Discoverer 7

Thor Agena A with Discoverer 7, 7 November 1959

"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 assess. The Corona program was also used to produce maps and charts for the Department of Defense and other US government mapping programs.[2]

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.[3]^: 26 The camera, built by Fairchild Camera and Instrument with a f/5.0 aperture and 61 centimetres (24 in) focal length, had a ground resolution of 12.9 metres (42 ft). 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.[4]

Discoverer 7 was preceded by three operational missions and three test flights whose satellites carried no cameras, all launched in 1959.[1]^: 51–56

The battery-powered[4] Discoverer 7 was a cylindrical satellite 1.5 metres (4 ft 11 in) in diameter, 5.85 metres (19.2 ft) long and had a mass after second stage separation, including propellants, of roughly 3,850 kilograms (8,490 lb).[5] After orbital insertion, the satellite and SRV together massed 920 kilograms (2,030 lb).[1]^: 236 The capsule section of the reentry vehicle was 84 centimetres (33 in) in diameter and 69 centimetres (27 in) long.[5] Like its operational predecessors, Discoverers 4–6, Discoverer 7 carried the C camera for its photosurveillance mission.

The capsule was designed to be recovered by a specially equipped aircraft during parachute descent, but was also designed to float to permit recovery from the ocean. The main spacecraft contained a telemetry transmitter and a tracking beacon.[5]

Discoverer 7 was launched on 7 November 1959 at 20:28:41 GMT from Vandenberg LC 75-3-4[6] into a 159 kilometres (99 mi) x 847 kilometres (526 mi) polar orbit by a Thor-Agena A booster.[5] One day after launch, a command was sent to initiate SRV separation for deorbiting and recovery. However, the capsule failed to separate from its satellite bus.[1]^: 236 The satellite bus reentered on 26 November 1959.[7]

CORONA achieved its first fully successful flight with the mission of Discoverer 14, launched on August 18, 1960.[1]^: 59 The program ultimately comprised 145 flights in eight satellite series, the last mission launching on 25 May 1972.[1]^: 245 CORONA was declassified in 1995,[1]^: 14 and a formal acknowledgement of the existence of US reconnaissance programs, past and present, was issued in September 1996.[1]^: 4