Zenit (satellite)

Zenit was a series of Soviet military photoreconnaissance satellites launched between 1961 and 1994, every flight being given the public name Kosmos to conceal its nature. The basic design resembled the Vostok crewed spacecraft and shared its return and service modules: a spherical re-entry capsule 2.3 metres across and about 2,400 kilograms in mass held the cameras, the film, recovery beacons and parachutes, and was joined in orbit to a service module with batteries, electronics and a liquid-fuelled rocket engine that slowed the satellite for re-entry. The whole craft was about five metres long and weighed between 4,600 and 4,740 kilograms. Unlike the American Corona, the capsule carried the cameras as well as the film, so the cameras could be reused. The first launch attempt on 11 December 1961 failed in the third stage, and Kosmos 4 reached orbit on 26 April 1962. Early flights used the Vostok rocket and later ones the Voskhod and Soyuz. Missions usually lasted eight to fifteen days.