The KH-8 (BYEMAN codename Gambit-3) was a long-lived series of reconnaissance satellites of the "Key Hole" (KH) series used by the United States from July 1966 to April 1984, and also known as Low Altitude Surveillance Platform. The satellite ejected "film-bucket" canisters of photographic film that were retrieved as they descended through the atmosphere by parachute. Ground resolution of the mature satellite system was better than .
While Gambit was primarily designed and operated as a surveillance satellite, capturing high definition images of specific targets at low orbital altitudes, a single Gambit Block 3 mission was operated in 'dual-mode', orbiting first at a higher altitude to capture wide-area search imagery before lowering its perigee to capture normal surveillance imagery. The first film return capsule failed to separate correctly due to a new pyro mechanism failing to perform correctly. The contingency release mechanism separated the film bucket and parachute from its return capsule, and left the film bucket stranded in orbit. In September 2002, the film bucket re-entered over the South Atlantic into deep water. As the film bucket lacked its protective heatshield or the parachute needed to slow its descent, no attempt was made to recover it.
Camera Optics Module
thumb|KH-8 GAMBIT-3 Photographic Payload Section
thumb|KH-8 Photographic Payload Section
The Camera Optics Module of KH-8 consists of four cameras.
The main camera of KH-8B (introduced in 1971) with a focal length of is a single strip camera, designed to gather high-resolution images of ground targets. In the strip camera the ground image is reflected by a steerable flat mirror to a diameter stationary concave primary mirror. The primary mirror reflects the light through an opening in the flat mirror and through a Ross corrector. At periapsis altitude of , the main camera imaged a 6.3 km wide ground swath on a wide moving portion of film through a small slit aperture, resulting in an image scale of 28 meter / millimeter. The Astro-Position Terrain Camera (APTC) contains three cameras: a 75mm focal length terrain frame camera, and two 90mm focal length stellar cameras. The terrain frame camera takes exposures of Earth in direction of the vehicle roll position for attitude determination. The stellar cameras observed in 180 degree opposite directions and took images of star fields. Subsequent films used were Type 1414 high-definition film, SO-217 high-definition fine-grain film, and a series of films with silver-halide crystals of very uniform size and shape. The size of silver-halide crystals decreased from 1,550 angstrom in film Type SO-315, to 1,200 angstrom in SO-312, and ultimately to 900 angstrom in SO-409. Under optimal conditions GAMBIT would thus have been able to record ground features as small as using the Eastman Kodak Type 3404 film. Using a film with a resolving power equivalent to the Kodak's Type 3409 film of 320 to 630 line pairs per mm, GAMBIT would have been able to record ground features as small as 5 cm to 10 cm (2" to 4"). The initial September 2011 release of "The Gambit Story" quotes "The mature system produced examples of imagery better than four inches ground-resolution distance". This number was again redacted in a later release. and, independently, Evvard in the mid-1960s; remarkably, GAMBIT had reached a physical limit on resolution only a few years after the US launched its first reconnaissance satellite. GAMBIT was also able to record objects in orbit. The capability was developed to photograph Soviet spacecraft, but was first used to aid NASA engineers designing repairs for the damaged Skylab space station in 1973.
Missions
thumb|Ascent and Orbital events for GAMBIT-3 missions
thumb|[[N1 (rocket) imaged by KH-8 Gambit on 19 September 1968]]
thumb|KH-8 GAMBIT 3 (Block 1) main features
thumb|KH-8 GAMBIT 3 (Block 2) main features
thumb|KH-8 GAMBIT 3 (Block 3 & 4) main features
{| class="wikitable"
|-
! Name
! Block
! Launch Date
! Alt. Name
! NSSDC ID No.
