ManufacturerNPO Lavochkin
Country of origin Soviet Union
ApplicationsMissile defence
BusUpravlyaemy Sputnik
Launch mass2,400 kilograms (5,300 lb)
FailedNone known
Maiden launchKosmos 775
8 October 1975
Last launchKosmos 2345
14 August 1997
Related spacecraft
Derived fromUS-K

Upravlyaemy Sputnik Kontinentalny Statsionarny (Russian: Управляемый Спутник Континентальный Стационарный meaning Stationary Continental Controllable Satellite), or US-KS (Russian: УС-КС), also known as Oko-S, was a series of Soviet, and later Russian, missile detection satellites launched as part of the Oko (Russian: "eye") programme.[1] US-KS was a derivative of the US-K satellite, optimised for operations in geosynchronous orbit. Seven were launched between 1975 and 1997, when launches ended in favour of the modernised US-KMO.[2] US-KS had the GRAU index 74Kh6. As of December 2015, the entire Oko programme is being replaced by the new EKS system.[3]

Manufactured by NPO Lavochkin, US-KS satellites had a launch mass of 2,400 kilograms (5,300 lb), and a dry mass of 1,250 kilograms (2,760 lb). Built on a three-axis stabilised cylindrical bus with a diameter of 1.7 metres (5 ft 7 in) and a length of 2 metres (6 ft 7 in), the satellites carry 50 centimetres (20 in) infrared telescopes to detect the heat of missile exhausts.[4]

US-KS satellites were launched by Proton-K carrier rockets, with Blok DM and DM-2 upper stages. The first satellite to be launched was a prototype, which was followed by six operational spacecraft. With a spacecraft positioned at a longitude of 24° West, the Soviet Union could continuously monitor missile launches from the United States.[4]


  1. ^ Zak, Anatoly. "Oko early-warning satellite". RussianSpaceWeb. Retrieved 6 March 2012.
  2. ^ Krebs, Gunter. "US-KMO (71Kh6)". Gunter's Space Page. Retrieved 6 March 2012.
  3. ^ "Soyuz 2-1B launches EKS-1 to upgrade Russian Early Warning System". 17 November 2015. Retrieved 2015-12-17.
  4. ^ a b Krebs, Gunter. "US-KS (74Kh6)". Gunter's Space Page. Retrieved 6 March 2012.