Zenit (Russian: Зени́т, IPA: [zʲɪˈnʲit], Zenith) was a series of military photoreconnaissance satellites launched by the Soviet Union between 1961 and 1994.

The basic design of the Zenit satellites was similar to the Vostok crewed spacecraft, sharing the return and service modules.

[1] It consisted of a spherical re-entry capsule 2.3 metres (7.5 ft) in diameter with a mass of around 2,400 kilograms (5,300 lb).

[1] Unlike the American CORONA spacecraft, the return capsule carried both the film and the cameras and kept them in a temperature-controlled pressurised environment.

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.

This may have been a political manoeuvre that would enable him to continue the crewed space program and avoid diverting more of OKB-1's resources into Object OD-1.

[1][3][4][5] Despite bitter opposition from the military the Soviet government endorsed Korolev's approach and issued decrees on 22 and 25 May 1959 which ordered the development of three different spacecraft, all based on the same basic, Object OD-2, design.

[6] 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.

Launch #3 on 1 June 1962 failed dramatically when one of the 8A92 booster's strap-ons shut down at liftoff and fell onto the pad, exploding on impact.

Testing continued over the next year largely without incident but on 10 July 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 Krasnogorsk factory, which had been producing a variety of optical equipment for the military since 1942, was also the manufacturer of the popular Zenit SLR cameras.

[1] Zenit 2s also carried ELINT equipment called Kust-12M (bush) to receive NATO radar signals.

[18][19] These may have been versions of the Zenit 4 designed specifically to fly in lower orbits to improve image resolution.