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Discoverer 4, also known as Corona 9001, was an American optical
reconnaissance satellite A reconnaissance satellite or intelligence satellite (commonly, although unofficially, referred to as a spy satellite) is an Earth observation satellite or communications satellite deployed for military or intelligence applications. The ...
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 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 Adva ...
of the
Department of Defense The United States Department of Defense (DoD, USDOD, or DOD) is an executive department of the U.S. federal government charged with coordinating and supervising the six U.S. armed services: the Army, Navy, Marines, Air Force, Space Force, ...
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 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) was an American Multinational corporation, multinational Conglomerate (company), conglomerate founded in 1892, incorporated in the New York (state), state of New York and headquartered in Boston. Over the year ...
. 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 Aircraft Company, Douglas-built Thor (rocket family), Thor first Multistage rocket, stage and the Lockheed Corporation, Lockheed-built RM-81 Agena, Agena ...
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, 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, 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