In 1967, OKB-1 developed an experimental design of a new spacecraft called Yantar-2K intended for detailed imaging.
The construction of Yantar-2K consisted of three modules: the service module, the instrument module, and the reentry module with special hardware. On flanks of the reentry module there were two descent capsules mounted opposite each other for quick delivery of films to the Earth. Yantar-2K was of 2.7 m maximum diameter, 6.3 m in height and 6.6 tons in weight. The flight was calculated for 30 days. In 1968, the descent capsule intended for periodic delivery of films to the Earth was developed. The Yantar-2K space system was put into regular operation in accordance with the resolution of TsK KPSS and SM USSR on May 22, 1978.*
Advanced optical and photochemical manufacturing sciences in the end of 1970s made it possible for revolutionary modernization of the Yantar-2K SC. As a result, unique performance characteristics of the whole system were reached. The new Yantar-4K1 SC with service lifetime of 45 days outwardly practically did not differ from the Yantar-2K SC. Distinctions consisted only in some service and special systems. The first launch of the Yantar-4K1 SC took place on April 27, 1979. Operational flights began in 1982. Last flight of the spacecraft of Yantar type took place on November 30, 1983. Yantar spacecraft were replaced by enhanced satellites.*
* The article was written based on the materials taken from book - Spacecraft building:research and development by JSC SRC «Progress» edited by A.N.Kirilin- Samara: Publishing House, AGNI, 2011-p.280.