The Dunay-3U (;
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 . 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 of the radar was decommissioned and is now abandoned while the other is used for 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 lifespan of 12 years, later being extended by ten more. Sector 62 of the radar was nonetheless decommissioned in 1998 while sector 61 had its service life extended again in 2001 and 2005 – the last extension lasting until December 2009, but it may have been extended again since. In 2012 the Russian Ministry of Defense issued a tender for the demolition of sector 62. Before 2003 the transmitter had 30
waveguides each excited by a transmitter. Since 2003 the station has been operating at a reduced power of rather than , 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. ==Locations==