Discoverer 6

Image:Thor agena a discoverer 6.jpg

"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.{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1959-002A|title=Discoverer 1|publisher=NASA Space Science Data Coordinated Archive|access-date=24 October 2020}}

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.{{cite web |title=Corona: America's First Satellite Program |url=https://www.cia.gov/library/center-for-the-study-of-intelligence/csi-publications/books-and-monographs/corona.pdf |archive-url=https://web.archive.org/web/20070612220818/https://www.cia.gov/library/center-for-the-study-of-intelligence/csi-publications/books-and-monographs/corona.pdf |url-status=dead |archive-date=June 12, 2007 |publisher=Central Intelligence Agency |access-date=25 January 2020 |date=1995}}{{rp|26}} The camera, built by Fairchild Camera and Instrument with a f/5.0 aperture and {{convert|61|cm}} focal length, had a ground resolution of {{convert|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.{{cite web|url=https://space.skyrocket.de/doc_sdat/kh-1.htm|title=KH-1 Corona|first=Gunter|last=Krebs|publisher=Gunter's Space Page|accessdate=7 November 2020}}

Discoverer 6 was preceded by Discoverer 5, launched 13 August 1959, Discoverer 4, launched 25 June 1959, and three Discoverer test flights whose satellites carried no cameras, launched in the first half of 1959.{{rp|51–56}}

The battery-powered Discoverer 6 was a cylindrical satellite {{convert|1.5|m}} in diameter, {{convert|5.85|m}} long and had a mass after second stage separation, including propellants, of roughly {{convert|3850|kg}}.{{cite web|url=https://nssdc.gsfc.nasa.gov/nmc/spacecraft/display.action?id=1959-006A|title=Discoverer 6|publisher=NASA Space Science Data Coordinated Archive|access-date=30 October 2020}} After orbital insertion, the satellite and SRV together massed {{convert|864|kg}}.{{cite book|last1=Day|first1=Dwayne A.|last2=Logsdon|first2=John M.|last3=Latell|first3=Brian|title=Eye in the Sky: The Story of the Corona Spy Satellites|publisher=Smithsonian Institution Press|location=Washington and London|date=1998|isbn=1-56098-830-4|oclc=36783934|page=236}} The capsule section of the reentry vehicle was {{convert|84|cm}} in diameter and {{convert|69|cm}} long. Like Discoverers 4 and 5, Discoverer 6 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.

Discoverer 6 was launched on 19 August 1959 at 19:24:44 GMT from Vandenberg LC 75-3-4{{Cite web|url=http://planet4589.org/space/log/launchlog.txt|title=Launch Log|last=McDowell|first=Jonathan|publisher=Jonathon's Space Report|access-date=24 October 2020}} into a {{convert|212|km}} x {{convert|848|km}} polar orbit by a Thor-Agena A booster. As with Discoverer 5, the onboard camera failed, this time in the satellite's second orbit rather than the first. It is likely that it had broken on its way out of the supply container, which had also occurred on the prior flight.{{rp|56}} The SRV separated from its satellite bus the day after launch and deorbited for recovery over the Pacific but was not recovered. The satellite bus reentered on 20 October 1959.{{Cite web|url=https://www.planet4589.org/space/log/satcat.txt|title=Satellite Catalog|last=McDowell|first=Jonathan|publisher=Jonathon's Space Report|access-date=9 April 2020}}

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

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