! Launch Vehicle
! Orbit
! Decay date
|-
| KH8-1
| I
| 1966-07-29
| OPS-3014
| 1966-069A
| Titan IIIB
| 158.0 km × 250.0 km, i=94.1°
| 1966-08-06
|-
| KH8-2
| I
| 1966-09-28
| OPS-4096
| 1966-086A
| Titan IIIB
|
|
|-
| KH8-3
| I
| 1966-12-14
| OPS-8968
| 1966-113A
| Titan IIIB
|
|
|-
| KH8-4
| I
| 1967-02-24
| OPS-4204
| 1967-016A
| Titan IIIB
|
|
|-
| KH8-5
| I
| 1967-04-26
| OPS-4243
| 1967-F04, 1967-003X
| Titan IIIB
| no stable orbit
| 1967-04-26
|-
| KH8-6
| I
| 1967-06-20
| OPS-4282
| 1967-064A
| Titan IIIB
|
|
|-
| KH8-7
| I
| 1967-08-16
| OPS-4886
| 1967-079A
| Titan IIIB
|
|
|-
| KH8-8
| I
| 1967-09-19
| OPS-4941
| 1967-090A
| Titan IIIB
|
|
|-
| KH8-9
| I
| 1967-10-25
| OPS-4995
| 1967-103A
| Titan IIIB
|
|
|-
| KH8-10
| I
| 1967-12-05
| OPS-5000
| 1967-121A
| Titan IIIB
|
|
|-
| KH8-11
| I
| 1968-01-18
| OPS-5028
| 1968-005A
| Titan IIIB
|
|
|-
| KH8-12
| I
| 1968-03-13
| OPS-5057
| 1968-018A
| Titan IIIB
|
|
|-
| KH8-13
| I
| 1968-04-17
| OPS-5105
| 1968-031A
| Titan IIIB
|
|
|-
| KH8-14
| I
| 1968-06-05
| OPS-5138
| 1968-047A
| Titan IIIB
|
|
|-
| KH8-15
| I
| 1968-08-06
| OPS-5187
| 1968-064A
| Titan IIIB
|
|
|-
| KH8-16
| I
| 1968-09-10
| OPS-5247
| 1968-074A
| Titan IIIB
|
|
|-
| KH8-17
| I
| 1968-11-06
| OPS-5296
| 1968-099A
| Titan IIIB
|
|
|-
| KH8-18
| I
| 1968-12-04
| OPS-6518
| 1968-108A
| Titan IIIB
|
|
|-
| KH8-19
| I
| 1969-01-22
| OPS-7585
| 1969-007A
| Titan IIIB
|
|
|-
| KH8-20
| I
| 1969-03-04
| OPS-4248
| 1969-019A
| Titan IIIB
|
|
|-
| KH8-21
| I
| 1969-04-15
| OPS-5310
| 1969-039A
| Titan IIIB
|
|
|-
| KH8-22
| I
| 1969-06-03
| OPS-1077
| 1969-050A
| Titan IIIB
|
|
|-
| KH8-23
| II
| 1969-08-23
| OPS-7807
| 1969-074A
| Titan 23B
|
|
|-
| KH8-24
| II
| 1969-10-24
| OPS-8455
| 1969-095A
| Titan 23B
|
|
|-
| KH8-25
| II
| 1970-01-14
| OPS-6531
| 1970-002A
| Titan 23B
|
|
|-
| KH8-26
| II
| 1970-04-15
| OPS-2863
| 1970-031A
| Titan 23B
|
|
|-
| KH8-27
| II
| 1970-06-25
| OPS-6820
| 1970-048A
| Titan 23B
|
|
|-
| KH8-28
| II
| 1970-08-18
| OPS-7874
| 1970-061A
| Titan 23B
|
|
|-
| KH8-29
| II
| 1970-10-23
| OPS-7568
| 1970-090A
| Titan 23B
|
|
|-
| KH8-30
| II
| 1971-01-21
| OPS-7776
| 1971-005A
| Titan 23B
| 139.0 km × 418.0 km, i=110.8°
| 1971-02-09
|-
| KH8-31
| II
| 1971-04-22
| OPS-7899
| 1971-033A
| Titan 23B
| 132.0 km × 401.0 km, i=110.9°
| 1971-05-13
|-
| KH8-32
| II
| 1971-08-12
| OPS-8607
| 1971-070A
| Titan 24B
| 137.0 km × 424.0 km, i=111.0°
| 1971-09-03
|-
| KH8-33
| II
| 1971-10-23
| OPS-7616
| 1971-092A
| Titan 24B
| 134.0 km × 416.0 km, i=110.9°
