Yantar-4K1 ( meaning amber) was a type of Soviet reconnaissance satellite which supplemented and eventually replaced the Zenit spacecraft. It was the second satellite of the Yantar series and was managed by the Soviet military intelligence agency, the GRU. These satellites were in orbit for 45 days and photographed sites of interest using a film camera. It had its first test launch in May 1979. It was only in military service from 1982 to 1983, had the GRAU index 11F693 and was given the name Oktan (), meaning octane.