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Discoverer 15
Mission type	Optical reconnaissance
Operator	US Air Force / NRO
Harvard designation	1960 MU
COSPAR ID	1960-012A
SATCAT no.	S00057
Mission duration	2 days
Spacecraft properties
Spacecraft type	CORONA KH-1
Bus	Agena-A
Manufacturer	Lockheed
Launch mass	810 kilograms (1,790 lb) after orbit insertion
Start of mission
Launch date	13 September 1960 22:13:39 GMT
Rocket	Thor DM-21 Agena-A; (Thor 246)
Launch site	Vandenberg LC 75-3-5
End of mission
Decay date	18 October 1960
Landing date	15 September 1960
Landing site	Pacific Ocean (SRV)
Orbital parameters
Reference system	Geocentric
Regime	Low Earth
Eccentricity	0.04094
Perigee altitude	199 kilometers (124 mi)
Apogee altitude	761 kilometers (473 mi)
Inclination	80.900°
Period	94.23 minutes
Epoch	13 September 1960 22:19:00
	Discoverer ← Discoverer 14 Discoverer 16 → Corona KH-1 ← Discoverer 14

Discoverer 15, also known as Corona 9010,^[1]^: 236 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. Launched on 13 September 1960, the satellite took reconnaissance photos of the Soviet Union. However, its recoverable film capsule was lost in the Pacific Ocean after reentry outside the recovery zone on 15 September.

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.^[4]

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.^[5]^: 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.^[6]

The Discoverer program began with a series of three test flights whose satellites carried no cameras, all launched in the first half of 1959. There followed eight operational Discoverer satellites, all of them partial or complete failures,^[1]^: 236 though Discoverer 11, launched 15 April 1960, carried a new vacuum-resistant film and was the first mission on which the onboard camera worked properly. Discoverer 11 failed on reentry, caused by the explosion of its spin motor. Though Discoverer 12, a diagnostic flight to determine the causes of the various issues plaguing the program, was lost shortly after launch on 29 June 1960, the identical Discoverer 13 functioned perfectly during its 10–11 August mission. Discoverer 14, launched 18 August, marked the first completely successful operational Discoverer mission.^[1]^: 59–61

Spacecraft

The battery-powered^[6] satellite was of similar configuration to prior Discoverers, being housed in an Agena-A stage and composed of a satellite bus and SRV equipped with camera. Discoverer 15 would be the last satellite to use the original C camera, Discoverer 16 and later flights being installed with the improved C' model. The satellite massed 810 kilograms (1,790 lb)^[1]^: 236

Mission

Launched into a polar orbit^[3] by a Thor-Agena A booster on 13 September 1960 at 22:13:39 GMT from Vandenberg LC 75-3-5 by a Thor DM-21 Agena-A rocket,^[7] Discover 15's camera functioned properly. However, the recovery vehicle re-entered at the wrong pitch attitude, and the capsule landed outside its recovery zone in the Pacific Ocean. This landing inaccuracy caused by the timing and angle of retrofire had been a perennial problem all of the prior (successfully deorbiting) Discoverers save for Discoverer 14. The Discoverer 15 capsule was located, but it sank before a recovery ship could reach it.^[5]^: 24

Discoverer 15's main body reentered Earth's atmosphere on 18 September 1960.^[2]

Results and legacy

The Corona program went on to comprise 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

References

^ ^a ^b ^c ^d ^e ^f ^g ^h Day, Dwayne A.; Logsdon, John M.; Latell, Brian (1998). Eye in the Sky: The Story of the Corona Spy Satellites. Washington and London: Smithsonian Institution Press. ISBN 1-56098-830-4. OCLC 36783934.
^ ^a ^b McDowell, Jonathan. "Satellite Catalog". Jonathon's Space Report. Retrieved 18 September 2021.
^ ^a ^b "Discoverer 15". NASA Space Science Data Coordinated Archive. Retrieved 18 September 2021.
^ "Discoverer 1". NASA Space Science Data Coordinated Archive. Retrieved 24 October 2020.
^ ^a ^b "Corona: America's First Satellite Program" (PDF). Central Intelligence Agency. 1995. Archived from the original (PDF) on June 12, 2007. Retrieved 25 January 2020.
^ ^a ^b Krebs, Gunter. "KH-1 Corona". Gunter's Space Page. Retrieved 7 November 2020.
^ McDowell, Jonathan. "Launch Log". Jonathon's Space Report. Retrieved 7 November 2020.