| 1971-11-17
|-
| KH8-34
| II
| 1972-03-17
| OPS-1678
| 1972-016A
| Titan 24B
| 131.0 km × 409.0 km, i=111.0°
| 1972-04-11
|-
| KH8-35
| II
| 1972-05-20
| OPS-6574
| 1972-F03
| Titan 24B
| failed to reach orbit
|
|-
| KH8-36
| II
| 1972-09-01
| OPS-8888
| 1972-068A
| Titan 24B
| 140.0 km × 380.0 km, i=110.5°
| 1972-09-30
|-
| KH8-37
| III
| 1972-12-21
| OPS-3978
| 1972-103A
| Titan 24B
| 139.0 km × 378.0 km, i=110.5°
| 1973-01-23
|-
| KH8-38
| III
| 1973-05-16
| OPS-2093
| 1973-028A
| Titan 24B
| 139.0 km × 399.0 km, i=110.5°
| 1973-06-13
|-
| KH8-39
| III
| 1973-06-26
| OPS-4018
| 1973-F04
| Titan 24B
| failed to reach orbit
| (mix-up with KH8-38 in NSSDC)
|-
| KH8-40
| III
| 1973-09-27
| OPS-6275
| 1973-068A
| Titan 24B
| 131.0 km × 385.0 km, i=110.5°
| 1973-10-29
|-
| KH8-41
| III
| 1974-02-13
| OPS-6889
| 1974-007A
| Titan 24B
| 134.0 km × 393.0 km, i=110.4°
| 1974-03-17
|-
| KH8-42
| III
| 1974-06-06
| OPS-1776
| 1974-042A
| Titan 24B
| 136.0 km × 394.0 km, i=110.5°
| 1974-07-24
|-
| KH8-43
| III
| 1974-08-14
| OPS-3004
| 1974-065A
| Titan 24B
| 135.0 km × 402.0 km, i=110.5°
| 1974-09-29
|-
| KH8-44
| III
| 1975-04-18
| OPS-4883
| 1975-032A
| Titan 24B
| 134.0 km × 401.0 km, i=110.5°
| 1975-06-05
|-
| KH8-45
| III
| 1975-10-09
| OPS-5499
| 1975-098A
| Titan 24B
| 125.0 km × 356.0 km, i=96.4°
| 1975-11-30
|-
| KH8-46
| III
| 1976-03-22
| OPS-7600
| 1976-027A
| Titan 24B
| 125.0 km × 347.0 km, i=96.4°
| 1976-05-18
|-
| KH8-47
| III
| 1976-09-15
| OPS-8533
| 1976-094A
| Titan 24B
| 135.0 km × 330.0 km, i=96.4°
| 1976-11-05
|-
| KH8-48
| IV
| 1977-03-13
| OPS-4915
| 1977-019A
| Titan 24B
| 124.0 km × 348.0 km, i=96.4°
| 1977-05-26
|-
| KH8-49
| IV
| 1977-09-23
| OPS-7471
| 1977-094A
| Titan 24B
| 125.0 km × 352.0 km, i=96.5°
| 1977-12-08
|-
| KH8-50
| IV
| 1979-05-28
| OPS-7164
| 1979-044A
| Titan 24B
| 124.0 km × 305.0 km, i=96.4°
| 1979-08-26
|-
| KH8-51
| IV
| 1981-02-28
| OPS-1166
| 1981-019A
| Titan 24B
| 138.0 km × 336.0 km, i=96.4°
| 1981-06-20
|-
| KH8-52
| IV
| 1982-01-21
| OPS-2849
| 1982-006A
| Titan 24B
| 630.0 km × 641.0 km, i=97.4°
| 1982-05-23
|-
| KH8-53
| IV
| 1983-04-15
| OPS-2925
| 1983-032A
| Titan 24B
| 124.0 km × 254.0 km, i=96.5°
| 1983-08-21
|-
| KH8-54
| IV
| 1984-04-17
| OPS-8424
| 1984-039A
| Titan 24B
| 127.0 km × 235.0 km, i=96.4°
| 1984-08-13
|-
|}
<small>(NSSDC ID Numbers: See COSPAR)</small>
Notable Missions
In May 1973 Gambit KH8-38 was used to observe the crippled Skylab space station, as part of the preparation for repairing it by the Skylab 2 mission.