CAPE CANAVERAL, Fla. – Inside Orbiter Processing Facility-1 at NASA’s Kennedy Space Center in Florida, a long-angle view reveals the underside of space shuttle Discovery where the ferry flight doors are being installed. The work is part of the Space Shuttle Program’s transition and retirement processing of shuttle Discovery, which is being prepared for display at Smithsonian’s National Air and Space Museum, Steven F. Udvar-Hazy Center in Chantilly, Va. Discovery is scheduled to be transported atop a NASA Shuttle Carrier Aircraft modified 747 jet to Dulles International Airport in Virginia on April 17 and then moved to the Smithsonian for permanent public display on April 19. For more information, visit http://www.nasa.gov/shuttle. Photo credit: NASA/Jim Grossmann KSC-2012-1651

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.