Dunay radar

Dunay radar (Дунай literally Danube; NATO: Cat House, Dog House) was a system of two Soviet radars used to detect American ballistic missiles fired at Moscow. They were part of the A-35 anti-ballistic missile system. One sector of one of the radars, the Dunay-3U ("Cat House") is still operational and is run by the Russian Space Forces as part of the Main Control Centre of Outer Space.

Dunay-2
The Dunay-2 was a prototype built in Sary Shagan as part of the experimental missile defence system "A". It consisted of separate transmitter and receiver complexes separated by 1 km. The power of the radar was 100 kW and its range was 1200 km. The NATO codename was "Hen Roost".

Dunay-3M
The Dunay-3 (Дунай-3М; NATO: Dog House) was an upgrade of the Dunay-2 located in Kubinka, Moscow and became operational in 1968. Following an extensive upgrade in 1978 it was renamed Dunay-3M as part of the upgraded A-35M ABM system. It consisted of separate receiver and transmitter buildings separated by 2.5 km.

The transmitter covered two sectors (roughly north and south) and its array was 200 m long and 30 m high. The power of each sector was about $100 kW$. The receiver was a building $3 MW$×$3 MW$ containing 2 passive electronically scanned array radars as well as the command and control centre for the A-35 system. The range of the system was 2500 km.

The radar was functional until it caught fire on 8 May 1988.

Dunay-3UP
This was a prototype of the Dunay-3U and was located in Sary Shagan test site. It was given the NATO codename "Top Roost".

Dunay-3U
The Dunay-3U (Дунай-3У; NATO: Cat House) was built in 1978 as part of the upgraded A-35M anti-ballistic missile system. It is located in Chekhov and was structurally similar to the Dunay-3M – it has a separate receiver and transmitter separated by 2.7 km. There are two sectors. It was capable of identifying the launch of Pershing II missiles from West Germany.

In 1995 A-35M was replaced by the A-135 anti-ballistic missile system which used the Don-2N radar. One sector was decommissioned in 1998 and is now ruined and the other is used for space surveillance of satellites in low Earth orbit. As a UHF radar it can identify smaller objects (15–40 cm) than the VHF radars such as the Daryal and Dnepr.

The Dunay-3U was commissioned in May 1978 with a life of 12 years. Both sectors were extended until 2000 but one sector (62) was decommissioned in 1998. The other one (61) has been extended in 2001 and 2005 – the last extension was until December 2009, but it may have been extended again. In 2012 the Russian Ministry of Defence issued a tender for the demolition of sector 62.

Before 2003 the transmitter had 30 waveguides each excited by a $100 m$ transmitter. Since 2003 the station has been operating at a reduced power of $100 m$ rather than $100 kW$, with 12 transmitters (out of 24) rather than the previous maximum of 30. The radar is chirped.

The radar's computer system is made up of 10 K340 computers.