Dnestr radar (Russian: Днестр) and Dnepr radar (Russian: Днепр), both known by the NATO reporting name Hen House, are the first generation of Soviet space surveillance and early warning radars. Six radars of this type were built on 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 radars starting in the 1990s. Only two of the planned Daryal radars became operational, due to issues such as the dissolution of the Soviet Union. As of 2012, 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 radars by 2020.

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 (Russian: РТН) and the Dunay-2 UHF radar. Other alternatives were sought from Soviet industry and RTI proposed using VHF radar TsSO-P (Russian: ЦСО-П) and UHF radar TsSS-30 (Russian: ЦСС-30).

TsSO-P (standing for Russian: центральная станция обнаружения – полигонная meaning central detection station – test site) was selected for further development, together with the Dunay-2. TsSO-P had a long horn antenna 250 metres (820 ft) long and 15 metres (49 ft) high. It had an array with an open ribbed structure and used 200 microseconds pulses. Hardware methods were designed for signal processing as the intended M-4 computer could not run the necessary computations. It was built at area 8 in Sary Shagan and was located at 46°00′04.65″N 73°38′52.11″E / 46.0012917°N 73.6478083°E / 46.0012917; 73.6478083. It first detected an object on 17 September 1961.

TsSO-P took part in the 1961 and 1962 Soviet Project K nuclear tests above the Sary Shagan range to examine the effects of high altitude nuclear explosions on missile defence hardware.

Dnestr is a Phased array, Azimuth scanning by frequency modulation with no elevation scanning.

TsSO-P was effective at satellite tracking and was chosen as the radar of the Istrebitel Sputnikov (IS) anti-satellite programme. This programme involved the construction of two sites separated in latitude to form a radar field 5,000 kilometres (3,100 mi) long and 3,000 kilometres (1,900 mi) 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 (Russian: РЛЯ, romanized: RLYa 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.