Zenit ( satellite ) Zenit ( , , " Zenith " ) was a series of military photoreconnaissance satellites launched by the Soviet Union between 1961 and 1994 . To conceal their nature , all flights were given the public Kosmos designation . Over a 33 year period , over five hundred Zenits were flown making it the most numerous type of satellite in the history of spaceflight . Description . The basic design of the Zenit satellites was similar to the Vostok manned spacecraft , sharing the return and service modules . It consisted of a spherical re - entry capsule 2 . 3 m in diameter with a mass of around 2400 kg . This capsule contained the camera system , its film , recovery beacons , parachutes and a destruct charge . In orbit , this was attached to a service module that contained batteries , electronic equipment , an orientation system and a liquid fuelled rocket engine that would slow the Zenit for re - entry , before the service module detached . The total length in orbit was around 5 m and the total mass was between 4600 kg and 4740 kg . Unlike the American Corona spacecraft , the return capsule carried both the film and the cameras and kept them in a temperature controlled pressurised environment . This simplified the design and engineering of the camera system but added considerably to the mass of the satellite . An advantage was that cameras could be reused . Early Zenits were launched using the Vostok rocket ; later versions used the Voskhod and the Soyuz rockets . The first flights were launched from Baikonur Cosmodrome but subsequent launches also took place at Plesetsk Cosmodrome . Most Zenits flew in a slightly elliptical orbit with a perigee of around 200 km and an apogee between 250 km and 350 km ; the missions usually lasted between 8 and 15 days . History . In 1956 , the Soviet government issued a secret decree that authorised the development of ' Object D ' which led to the program to launch Sputnik 3 ( Sputnik 1 was a simplified spin - off of the Object D program . ) The text of the decree remains secret , but it apparently authorised another satellite program – ‘ Object OD - 1 ’ – which was to be used for photo - reconnaissance from space . By 1958 , the OKB - 1 design bureau was simultaneously working on Object OD - 1 and Object OD - 2 - an early design for the Vostok manned spacecraft . The development of Object OD - 1 was experiencing serious difficulties so the head of OKB - 1 , Sergei Korolev , initiated work to see if a design based on Object OD - 2 could be used for an unmanned photo - reconnaissance satellite . This may have been a political manoeuvre that would enable him to continue the manned space program and avoid diverting more of OKB - 1 ’ s resources into Object OD - 1 . Despite bitter opposition from the military , the Soviet government endorsed Korolov ’ s approach and issued decrees on 22 and 25 May 1959 that ordered the development of three different spacecraft , all based on the same basic , Object OD - 2 , design . Spacecraft 1K would be a simplified prototype , 2K was to be a reconnaissance satellite and 3K was to be for manned flights . The name " Vostok " was also initially used for all three of these craft . But in 1961 the name became publicly known as the name of Yuri Gagarin ' s spacecraft so the ' Vostok 2 ' reconnaissance satellite was renamed ' Zenit 2 ' . The first Zenit launch attempt took place on 11 December 1961 , but there was a fault in the rocket ’ s third stage and the spacecraft was destroyed using its destruct charge . The second attempt — publicly referred to as Kosmos 4 — was successfully launched on 26 April 1962 and re - entered three days later . However a failure in the orientation system meant few useful pictures were obtained ; usable pictures had a resolution of about 5 to 7 meters . Launch # 3 on June 1 failed dramatically when the one of the 8A92 booster ' s strap - ons shut down at liftoff and fell onto the pad , exploding on impact . The rest of the launch vehicle crashed 300 meters away . This accident caused considerable damage to LC - 1 , delaying the flights of Vostok 3 and Vostok 4 by two months . On July 28 , LC - 1 was back in service to host the next Zenit flight , which performed successfully . Testing continued over the next year largely without incident , but on July 10 , 1963 another launch accident occurred in practically identical fashion to the June 1962 failure . Once again , one of the strap - ons shut down at liftoff , separated from the booster , and exploded on impact with the pad while the rest of the launch vehicle crashed a few hundred feet away . Examination of telemetry from the booster indicated that some sort of electrical failure occurred , but subsequent investigation took three months and finally concluded that a switch designed to