Spy satellite

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KH-4B Corona satellite

Lacrosse radar spy satellite under construction

A spy satellite (officially referred to as a reconnaissance satellite) is an Earth observation satellite or communications satellite deployed for military or intelligence applications. The first generation type (i.e. Corona ^[1] ^[2] and Zenit) took photographs then ejected canisters of photographic film, which would descend to earth. Corona capsules were retrieved in mid-air as they floated down on parachutes. Later spacecraft had digital imaging systems and downloaded the images via radio links.

In the United States, the most information is available on programs that existed up to 1972. Some information about programs prior to that time is still classified, and a small trickle of information is available on subsequent missions. A few up-to-date reconnaissance satellite images have been declassified on occasion, or leaked, as in the case of KH-11 photographs which were sent to Jane's Defence Weekly in 1985.

On March 16, 1955, the United States Air Force officially ordered the development of an advanced reconnaissance satellite to provide continuous surveillance of “preselected areas of the earth” in order “to determine the status of a potential enemy’s war-making capability.”^[3]

Examples of reconnaissance satellite missions:

High resolution photography (IMINT)
Communications eavesdropping (SIGINT)
Covert communications
Enforcement of nuclear test bans (see National Technical Means)
Detection of missile launches

Naval ELINT:
Samos F
Molniya SIGINT:
- Jumpseat
- Trumpet
Geosynchronous SIGINT:
Air Force Geosynchronous SIGINT:
Lacrosse/Onyx (RADINT)
Misty/Zirconic
Quasar
Vela
Key Hole (KH) series of imaging satellites:

Time period	Designation	Code name or Nickname	Optics	Notes
1959–1962	KH-1 to KH-3	Corona	Resolution: 7.5 m Focal length: 0.6 m	First series of US imaging spy satellites; photographs returned by film canister ejection. Each satellite carried a single panoramic camera.
1960–1962	–	Samos	Res: 30 to 1.5 m Foc len: 0.7 to 1.83 m	Most flights used radio to relay images; some film returns; probably cancelled due to poor-quality imagery.
1962-1963	KH-4	Corona	Resolution: 7.5 m	Film return. Two panoramic cameras.
1963-1969	KH-4A	Corona	Resolution: 2.75 m	Film return with two reentry vehicles and two panoramic cameras. Large volume of imagery.
1967-1972	KH-4B	Corona	Resolution: 1.8 m	Film return with two reentry vehicles and two panoramic cameras.
1961–1964	KH-5	Argon	Res: 140 m Foc len: 76 mm	Film return. Low-resolution, high coverage-area images used for mapping.
1963	KH-6	Lanyard	Res: 1.8 m Foc len: 1.67 m	Shortlived operation for imaging a specific site; used a camera from the Samos program; film return.
1963–1967	KH-7	Gambit	Res: 0.46 m	Film return with single reentry vehicle per launch.
1966–1984	KH-8	Gambit	Res: 0.5 m	Film return.
1971–1986	KH-9	Hexagon "Big Bird"	Res: 0.30 m	Film return with four or five reentry vehicles per launch.
cancelled	KH-10	Dorian		Manned Orbital Laboratory; space station based on Gemini program.
1976–1995	KH-11	Crystal Kennan	Res: 0.15 m Mirror: 2.3 m	First known digital imaging spy satellite. Thought possibly to be similar in size and overall layout to the Hubble Space Telescope.
1990—?	KH-12	Ikon Improved Crystal	Res: 0.15 to 0.10? m Mirror: 2.4 to 4? m	Digital imaging; probably incorporates low light level visible and 3 to 5 micrometre infrared imaging capabilities; possible "live" intelligence gathering.
1999—?	KH-13	8X? EIS?	Res: 0.10? to 0.04? m (*) Mirror: 4? m	Very little known; possibly includes radar imaging or maybe stealth technology.

(*) Although there is much speculation concerning imaging resolution, any optical system is limited by diffraction. For example, a satellite with a 4m telescope at an orbit of 600km has a diffraction limited resolution of 10cm at 550nm (green light), so it certainly cannot read a license plate. Other effects such as an inhomogenious atmosphere further degrade resolution.