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.

Corona started under the name "Discoverer" as part of the WS-117L satellite reconnaissance and protection program of the US Air Force in 1956. The WS-117L was based on recommendations and designs from the RAND Corporation. The United States Air Force credits the Onizuka Air Force Station as being the "birthplace of the Corona program." In May 1958, the Department of Defense directed the transfer of the WS-117L program to Advanced Research Projects Agency. In FY1958, WS-117L was funded by the AF at a level of US$108.2 million (inflation adjusted US$0.90 billion in 2017). For Discoverer, the Air Force and ARPA spent a combined sum of US$132.3 million in FY1959 (inflation adjusted US$1.09 billion in 2017) and US$101.2 million in FY1960 (inflation adjusted US$0.82 billion in 2017). According to John N. McMahon, the total cost of the CORONA program amounted to $US 850 million.

The Corona project was pushed forward rapidly following the shooting down of a U-2 spy plane over the Soviet Union in May 1960.

The Corona satellites used special 70 millimeter film with a 24-inch (610 mm) focal length camera. Manufactured by Eastman Kodak, the film was initially 0.0003 inches (7.6 µm) thick, with a resolution of 170 lines per 0.04 inches (1.0 mm) of film. The contrast was 2-to-1. (By comparison, the best aerial photography film produced in World War II could produce just 50 lines per mm (1250 per inch) of film.) The acetate-based film was later replaced with a polyester-based film stock that was more durable in earth orbit. The amount of film carried by the satellites varied over time. Initially, each satellite carried 8,000 feet (2,400 m) of film for each camera, for a total of 16,000 feet (4,900 m) of film. But a reduction in the thickness of the film stock allowed more film to be carried. In the fifth generation, the amount of film carried was doubled to 16,000 feet (4,900 m) of film for each camera for a total of 32,000 feet (9,800 m) of film. This was accomplished by a reduction in film thickness and with additional film capsules. Most of the film shot was black and white. Infrared film was used on mission 1104, and color film on missions 1105 and 1008. Color film proved to have lower resolution, however, and was never used again.

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