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 United States 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 Air Force at a level of US$108.2 million (inflation adjusted US$ 0.90 billion in 2017). For Samos, AF and ARPA spent a combined sum of US$82.9 million in FY1959 (inflation adjusted US$0.68 billion in 2017) and US$163.9 million in FY1960 (inflation adjusted US$1.33 billion in 2017).[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 by radio link.

Although "Samos" was the name of a Greek island, the satellite's name actually consisted of an abbreviation for the clumsy phrase "Satellite And Missile Observation System", a completely misleading name designed to cover up the real purpose of the program. In any case, President Eisenhower was adamant about cultivating the image that the US space program was only for peaceful purposes. The Air Force for a while managed to create the fiction that Discoverer was a series of scientific satellites, but Samos's real purpose was known from the beginning, and efforts to not link it to Discoverer were made.

While Corona began flying in 1959, the reliability of the program for its first three years was abysmal and a backup reconnaissance program was needed. Moreover, the phobia of the "Missile Gap" with the Soviet Union was very great, with space successes and boasts by Soviet politicians seeming to hint that the USSR not only had a large arsenal of nuclear missiles on hand, but were quite willing to use them. The US ballistic missile arsenal in 1960 consisted of a handful of Atlas ICBMs that were exposed to Soviet attack, took a long time to prepare for launch, and whose test flight record did not inspire much confidence. The Thor and Jupiter IRBMs stationed in the UK, Italy, and Turkey were not much of an improvement, also their bases could be attacked by Soviet bombers. Intelligence on Soviet missile activities was considered vital, but the only viable option, U-2 reconnaissance flights, had been halted by the Gary Powers shootdown in May 1960. Unbeknownst to the Pentagon, Soviet missiles were deployed in far smaller numbers than generally believed and their reliability was no better than any US missile.

The initial Samos satellites were known as Program 101 and were merely a test model designed to verify the operability of the photo-optical camera system. The first Samos launch took place from PALC 1-1 at Point Arguello Launch Complex (later absorbed into the main launch center at Vandenberg Air Force Base) on October 11, 1960. During ascent, the Atlas guidance system failed, but the flight control system kept the vehicle on a stable flight path. Since the guidance system was not telemetered on this launch, a reason for the failure could not be determined. 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 at liftoff and was ripped out of the Agena as the booster lifted off the pad, allowing its nitrogen pressure gas to escape. The stage was left without any attitude control and could not be stabilized properly. In addition, the pneumatic system apparently suffered damage as Agena engine performance was below normal due to lack of pressure in the fuel feed system. As it turned out, a technician had made the simple mistake of not properly securing a lanyard on one of the pad umbilicals. Film and photographs of Samos 1's launch clearly showed a cloud of escaping nitrogen gas from the Agena.

Samos 2 was launched on January 31, 1961 and more-or-less accomplished its mission objectives, although the electro-optical camera system produced only 100 feet of resolution, hardly enough for serious reconnaissance. 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, because of the switch to the larger Agena B stage that could be restarted in orbit and the operational Program 101A satellites, which had a more advanced camera system with better resolution and a wider field of view. 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 PALC 1-1 on September 9, but the Atlas booster's engines shut down after the rocket had ascended 2 inches 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.

After Samos 3, it was decided to abandon the Program 101/101A satellites entirely and switch to a more conventional film recovery capsule, since the one successful mission had not proven the viability of the electro-optical camera system. While the 101/101A satellites separated from the Agena in orbit, the 101B would remain attached and would use it for orbital maneuvers and also deorbiting the film capsule at the end of the mission.

Several more 101/101A satellites were either completed or in a state of partial completion when the program was called off, but the problem of how to dispose of them was never satisfactorily solved. Most were left mothballed in warehouses or scrapped. There was talk of giving the camera systems to NASA for the planetary probe program, but they were of doubtful value for taking photographs of the Moon. The Agena stages that could not be repurposed for other programs were scrapped.

The 101B satellites were originally intended to use an encrypted communications system out of paranoia that the Soviets could not only intercept transmissions, but even reprogram the satellite to land on their territory. Unlike Corona, the 101B satellites would land with the complete camera system, not just the film capsule, and the Pentagon and State Department dreaded the consequences of a landing on Soviet territory. Ultimately, the encrypted communication requirement was dropped in October 1961, a mere month before the first 101B satellite launched.

