Cosmos 1603 was a Soviet ELINT (Electronic and Signals Intelligence) satellite launched from the Baikonur cosmodrome aboard a Proton rocket.
Based on the first generation Tselina ELINT, TSNII-KS at the beginning of the 1970's developed the specifications for an improved model with increased frequency range and on-board method of determining the position of fixed transmitters. The Tselina-2 was authorised in March 1973 and handled by prime contractor TsNIRTI Minradioprom (M E Zaslovskiy) for the ELINT equipment and KB Yuzhnoye (KB-3, B S Khimrov) for the spacecraft bus. The launch vehicle was by OKB MEI Minvuza (A F Bogomolov) and the encrypted communications system by 0-TsNII KS MO. The draft project was drawn up in the first quarter of 1974 and the MO approved the TTZ in May 1974. After a long review process the VPK issued the project plan for development of the system in December 1976. It would now use the new Zenit launch vehicle. The first flight trials system was completed in December 1980, but delays in the development of the Zenit launch vehicle meant that the first two trials flights had to be aboard Proton boosters in 1984 and 1985. Zenit-boosted flights began in 1985 and the system was accepted into service in 1987.
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