Corona (satellite)
The Corona program was a series of American strategic reconnaissance satellites produced and operated by the Central Intelligence Agency Directorate of Science & Technology with substantial assistance from the U.S. Air Force. The Corona satellites were used for photographic surveillance of the Soviet Union (USSR), the People's Republic of China, and other areas beginning in June 1959 and ending in May 1972. The name of this program is sometimes seen as "CORONA", but its actual name "Corona" was a codeword, not an acronym for anything.
The Corona satellites were designated KH-1, KH-2, KH-3, KH-4, KH-4A and KH-4B. KH stood for "Key Hole" or "Keyhole" (Code number 1010), and the incrementing number indicated changes in the surveillance instrumentation, such as the change from single-panoramic to double-panoramic cameras. The "KH" naming system was first used in 1962 with KH-4 and the earlier numbers were retroactively applied. There were 144 Corona satellites launched, of which 102 returned usable photographs.
Read more about Corona (satellite): History and Costs, Technology, Discoverer, ELINT Subsatellites, Declassification, Launches, Photo Gallery