US-A (Upravlenniye Sputnik Aktivny) were active radar satellites for ocean surveillance. The high power consumtion of the active radar required a nuclear reactor as power source. The satellites were known as RORSAT in the west. The US-AO series consisted of satellites, which tested all the system components but the nuclear reactor. They were battery powered. December 27, 1965 at 22:24 UTC · Launch Successful Soyuz 11A510 — Soviet Space Program, to Low Earth Orbit 31/6, Baikonur Cosmodrome, Republic of Kazakhstan The world's 515th orbital launch attempt, and 122nd of 1965. Data: Launch Library 2, The Space Devs.