What is "okno-s"

Okno-S is a reported Russian military space surveillance facility used to identify and analyse the orbits of satellites and other space objects. If it is operational, it would be run by the Russian Aerospace Defence Forces and complement the Okno station in Nurak, Tajikistan. Very little is known about the facility, including its precise location. There has been speculation on the differences between Okno and Okno-S but there has been no confirmation from official sources.