Discoverer 7

Discoverer 7, also known as Corona 9004, was an American optical reconnaissance satellite launched on 7 November 1959 at 20:28:41 GMT, the fourth of ten operational flights of the Corona KH-1 spy satellite series. Though the satellite was orbited successfully, its film capsule failed to separate from the main satellite.

Background


"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.

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 61 cm focal length, had a ground resolution of 12.9 m. 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.

Discoverer 7 was preceded by three operational missions and three test flights whose satellites carried no cameras, all launched in 1959.

Spacecraft
The battery-powered Discoverer 7 was a cylindrical satellite 1.5 m in diameter, 5.85 m long and had a mass after second stage separation, including propellants, of roughly 3850 kg. After orbital insertion, the satellite and SRV together massed 920 kg. The capsule section of the reentry vehicle was 84 cm in diameter and 69 cm long. 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.

Mission
Discoverer 7 was launched on 7 November 1959 at 20:28:41 GMT from Vandenberg LC 75-3-4 into a 159 km x 847 km polar orbit by a Thor-Agena A booster. 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. The satellite bus reentered on 26 November 1959.

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