Colloquially known as Big Bird, the KH-9 Hexagon was the largest, and the last, of the US film-return recon satellites. Weighing in at 25,000lbs for the basic vehicle and more than fifty feet in length, Hexagon replaced the earlier Corona satellites. The Lockheed Missiles and Space Company built the bus, while Perkin Elmer constructed the primary sensor and McDonnell the reentry vehicles.
The two main cameras, of folding path configuration, could operate in unison to yield stereoscopic photos. Film was then taken up and moved to one of the four reentry vehicles, which were snagged over the Pacific by JC-130s. Some KH-9 missions incorporated a mapping camera, and these had a fifth RV.
The first KH-9 was launched atop a Titan IIID in June 1971, and the last launch attempt (the only failure in the program) took place in April 1986. The last three launches used Titan 34Ds.
Tiangong 1 and X-37B sighting photos
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