As it turned out, PALC 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. Extensive efforts were made to ensure mission success, such as X-ray testing for bad transistors and super-clean propellant tanks. 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 drove the satellite into the Pacific Ocean.

The next two Program 101B satellites contained several technical improvements, such as more sophisticated telemetry and control/communications systems, and improved cameras.

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 (although given that reentry would have taken place over densely-populated New England, this was not necessarily a bad thing). The reentry command had activated all systems in the satellite, quickly draining the batteries. With the loss of electrical power, the parachutes could not be deployed during reentry, and also since the retrorockets had been expended during the failed deorbit maneuver, Samos 5 would only leave orbit once it decayed naturally. Without the parachutes or retrorockets, the capsule's descent would be far too fast for air recovery to be possible, but it could still easily survive reentry and land almost anywhere. The spent Agena stage reentered over Indonesia on December 31, and it was calculated that reentry of the satellite itself would happen on January 6.

When January 6 came, the indications were that Samos 5 impacted somewhere in northwestern Canada. An Air Force search party attempted to obtain Canadian permission to search the suspected area, but were unable to explain exactly what they were looking for. The Canadian authorities were suspicious that a B-52 aircraft had accidentally lost a nuclear warhead somewhere, and since this was not an easily resolved matter, the search was called off. Later on, a pair of U-2 reconnaissance aircraft searched the suspected area, but failed to locate any satellite debris.[4]

Samos 6 (March 6, 1962) finally had no booster problems, in part due to modifications made to the Agena after lessons learned from previous missions, but a series of erroneous ground commands caused the satellite to deplete its attitude control gas. When the Agena stage fired for the deorbit maneuver, Samos 6 was launched into a high orbit. In July 1963, fifteen months later, the satellite was on the verge of reentry. With the electrical system dead for months, there was again no chance of an air recovery of the capsule, but it could still survive reentry. However, it was calculated that impact would occur in the Arabian Sea and in all likelihood, the cold ocean water would crack the heat shield and cause it to sink. No attempt was made to recover Samos 6, which did apparently land in the Arabian Sea. 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. By the end of 1962, when the last Samos satellite flew, only the Corona program had managed to return usable reconnaissance images. The photos obtained by Samos 2 back at the start of 1961 were considered little more than curiosities, their resolution too low for reconnaissance. The Lanyard program had by this time emerged as a successor to Samos, and by 1962, Corona was at last reaching operational status.

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 from 1962 to 1963 with one failure when the first satellite's Agena failed to restart in orbit. The standard Samos apparently also carried ELINT subsatellites that remained attached to the Agena stage.

Like most early space programs, Samos had goals that exceeded what contemporary technology was capable of, and the launch vehicles used to orbit it were nearly as marginal as the satellite itself. Digital photography was not attempted successfully until the KH-11 satellites came online in the late 1970s.

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. One reason for the heightened secrecy was the fact that the Soviet Union by mid-1961 had begun accusing the US of engaging in reconnaissance from space.

Vehicle missions[edit]

Mission chart from Zianet[5] and Astronautix.[6]
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.[5] and Wade[6]
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.

E-1 camera, particularly the unique system of developing and scanning the film on orbit, was later adapted by Kodak for NASA moon cartographing Lunar Orbiter program.[7]

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.[8]

Recovery by Soviets[edit]

Section data from Wade.[6]

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" (PDF). National Reconnaissance Office.  Cite error: Invalid <ref> tag; name "SAMOS_Program" defined multiple times with different content (see the help page).
  2. ^ Jonathan McDowell. "The history of spaceflight: SAMOS". Retrieved 2007-06-09. 
  3. ^ "Chronology of Air Force space activities" (PDF). National Reconnaissance Office. 
  4. ^
  5. ^ a b The High Ground - SAMOS
  6. ^ a b c Wade, Mark, Encyclopedia Astronautica Samos
  7. ^
  8. ^ Walker, D. M. C., Samos 2 (1961 alpha 1): Orbit determination and analysis at 31:2 response (abstract), 02/1980