Dnestr radar Dnestr radar ( ) and Dnepr radar ( ) , both known by the NATO reporting name Hen House are the first generation of Soviet space surveillance and early warning radar s . Six of the phased array radars were built around the periphery of the Soviet Union starting in the 1960s to provide ballistic missile warnings for attacks from different directions . They were the primary Soviet early warning radars for much of the later Cold War . In common with other Soviet and Russian early warning radars they are named after rivers , the Dnestr and the Dnepr . The Dnestr / Dnepr radars were intended to be replaced by the newer Daryal radar s starting in the 1990s . Only two of the planned Daryal radars became operational , due to issues such as the dissolution of the Soviet Union . , the Russian early warning network still consists of some radars of this vintage . It is likely that all the existing radars will be replaced by the third generation Voronezh radar s by 2020 . TsSO - P . The Dnestr radar came from work on ballistic missile defence undertaken in the late 1950s and early 1960s . System A , the prototype for the A - 35 anti - ballistic missile system , was set up in the Sary Shagan testing grounds , in the Kazakh SSR . Work on the system was led by design bureau KB - 1 which proposed using VHF radar RTN ( ) and the Dunay - 2 UHF radar . Other alternatives were sought from Soviet industry and RTI proposed using VHF radar TsSO - P ( ) and UHF radar TsSS - 30 ( ) . TsSO - P ( standing for meaning " central detection station – test site " ) was selected for further development , together with the Dunay - 2 . TsSO - P had a long horn antenna long and high . It had an array with an open ribbed structure and used 200 millisecond pulses . Hardware methods were designed for signal processing as the intended M - 4 computer could not run the radar . It was built at area 8 in Sary Shagan and was located at . It first detected an object on 17 September 1961 . TsSO - P took part in the 1961 and 1962 Operation K tests at Sary Shagan to examine the effects of nuclear explosions on missile defence hardware . Dnestr . TsSO - P was effective at satellite tracking and was chosen as the radar of the Istrebitel Sputnik ( IS ) anti - satellite programme . This programme involved the construction of two sites separated in latitude to form a radar field long and high . The two sites chosen were at the village of Mishelevka near Irkutsk in Siberia , which was called OS - 1 , and at Cape Gulshad on Lake Balkhash near Sary Shagan , which was called OS - 2 . Each site received four Dnestr radar systems in a fan arrangement . A Dnestr radar was composed of two TsSO - P radar wings joined together by a two story building containing a joint computer system and command post . Each radar wing covered a 30 degree sector with a 0 . 5 degree scanning beam . The elevation scanning pattern was a ' spade ' with a width of 20 degrees . The radar systems were arranged to create a fan shaped barrier . Of the four radars , called cells ( roughly radio location cell ) , two faced to the west and two faced to the east . All scanned between + 10 degrees and + 90 degrees in elevation . Construction at the two sites started between 1962 and 1963 with improvements in the TsSO - P test model being fed back into the deployed units . They gained an M - 4 2 - M computer with semiconductor s , although the rest of the radar used Vacuum tube s . The radar systems were completed in late 1966 with the fourth Dnestr at Balkhash being used for testing . In 1968 the Dnepropetrovsk Sputnik target satellite , DS - P1 - Yu , was used to test the ability of the system . The Dnestr radars were accepted for service by the Soviet Air Defence Forces in April 1967 and became part of the space surveillance network SKKP . Dnestr - M . Parallel with the implementation of the Dnestr space surveillance units , a modified version of the original Dnestr units , Dnestr - M radar , was being developed to act as an early warning radar to identify attacks by ballistic missile s . The first two were built at Murmansk in northern Russia ( Olenegorsk – RO - 1 ) and near Riga in the then Latvian SSR ( Skrunda – RO - 2 ) . They constituted the beginning of the Soviet SPRN network , the equivalent of the NATO BMEWS . The first Dnestr - M at Olenegorsk was completed by 1968 . In 1970 , the radars at Olenegorsk and Skrunda , and an associated command centre at Solnechnogorsk , were accepted for service . According to Podvig ( 2002 ) , it seems they were positioned to identify missile launches from NATO submarines in the Norwegian and North Seas . The Dnestr - M included many improvements over the previous versions such as an increase in the pulse length from 200ms to 800ms which increased the range of objects identified , more semiconductors , and many other scanning and processing changes . A version of this radar was built at the Sary Shagan test site and was called TsSO - PM ( ) . After this had completed tests in 1965 it was decided to upgrade nodes 1 and 2 of the two OS sites to Dnestr - M , keeping nodes 3 and 4 as Dnestr . These radars remained as space surveillance radars which scanned between + 10 and + 90 degrees , comparative to scanning between + 10 and + 30 degrees for the missile warning radars . A space surveillance network of four Dnestrs and four Dnestr - Ms , and two command posts was formally commissioned in 1971 . Dnepr . Work to improve the radar continued . An improved array was designed which covered 60 degrees rather than 30 . The first Dnepr radar was built at Balkhash as a new radar , cell 5 . It entered service on 12 May 1974 . The second was a new early warning station at Sevastopol . New Dneprs were also built at Mishelevka and another at Skrunda , and then one at Mukachevo . The remaining radars were all converted to Dnepr with the exception of cells 3 and 4 at Balkhash and Mishelevka which remained space surveillance radars . All current operational radars are described as Dnepr , and have been updated incrementally . Technical details . Each Dnepr array is a double sectoral horn antenna 250m long by 12 m wide . It has two rows of slot radiators within two waveguide s . At each end of the two arrays , there is a set of transmitting and receiving equipment . It emits a signal covering a sector 30 degrees in azimuth and 30 degrees in elevation , with the scanning controlled by frequency . Four sets mean the radar covers 120 degrees in azimuth and 30 degrees in elevation ( 5 to 35 degrees ) . The Dnepr involved the horn antenna being reduced from 20 to 14 metres in height and the addition of a polarising filter Current status . These radars have been installed at six different radar stations and as of 2012 are operational at three – Balkhash , Mishelevka and Olenegorsk . The 1972 Anti - Ballistic Missile Treaty required that early warning radars were located on the periphery of national territory and faced outwards . This caused problems when the Soviet Union collapsed in 1991 as many of the radar stations were now in newly independent states . The first station to close was Skrunda , in newly independent Latvia . A 1994 agreement between Russia and Latvia agreed that the two Dnepr radars there would stop working in 1998 , and would be fully demolished by 2000 . Russia signed an agreement with Ukraine in 1992 allowing it to continue using the Dnepr radars at Sevastopol and Mukachevo . The stations were run by Ukrainian personnel and data was sent to the headquarters of the Russian early warning system in Solnechnogorsk . In 2008 Russia announced that it was pulling out of the agreement with Ukraine and that the last data given to Russia from the stations would be in 2009 . The Ukrainian government announced that the stations were to be used part - time for space surveillance . The station in Balkhash in Kazakhstan remains the only Dnepr operational outside Russia . It has been modernised and is run by the Russian Aerospace Defence Forces . The remaining stations in Russia are due to be replaced by the Voronezh radar . The Dneprs in Mishelevka , Irkutsk will close once the second array of the new Voronezh radar is operational . The Dnepr at Olenegorsk , Murmansk will be replaced by a Voronezh as well . It is planned to start construction there in 2017 .