In this image provided by NASA, the space shuttle Endeavour is ferried by NASA's Shuttle Carrier Aircraft (SCA) over the Kennedy Space Center in the early morning hours of Sept. 19, 2012, as it departs for California.
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David J. Phillip/AP
Space shuttle Endeavour flies over Ellington Field in Houston atop the shuttle aircraft carrier Wednesday, Sept. 19, 2012. Endeavour is making a final trek across the country to the California Science Center in Los Angeles, where it will be permanently displayed.
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David J. Phillip/AP
Joey Morrison adjusts his space helmet after watching the shuttle aircraft carrier with space shuttle Endeavour atop, land Wednesday, Sept. 19, 2012, at Ellington Field in Houston.
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Space Shuttle Discovery lifts off from the Kennedy Space Center at Cape Canaveral, Fla., on April 5. Discovery's seven member crew is on a mission to deliver science racks, the last of the crew quarters and supplies to the International Space Station.
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Discovery's April 5 takeoff is one of the final four Shuttle missions, before NASA retires the craft.
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Space Shuttle Endeavour lifts off at the Kennedy Space Center in March 2008.
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Nigel Cook/Daytona Beach News-Journal/AP/FILE
Space Shuttle Discovery lights up the night sky as it streaks across past the 122-year-old Ponce de Leon Inlet Lighthouse in Ponce Inlet, Fla., in August 2009.
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Courtesy of Justin Dernier/EPA/AP/FILE
NASA's roll out of the Space Shuttle Discovery is slowed due to lightning in the area of Launch Pad 39A at Kennedy Space Center.
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The Space Shuttle Discovery performs the rendezvous pitch maneuver as it approaches the International Space Station for docking, with Earth in the background in August 2009.
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Courtesy of Scott Andrews and NASA
Space Shuttle Atlantis takes off from Cape Canaveral, Fla., in July 2009 on a mission to service NASA's Hubble Space Telescope. NOVA, on PBS, follows the journey of those involved in fixing the Hubble Telescope.
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Charles W. Luzier/Reuters/FILE
Space Shuttle Discovery is hoisted by a crane as it is separated from its external fuel tank inside the Vehicle Assembly Building at the Kennedy Space Center in Cape Canaveral, Fla., in June 2005.
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A low angle view of the nose and underside of Space Shuttle Endeavour is seen from the crew members on the International Space Station (ISS) in March 2008. Before docking with the station, Dominic Gorie, commander of the shuttle, flew the spacecraft through a roll pitch maneuver to allow the space station crew a good view of the shuttle's heat shield. ISS crewmembers took photos of the thermal protection system to send down for analysis by teams on Earth.
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The Space Shuttle Endeavour approaches the International Space Station as the two spacecraft prepare for docking in March 2008.
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David J. Phillip/AP/FILE
The first female Space Shuttle commander, Eileen Collins, poses next to a photograph of the Space Shuttle Columbia in July 1999 in Houston, Texas. Collins headed the crew during a five-day mission aboard Columbia.
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Spotters (l.) watch for clearance as the Space Shuttle Discovery is moved away from its original external fuel tank in the Vehicle Assembly Building at Kennedy Space Center in June 2005.
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Red Huber/Orlando Sentinel/AP
Space Shuttle Atlantis sits on the launch pad in Cape Canaveral, Fla., on Nov. 15.
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The moon is seen behind the Space Shuttle Endeavour at Kennedy Space Center in Cape Canveral, Fla., in November 2008.
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Space Shuttle Atlantis lands at California's Edwards Air Force Base in the Mojave Desert in February 2001, returning from a 13-day mission to the International Space Station.
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Space Shuttle Discovery makes its final approach to the launch pad in April 2005.
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Space Shuttle Discovery, atop a modified 747 aircraft, lifts off from Edwards Air Force Base in California in September 2009 en route to the Kennedy Space Center in Florida.