Oko, is a Russian 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. The information provided by these sensors can be used for the A-135 anti-ballistic missile system which defends Moscow. The satellites are run by the Russian Aerospace Forces, and previously the Russian Aerospace Defence Forces and Russian Space Forces. As of December 2015, it is being replaced by the new EKS system.
