The Soviet RORSAT program, mentioned briefly above, began sporadic operations in October 1970, after two 1-day flight tests of spacecraft support systems in 1967 and 1968 (Kosmos 198 and Kosmos 209, respectively). Equipped with a nuclear-powered radar,the RORSAT spacecraft could reportedly detect destroyer-size ships in good weather and aircraft carrier-size vessels in rough seas, but submarine detection remained an elusive goal. The RORSAT program ceased flight operations in 1988 after five serious mishaps in 33 missions, including two nuclear reactors falling back to Earth from orbit and two launch failures.
The RORSAT spacecraft possessed some similarities with its EORSAT relation and was 3,800 kg in mass, 1.3 m in diameter, and 10 m in length. The nuclear reactor and high altitude storage system (needed to maneuver the reactor from its operational orbit of 250 km to a long-lived disposal orbit of 900-1,000 km) accounted for 1,250 kg and slightly more than half (5.8 m) the length of the spacecraft. The fuel assembly (53 kg, 0.6 m long, 0.2 m in diameter) consisted of 37 cylindrical fuel elements with 31.1 kg (beginning of life) of 90% U235 enrichments (Reference 80).
Following the reentry of Kosmos 954 over Canada in 1978, the RORSAT reactor underwent several modifications, including the ability to eject the fuel assembly at the end of life, hopefully in the disposal orbit but prior to reentry in the event of accident, e.g. Kosmos 1402 in in 1983. Between 1980 and 1988, at least 14 RORSATs did perform fuel assembly ejection in the higher altitude storage orbits. However, not until 1994 did terrestrial-based space surveillance sensors detect what may be large numbers of very small particles of NaK reactor coolant released when the fuel assembly was ejected (References 80-81).
80. Use of Nuclear Power Sources in Outer Space, Report A/AC.105/C.1/WG.5/L.24/Add.2, Committee on the Peaceful Uses of Outer Space, General Assembly, United Nations, 26 February 1990.
81. Nazarenko, , A.I., et al, "Analysis of Fragmentation Situation in the Neighborhood of Russian Satellites with Nuclear Power Sources", Orbital Debris Monitor, July 1995.