'Eye')[a] is a Russian (previously Soviet) missile defence early warning programme consisting of satellites in Molniya and geosynchronous orbits.
Oko satellites are used to identify launches of ballistic missiles by detection of their engines' exhaust plume in infrared light, and complement other early warning facilities such as Voronezh, Daryal and Dnepr radars.
[1] Development of the Oko system began in the early 1970s under the design bureau headed by AI Savin, which became TsNII Kometa.
[2] The system had a major malfunction in 1983 when it mistakenly identified sunlight on high altitude clouds as a missile attack.
The first generation Molniya-type orbit Oko satellites launched between 1976 and 1983 were prone to disintegration, resulting in extensive space debris.