| Yantar-4KS1 | ||
The Yantar-2K was not capable of providing strategic warning of attack. Therefore three additional variants were developed, one of them the detailed electro-optical and operational reconnaissance satellite Yantar-4KS. A resolution of the chief designers dated 1 July 1977 began work on the project; this was confirmed by decree # 7-3 of the Soviet Ministers and Communist Party Central Committee dated 4 January 1978. The spacecraft was designed to relay visual and infrared band images via a digital data link to the planned Potok-Luch GKRSS satellite system. There were two phases to the project plan. The first phase spacecraft, the Yantar-4KS1, would be launched by the Soyuz-U2 launch vehicle, begin flight trials in 1979, with the system to be accepted into the military by 1981. Phase 2 would be the more capable Yantar-4KS2, launched by the more powerful Zenit launch vehicle, with flight trials to begin in 1983. Development was slow because of the state of Soviet digital electronics technology. The structure and wire harnesses for the first spacecraft were completed in 1978, but delays in the electronics meant that flight trials could not begin until the end of 1982. But the very first trials flight, in conjunction with the first Potok communications relay satellite, proved the worth of the system, with immediate operational use of the imagery. Yantar-4KS1 was accepted into military service in 1985. On 1 June 1983 the Yantar-4KS2 was cancelled and it was decided to modernize the Yantar-4KS1 instead. Flight trials of the improved model began in 1986, with flight times of 238 and 259 days, versus the maximum 207 days of the unimproved version. Further changes were an evolutionary process, with each satellite flown having improved technical characteristics and longer service life. After the fall of the Soviet Union, the satellites were being operated for over a year before having their mission terminated, despite a switch from the Soyuz-U2 to the less capable Soyuz-U launch vehicle. Typical orbital profile of the satellites was: inclination 64.9 degrees with an altitude of 230-280 km or 180-270 km. Typical orbit: 255 km circular orbit, 64.6 deg inclination. Mass: 6,620 kg (14,590 lb). Associated Launch Vehicle: Soyuz 11A511U, Soyuz 11A511U2. Yantar-4KS1 Chronology
Bibliography and Further Reading
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