Extended Duration Orbiter

The Extended Duration Orbiter (EDO) program was a project by NASA to prepare for long-term (months) microgravity research aboard Space Station Freedom, which later evolved into the International Space Station. Scientists and NASA needed practical experience in managing progressively longer times for their experiments. The original Space Shuttle configuration usually provided a week to ten days of spaceflight. Several research projects and hardware components were part of the project, of which the EDO-pallet was one of the most visible, contracted by Rockwell International.^[1]

The first orbiter outfitted with the EDO hardware configuration was Endeavour, during its construction, and its last EDO flight was STS-67, in 1995.^[1][2] Endeavour's EDO modifications were removed in 1996 as part of routine maintenance, to reduce the orbiter's weight prior to STS-89.^[1] Columbia was outfitted for EDO flight during its maintenance period from August 10, 1991, through February 9, 1992, prior to STS-50, which was the first EDO flight.^[2][3] From 1992, through 1994, Atlantis went through a maintenance period, during which Atlantis was modified to have the provisions needed for EDO capability, but NASA chose not to proceed with the final modifications, and Atlantis never had EDO capability.^[1] The EDO-pallet used in these orbiter configurations was destroyed in the 2003 Columbia disaster.