"Discoverer" was the civilian designation and cover for the
Corona satellite photo-reconnaissance series of satellites managed by the
Advanced Research Projects Agency of the
Department of Defense and the
U.S. Air Force. The primary goal of the satellites was to replace the
U-2 spyplane in surveilling the Sino-Soviet Bloc, determining the disposition and speed of production of Soviet missiles and long-range bombers assets. The Corona program was also used to produce maps and charts for the Department of Defense and other US government mapping programs. The first series of Corona satellites were the Keyhole 1 (KH-1) satellites based on the
Agena-A upper stage, which not only offered housing but whose engine provided attitude control in orbit. The KH-1 payload included the C (for Corona) single, vertical-looking, panoramic camera that scanned back and forth, exposing its film at a right angle to the line of flight. The camera, built by
Fairchild Camera and Instrument with a f/5.0 aperture and focal length, had a ground resolution of . Film was returned from orbit by a single General Electric Satellite Return Vehicle (SRV) constructed by
General Electric. The SRV was equipped with an onboard small solid-fuel retro motor to deorbit at the end of the mission. Recovery of the capsule was done in mid-air by a specially equipped aircraft. The Discoverer program began with a series of three test flights whose satellites carried no cameras, all launched in the first half of 1959. There followed eight operational Discoverer satellites, all of them partial or complete failures, though Discoverer 11, launched 15 April 1960, carried a new vacuum-resistant film and was the first mission on which the onboard camera worked properly. Discoverer 11 failed on reentry, caused by the explosion of its spin motor. Though
Discoverer 12, a diagnostic flight to determine the causes of the various issues plaguing the program, was lost shortly after launch on 29 June 1960, the identical
Discoverer 13 functioned perfectly during its 10–11 August mission. With Discoverer 14, operational missions would resume. ==Spacecraft==