Space Shuttle Columbia (OV-102) was a Space Shuttle orbiter manufactured by Rockwell International and operated by NASA. Named after the first American ship to circumnavigate the upper North American Pacific coast and the female personification of the United States, Columbia was the first of five Space Shuttle orbiters to fly in space, debuting the Space Shuttle launch vehicle on its maiden flight in April 1981. As only the second full-scale orbiter to be manufactured after the Approach and Landing Test vehicle Enterprise, Columbia retained unique features indicative of its experimental design compared to later orbiters, such as test instrumentation and distinctive black chines. In addition to a heavier fuselage and the retention of an internal airlock throughout its lifetime, these made Columbia the heaviest of the five spacefaring orbiters; around heavier than Challenger and heavier than Endeavour. Columbia also carried ejection seats based on those from the SR-71 during its first six flights until 1983, and from 1986 onwards carried an imaging pod on its vertical stabilizer. During its 22 years of operation, Columbia was flown on 28 missions in the Space Shuttle program, spending over 300 days in space and completing over 4,000 orbits around Earth. While it was seldom used after completing its objective of testing the Space Shuttle system, and its heavier mass and internal airlock made it less than ideal for planned Shuttle-Centaur launches and dockings with space stations, it nonetheless proved useful as a workhorse for scientific research in orbit following the loss of Challenger in 1986. Columbia was used for eleven of the fifteen flights of Spacelab laboratories, all four United States Microgravity Payload missions, and the only flight of Spacehab's Research Double Module. The Extended Duration Orbiter pallet was used by the orbiter in thirteen of the pallet's fourteen flights, which aided lengthy stays in orbit for scientific and technological research missions. Columbia was also used to retrieve the Long Duration Exposure Facility and deploy the Chandra observatory, and also carried into space the first female commander of an American spaceflight mission, the first ESA astronaut, the first female astronaut of Indian origin, and the first Israeli astronaut. At the end of its final flight in February 2003, Columbia disintegrated upon reentry, killing the seven-member crew of STS-107 and destroying most of the scientific payloads aboard. The Columbia Accident Investigation Board convened shortly afterwards concluded that damage sustained to the orbiter's left wing