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Artist impression of SAMOS photoreconnaissance mission

The Samos E or SAMOS (Satellite and Missile Observation System) program was a relatively short-lived series of reconnaissance satellites for the United States in the early 1960s, also used as a cover for the initial development of the KH-7 Gambit system.[1] Reconnaissance was performed with film cameras and television surveillance from polar low Earth orbits with film canister returns and transmittals over the United States. Samos was first launched in 1960, but not operational until 1963 and all were launched from Vandenberg Air Force Base.[2]

SAMOS was also known by the unclassified terms Program 101 and Program 201.[3]

History and costs

SAMOS launch by an Atlas booster

Samos started as part of the WS-117L satellite reconnaissance and protection program of the US Air Force in 1956. In May 1958 the Department of Defense directed the transfer of the WS-117L program to ARPA. Significant parts of the Samos development program were Samos-E (visual reconnaissance), Samos-F (ELINT Ferret reconnaissance), and Samos-H (communications).[1]

In FY1958 WS-117L was funded by the AF at a level of US $108.2 million (inflation adjusted US$ 0.88 billion in 2022). For Samos, AF and ARPA spent a combined sum of US $82.9 million in FY1959 (inflation adjusted US$0.67 billion in 2022) and US $163.9 million in FY1960 (inflation adjusted US$1.31 billion in 2022).[4]


Section data from Yenne.[2]
  • Launch vehicles: Atlas Agena A,[5] Agena B[6] (early), Titan3B (later)
  • Vehicle weights: 4,100 pounds (early), 6,600 pounds (later)
  • Diameter: 58.5 inches
  • Classification: Dept. of Defense classified, IMINT
  • Launch site: Vandenberg AFB

Vehicle missions

Mission chart from Zianet[7] and Astronautix.[8]

Name Launch date Mass (kg) Perigee (km) Apogee (km) Inclination (deg) NSSDC ID Comments
Samos 1 Oct. 11, 1960 1,845 -------- -------- -------- 1960-F13, SAMOS-1 Launch Failure; satellite destroyed
Samos 2 Jan. 31, 1961 1,900 474 557 97.4 1961-ALPHA-1, 1961-001A First generation photo surveillance; radio relay of

images; micrometeroid impact data. Decayed 10/21/71

Samos 3 Sept. 9, 1961 1,150 -------- -------- -------- 1961-F09, SAMOS-3 Exploded on launch pad
Samos 4 Nov. 22, 1961 1,860 -------- -------- -------- 1961-F13, NNN6101 Failed to orbit
Samos 5 Dec. 22, 1961 1,860 244 702 89.6 1961-ALPHA-LAMBDA-2, 1961-035A Decayed 8/14/62
Samos 6 March 7, 1962 1,860 251 676 90.9 1962-ETA-3, 1962-007A Decayed 6/7/63
Samos 7 April 26, 1962 1,588 203 204 92.0 1962-PI, 1962-016A Decayed 4/28/62
Samos 8 June 17, 1962 1,860 -------- -------- -------- 1962-PSI, 1962-023A Decayed 6/18/62
Samos 9 July 18, 1962 1,860 184 236 96.1 1962-ZETA, 1962-030A Decayed 7/25/62
Samos 10 August 5, 1962 1,860 205 205 96.3 1962-ALPHA-LAMBDA, 1962-035A Decayed 8/6/62
Samos 11 November 11, 1962 1,860 206 206 96 1962-BETA-PI, 1962-064A Decayed 11/12/1962
Samos 87 March 1, 1972 unk unk unk unk unk DOD launch classified.[2]

From October 1960 to November 1962, at least 11 launch attempts were made. Portions of the program are still considered classified information. It is believed that the program was cancelled because the imagery produced was poor. The program was operated by the United States Air Force, but was overshadowed by the CIA's Corona program.

At least two different generations of the satellite were made, and at least four different types of cameras were used. Early on, the idea was to use frame readout cameras that would take a picture and send the scanned image via radio to ground stations on Earth. This system was apparently troublesome, so the program also developed a photographic film return system where the camera and used film would be ejected and be retrieved as it floated down through the atmosphere by parachute. Film-return satellites would remain the standard until the KH-11 satellite with digital imaging capability emerged in the 1970s.


Equipment chart from Zianet.[7] and Wade[8]
Name Type Focal Length Resolution Swath
E-1 readout 1.83 m (72 in) 30 m (100 ft) 161 × 161 km
E-2 readout 0.91 m (36 in) 6 m (20 ft) 27 × 27 km
E-5 film 1.67 m (66 in) 1.5 m (5 ft) 98 km length
E-6 film 0.7 m (28 in) 2.4 m (8 ft) 280 km width

The E-1 and E-2 cameras used the readout method. Little is known about the E-3 type of camera, which was eventually cancelled. It likely had higher resolution, and may have been superseded by the later E-6. An E-4 camera was initially planned for relatively low-resolution mapmaking purposes, but it was cancelled with the functionality being taken up by the KH-5 (Argon) satellite. The E-5 and E-6 were panoramic format film cameras that appeared in later launches, but only a few were used. The E-5 would later be called upon in the short-lived KH-6 (Lanyard) program.

Some satellites were equipped with so-called Ferret devices, for "ferreting" information by spying on electronic communication. A more modern term for that activity would be Signals Intelligence. Toward the end of the program, satellites were only being launched with Ferrets, without any cameras. Two Ferret systems were created, designated F-1 and F-2.

Some additional payloads were sometimes on board, mostly scientific devices for learning more about the space environment so that future satellites could be better-designed for spaceflight. The satellites as launched varied in mass from 1845 to 1900 kilograms.


Samos-2 was the first satellite to enter a sun-synchronous orbit.[9]

Recovery by Soviets

Section data from Wade.[8]

Sergei Khrushchev wrote in his memoirs about the partial recovery of what he believed was a Samos satellite, except the date was the winter before the program started. A second capsule was apparently recovered in early 1961, although the device had been disassembled by local farmers, exposing film and preventing the Soviets from determining the satellite's capabilities. It may or may not have been a Samos.


  1. 1.0 1.1 Gerald K. Haines (1997). "Development of the GAMBIT and HEXAGON Satellite Reconnaissance Systems". National Reconnaissance Office.  Cite error: Invalid <ref> tag; name "SAMOS_Program" defined multiple times with different content
  2. 2.0 2.1 2.2 Yenne, Bill (1985). The Encyclopedia of US Spacecraft. Exeter Books (A Bison Book), New York. ISBN 0-671-07580-2. p.130 SAMOS
  3. Jonathan McDowell. "The history of spaceflight: SAMOS". Retrieved 2007-06-09. 
  4. "Chronology of Air Force space activities". National Reconnaissance Office. 
  5. SAMOS on Agena A A drawing
  6. SAMOS on Agena B A drawing.
  7. 7.0 7.1 The High Ground - SAMOS
  8. 8.0 8.1 8.2 Wade, Mark, Encyclopedia Astronautica Samos
  9. Walker, D. M. C., Samos 2 (1961 alpha 1): Orbit determination and analysis at 31:2 response (abstract), 02/1980

See also

  • Dr. James Gilbert Baker

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