Samos (satellite)

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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 from Vandenberg Air Force Base.

SAMOS was also known by the unclassified terms Program 101 and Program 201.[2]

History and costs[edit]

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 2015). For Samos, AF and ARPA spent a combined sum of US $82.9 million in FY1959 (inflation adjusted US$0.67 billion in 2015) and US $163.9 million in FY1960 (inflation adjusted US$1.31 billion in 2015).[3]

During this period, the rival CORONA program, which saw its first launch in February 1959, began operation. Samos emerged as a more advanced satellite with additional capabilities that due to its larger mass would be launched on the Atlas-Agena booster instead of the Thor-Agena. While CORONA took photographs and returned them to Earth in a film capsule, Samos would instead electronically scan its film and beam images down.

The first Samos launch took place from SLCW 1-1 at Point Arguello Launch Complex (later absorbed into the main launch center at Vandenberg Air Force Base) on October 11, 1960. Atlas performance was nominal, but after Agena separation and staging, the launch vehicle began tumbling and reentered the atmosphere, ending its flight in the Pacific Ocean rather than orbit. Postflight analysis found that a pad umbilical failed to detach properly at liftoff, allowing the Agena's nitrogen pressure gas to escape. The stage was left without any attitude control and could not be stabilized properly for main engine start.

Samos 2 was launched on January 31, 1961 and more-or-less accomplished its mission objectives although the electro-optical camera system produced rather mediocre results. After a month in orbit, the satellite exhausted its attitude control gas and was shut off. It decayed into the atmosphere in 1971.

The next attempt did not take place for nine months, in part because of the switch to the larger Agena B stage which could be restarted in orbit. Samos satellites after Samos 2 also sported a large "mushroom cap" nose cone as early plans had envisioned flying a manned capsule similar to Mercury. When it finally happened, the result was a complete disaster. Samos 3 lifted from SLCW 1-1 on September 9, but the Atlas booster's engines shut down at 2-inch motion and it fell back onto the pad in a fiery explosion. Cause of the accident was a pad umbilical that detached 0.21 seconds too late, causing the launch vehicle to switch from internal to external power.

Samos 3 was the last of the Program 101/101A satellites and the ambitious, but premature attempt at digital photography was abandoned and would not be tried successfully until the KH-11 satellites 20 years later. After this, Samos switched to a more conventional film recovery capsule. While the 101/101A satellites separated from the Agena in orbit, the 101B would remain attached and use it for orbital maneuvers and also deorbiting the film capsule at the end of the mission.

As it turned out, SLCW 1-1 was not seriously damaged by the explosion of Samos 3's booster and repair work only consisted of plumbing and electrical equipment, replacing the launcher mechanism, and cleaning and repainting. By October 29, the pad was fully restored to working condition and on November 22, Samos 4, the first Program 101B satellite, lifted off. Unfortunately, the launch was another failure, albeit less dramatic than Samos 3. The Atlas suffered a guidance malfunction at T+245 seconds into launch that resulted in loss of pitch control. This did not prevent the sustainer engine from functioning normally and the booster completed its burn on time, followed by staging. However, the Atlas had pitched up about 160 degrees leaving the Agena oriented in the wrong direction so that when its engine fired, it reentered the atmosphere and broke up over the Pacific Ocean.

Samos 5 was launched on December 22, but the Atlas malfunctioned yet again. This time, the sustainer engine did not cut off on schedule and continued operating until LOX depletion, putting the satellite into a high orbit which resulted in the deorbit maneuver failing. The capsule separated and reentered the atmosphere on January 9. Samos 6 (March 6, 1962) finally had no booster problems, but the satellite's onboard attitude control system malfunctioned and ran out of propellant by the 22nd orbit. When the Agena stage fired for the deorbit maneuver, Samos 6 was launched into a high orbit instead where it remained until reentering 15 months later. At this point, the idea of the recoverable capsule was abandoned and the electro-optical system put back into use. It proved no more successful than before and after another five Samos launches, the program was terminated.

In addition, a side program was operated during this period (Program 102) which launched a modified Samos on the Thor-Agena with no cameras at all, but instead electronic monitoring equipment for detecting Soviet missile launches (what could be described as an early ELINT satellite). Four of these were launched during 1962-63 with one failure when the first satellite's Agena failed to restart in orbit. The standard Samos apparently also carried ELINT subsatellites which remained attached to the Agena stage.

Meanwhile, in November 1961, President Kennedy issued an executive order placing all Department of Defense space programs under strict secrecy. The initial DoD launches in 1959-61 were not quite secret, in part because President Eisenhower doubted the ability of the US military to keep a secret for very long. The existence of CORONA, Midas, and Samos were publicly acknowledged even if the DoD was evasive about their exact purpose, generally using cover stories like the programs being for scientific studies.

However, Kennedy took a more rigid view of secrecy than his predecessor and all DoD programs from late 1961 onward were considered classified and top-secret. In any case, it was becoming increasingly difficult to explain to the public why these alleged scientific missions did not seem to be returning any data. Eventually, by 1963, the DoD did not officially acknowledge the existence of any space programs.

Vehicle missions[edit]

Mission chart from Zianet[4] and Astronautix.[5]
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 Improper disconnect of one of the pad umbilicals at liftoff resulted in nitrogen pressure gas escaping from the Agena and attitude control failure following staging
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 Pad umbilical disconnect 0.21 seconds later than intended. The Atlas lost electrical power and fell back onto the pad, exploding.
Samos 4 Nov. 22, 1961 1,860 -------- -------- -------- 1961-F13, NNN6101 Atlas attitude control failure at T+247 seconds leaving the booster oriented in the wrong direction. The Agena could not attain orbital velocity and fell into the Pacific Ocean.
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

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.[4] and Wade[5]
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.[6]

Recovery by Soviets[edit]

Section data from Wade.[5]

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.

See also[edit]


  1. ^ a b Gerald K. Haines (1997). "Development of the GAMBIT and HEXAGON Satellite Reconnaissance Systems". National Reconnaissance Office. 
  2. ^ Jonathan McDowell. "The history of spaceflight: SAMOS". Retrieved 2007-06-09. 
  3. ^ "Chronology of Air Force space activities". National Reconnaissance Office. 
  4. ^ a b The High Ground - SAMOS
  5. ^ a b c Wade, Mark, Encyclopedia Astronautica Samos
  6. ^ Walker, D. M. C., Samos 2 (1961 alpha 1): Orbit determination and analysis at 31:2 response (abstract), 02/1980