The Russian Yantar-4K1 or Oktan series was the second generation of the high resolution film-return variant of the Yantar reconnaissance satellite series.
This series was a minor improvement over the Yantar-2K (Feniks) series, with prolonged lifetime and improved camera system.
These satellites were developed by TsSKB Progress, Samara, and were built at OAO Arsenal, St Petersburg. They consisted of a service module with reignitable propulsion and two solar arrays, a large conical reentry vehicle with the camera and two small spherical reentry vehicles (SpK, Spuskayemaya Kapsula). The launch mass was about 6700 kg. The orbital life time was up to 45 days. They carried the Zhemchug-18 camera system in the main return capsule, which allowed the camera system and the board computer to be reused. The return capsules could be reused up to three times.
The satellites were launched by Soyuz-U from Plesetsk and Baikonur, typically into a 170 km by 350 km orbit with inclinations between 62.8° and 67.2°. The typical landing area was near Orenburg.
The Yantar-4K1 series introduced in 1979 and continued until it was phased out in 1983, with the improved Yantar-4K2 (Kobalt) satellites gradually taking over since 1981.
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