Discoverer 4, also known as Corona 9001, was an American optical reconnaissance satellite launched on 25 Jun 1959 at 22:47:45 GMT, the first of ten operational flights of the Corona KH-1 spy satellite series, and the first satellite to be equipped for photo surveillance. The satellite was not successfully orbited. Its loss spurred improvements of its rocket booster to ensure the success of subsequent missions.

Background

"Discoverer" was the civilian designation and cover for the

Corona Corona (from the Latin for 'crown') most commonly refers to: * Stellar corona, the outer atmosphere of the Sun or another star * Corona (beer), a Mexican beer * Corona, informal term for the coronavirus SARS-CoV-2, which causes the COVID-19 di ...

satellite photo-reconnaissance series of satellites managed by the

Advanced Research Projects Agency The Defense Advanced Research Projects Agency (DARPA) is a research and development agency of the United States Department of Defense responsible for the development of emerging technologies for use by the military. Originally known as the Adv ...

of the

Department of Defense Department of Defence or Department of Defense may refer to: Current departments of defence * Department of Defence (Australia) * Department of National Defence (Canada) * Department of Defence (Ireland) * Department of National Defense (Philipp ...

and the

U.S. Air Force The United States Air Force (USAF) is the air service branch of the United States Armed Forces, and is one of the eight uniformed services of the United States. Originally created on 1 August 1907, as a part of the United States Army Sign ...

. 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 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 General Electric Company (GE) is an American multinational conglomerate founded in 1892, and incorporated in New York state and headquartered in Boston. The company operated in sectors including healthcare, aviation, power, renewable en ...

. 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 4 was preceded by three Discoverer test flights whose satellites carried no cameras.

Spacecraft

The battery-powered Discoverer 4 was composed of two sections: the satellite proper and the SRV. Together, they massed () after orbit insertion. It was the first Discoverer equipped with the C camera and the first satellite built for photo surveillance.

Mission

Launched 25 Jun 1959 22:47:45 GMT from Vandenberg LC 75-3-5 by a

Thor-Agena Thor-Agena was a series of orbital launch vehicles. The launch vehicles used the Douglas-built Thor first stage and the Lockheed-built Agena second stages. They are thus cousins of the more-famous Thor-Deltas, which founded the Delta rocke ...

rocket, the satellite was lost when its carrying Agena failed to reach orbit.

Legacy

As a result of the loss of Discoverers 3 and 4 during launch, the Air Force Ballistic Missile Division (BMD) halted flights until the Agena failures could be evaluated. In consultation with

Space Technology Laboratories TRW Inc., was an American corporation involved in a variety of businesses, mainly aerospace, electronics, automotive, and credit reporting.http://www.fundinguniverse.com/company-histories/TRW-Inc-Company-History.html TRW Inc. It was a pionee ...

, BMD slightly altered the Agena's propulsion, control, and computer systems. The fuel system of the Thor first stage was also altered. These changes ensured the successful launch of Discoverer 5 in August 1959. CORONA achieved its first fully successful operational flight with the mission of

Discoverer 14 Discoverer 14, also known as Corona 9009, was a spy satellite used in the Corona program managed by Advanced Research Projects Agency (ARPA) of the Department of Defense and the United States Air Force. On 19 August 1960, usable photographic film ...

, 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.

References

{{Orbital launches in 1959 Spacecraft launched in 1959 Spacecraft which reentered in 1959