1972. The Space Shuttle system—composed of an orbiter launched with two reusable solid rocket boosters and a disposable external fuel tank— carried up to eight astronauts and up to 50,000 lb (23,000 kg) of payload into low Earth orbit (LEO). When its mission was complete, the orbiter would re-enter the Earth's atmosphere and lands as a glider. Although the concept had been explored since the late 1960s, the program formally commenced in 1972 and was the focus of NASA's manned operations after the final Apollo and Skylab flights in the mid-1970s. It started with the launch of the first shuttle Columbia on April 12, 1981, on STS-1. and finished with its last mission, STS-135 flown by Atlantis, in July 2011.