cut power to the strap - ons at staging had malfunctioned , possibly due to liftoff - induced vibration . The electrical circuit in the 8A92 was redesigned and it never again experienced problems with the strap - ons shutting down at launch . Many versions of the satellite were developed for different reconnaissance missions and flights continued until 1994 . Zenit variants . Zenit 2 . Zenit 2 was the first version to be launched in 1961 ( there was no Zenit 1 . ) The arrangement of cameras varied , but most flights carried four cameras of 1000 mm focal length , and one of 200 mm focal length . The single lower resolution camera was intended to provide low - resolution pictures that would help give a context to the high - resolution pictures . Each camera had 1500 frames of film and from 200 km , each frame held an image of a 60 km by 60 km square . The ground resolution was stated to be 10 – 15 m although some unofficial sources claim it was much better — one source claims the number of cars in a car park could be counted . The cameras were developed at the Krasnogorsk Optical - Mechanical factory near Moscow . Curiously , this was also where the popular Zenit SLR cameras were made . Zenit 2s also carried ELINT equipment called Kust - 12M ( bush ) to receive NATO radar signals . The satellites carried a parabolic antenna , around 1 meter in diameter , that is associated with this equipment . However , it is unclear if the antenna transmitted recorded signals to the ground or was for intercepting radar signals . In the latter case they would have been recorded on magnetic tape , to be retrieved after the return capsule landed . There were 81 Zenit 2 launches , 58 were successful and 11 were partially successful . There were 12 failed missions , 5 because of a satellite malfunction and 7 because of a failure in the launch vehicle . First flight – Kosmos 4 , 1962 . Last flight – Kosmos 344 , 1970 . Zenit 2M . Improvements included a new camera system and the addition of solar panels . As the spacecraft mass was increased to 6300 kg , the Vostok rocket was replaced by the Voskhod and Soyuz rockets . In common with Zenit 2 satellites this also had an ELINT payload . First flight – Kosmos 208 , 1968 . Last flight – Kosmos 1044 , 1978 . Zenit 4 . Unlike Zenit 2 , little information on Zenit 4 has been released . The Zenit 4 was intended for high resolution photography and carried one camera of 3000 mm focal length as well as a 200 mm camera . The focal length of the main camera was greater than the diameter of the capsule so the camera made use of a mirror to fold the light path . The ground resolution is not publicly known but it is believed to have been 1 – 2 m . The Zenit 4 had a mass of 6300 kg — around 1500 kg more than the Zenit 2 . So , instead of the Vostok rocket , it was launched by the heavier Voskhod rocket . A probable total of 76 Zenit 4 ’ s were flown . First flight – Kosmos 22 , 1963 . Last flight – Kosmos 355 , 1970 . Zenit 4 M . An improved version of the Zenit 4 , the Zenit 4M carried a new camera , solar panels , and a restartable engine so the satellite ’ s orbit could be altered during the course of its mission . Mission duration was 13 days . First flight – Kosmos 251 , 1968 . Last flight – Kosmos 667 , 1974 . Zenit 4 MK / Zenit 4 MKM . These may have been versions of the Zenit 4 designed specifically to fly in lower orbits to improve image resolution . Some sources claim they were fitted with devices to compensate for aerodynamic drag and to withstand the effects of aerodynamic heating . First flight – Kosmos 371 , 1970 . Last flight – Kosmos 1214 , 1980 . Zenit 4 MT . A special version of the Zenit 4M intended for topographical photography . It carried a SA - 106 topographic camera , a laser altimeter and Doppler apparatus . First flight – Kosmos 470 , 1971 . Last flight – Kosmos 1398 , 1982 . Zenit 6U . A ‘ universal ’ version of the Zenit , intended for both low - altitude , high - resolution missions and higher - altitude , general observation missions . All flights used the Soyuz launch vehicle . There were 96 launches . First flight – Kosmos 867 , 1976 . Last flight – Kosmos 1685 , 1985 . Zenit 8 . This was intended for military cartographic photography . It used a Soyuz launch vehicle and launches took place from both Baikonur and Plesetsk . It had a 15 day orbital life . Similar satellites were referred to using the ‘ Resurs ’ designation . Kosmos 2281 , was the last Zenit flight . First flight – Kosmos 1571 , 1984 . Last flight – Kosmos 2281 , 1994 . Following the end of the programme , one Zenit - 8 satellite was launched on the maiden flight of the Soyuz - 2 rocket , as a DemoSat . The satellite was placed on a sub - orbital trajectory , and intentionally impacted the Pacific Ocean shortly after launch .