| Duga radar | |
|---|---|
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| Official name | Заобрійна (загоризонтна) радіолокаційна станція "Дуга" (Over-the-horizon radar station "Duga") |
| Type | Science and Technology |
| Reference no. | 100030-Н |
Duga (Russian:Дуга,lit. 'arc' or'curve') was anover-the-horizon radar (OTH) system used in theSoviet Union as part of itsearly-warning radar network formissile defence. It operated from July 1976 to December 1989.[1] Two operational Duga radars were deployed, with one nearChernobyl andLiubech in theUkrainian SSR, and the other in easternSiberia.
The Duga system was extremely powerful, reaching over 10 MW, and emitted in theshortwave radio bands. It was given the nicknameRussian Woodpecker by shortwave listeners for its emissions randomly appearing and sounding like sharp, repetitive tapping noises at a frequency of 10 Hz.[2] The random frequency hops often disrupted legitimate broadcasts,amateur radio operations, oceanic, commercial, aviation communications, and utility transmissions, resulting in thousands of complaints from many countries worldwide. The signal became such a nuisance that some communications receivers began including "Woodpecker Blankers" in their circuit designs.[3]
The unclaimed signal was a source of speculation, giving rise to theories such as Sovietbrainwashing andweather modification experiments. However, because of its distinctive transmission pattern, many experts and amateur radio hobbyists realized it was an over-the-horizon radar system.NATO military intelligence had already given it thereporting nameSTEEL WORK orSTEEL YARD, based on the massive size of the antenna, which spanned 700 metres (2,300 ft) in length and 150 metres (490 ft) in height.[4]
The Soviets had been working onearly-warning radar for theiranti-ballistic missile systems through the 1960s, but most of these had been line-of-sight systems that were useful for rapid analysis and interception only. None of these systems had the capability to provide early warning of a launch, within seconds or minutes of a launch, which would give the defences time to study the attack and plan a response. At the time, the Sovietearly warning satellite network was not well developed. An over-the-horizon radar sited in the USSR would help solve this problem, and work on such a system for this associated role started in the late 1960s.
The first experimental system, Duga, was built outsideMykolaiv inUkraine, successfully detecting rocket launches fromBaikonur Cosmodrome at 2,500 kilometres (1,600 mi). This was followed by the prototype Duga, built on the same site, which was able to track launches from the far east and submarines in the Pacific Ocean as the missiles flew towardsNovaya Zemlya. Both of these radar systems were aimed east and were fairly low power, but with the concept proven, work began on an operational system. The new Duga-1 systems, built in 1972, used a transmitter and receiver separated by about 60 kilometres (37 mi).[5][6]
At some point in 1976, a new and powerful radio signal was detected simultaneously worldwide, and quickly dubbed 'the Woodpecker' byamateur radio operators. Transmission power on some Woodpecker transmitters was estimated to be as high as 10 MWequivalent isotropically radiated power.[7][8] Even prior to 1976, a similar woodpecker-style interference is remembered by radio amateurs occurring in thehigh frequencies. As early as 1963, or before, radio amateurs were calling this "the Russian Woodpecker".[9] Little is known about the power levels or Russian designation but it was probably a forerunner of the Duga radar systems. It was also speculated at that time, at least among radio amateurs, that this was an over-the-horizon radar.
Triangulation by amateur radio hobbyists andNATO showed the signals came from a location in present-dayUkraine, at the time called theUkrainian Soviet Socialist Republic (part of theUSSR). Confusion due to small differences in the reports being made from various sources led to the site being variously located nearKyiv,Minsk,Chernobyl,Gomel orChernihiv. All of these reports were describing the same deployment, with the transmitter only a few kilometres southwest of Chernobyl (south of Minsk, northwest of Kyiv) and the receiver about 50 kilometres (31 mi) northeast of Chernobyl (just west of Chernihiv, south of Gomel). At one time there was speculation that several transmitters were in use.[7]
The radar system was given the code 5Н32-West by the Soviets, and was set up in twoclosed towns. Liubech-1 held the two transmitters and Chernobyl-2 the receivers.[8] A second installation was built nearKomsomolsk-on-Amur, in Bolshya Kartel and Lian, but did not become active for some time.[citation needed]
The NATO reporting name for the Duga-1 is often quoted as STEEL YARD. Many online and several print references use this name. However some sources also use the term STEEL WORK (or STEEL WORKS). As any "official" sources using NATO Reporting Names are likely to be classified, establishing the true name will be difficult. The earliest found open source mention of a NATO Reporting Name for this system, a reference publication in print while the system was still active, unambiguously uses the term STEEL WORK.[10][page needed]Jane's Information Group is an often quoted open source reference for information across several military fields and subjects. Their "Jane's Radar and Electronic Warfare Systems", several editions over a number of years, uses the term "Steel Works".[11][12][13]
Even from the earliest reports it was suspected that the signals were tests of anover-the-horizon radar,[7] and this remained the most popular hypothesis during theCold War. Several other theories were floated as well, including everything from jamming western broadcasts tosubmarine communications. The broadcast jamming theory was discarded early on when a monitoring survey showed thatRadio Moscow and other pro-Soviet stations were just as badly affected by woodpecker interference as Western stations.
As more information about the signal became available, its purpose as a radar signal became increasingly obvious. In particular, its signal contained a clearly recognizable structure in eachBPSK modulatedpulse, which was eventually identified as a 31-bitpseudo-random binary sequence with properties much likeBarker codes, with abit-width of 100μs resulting in a 3.1 ms pulse.[14] The auto-correlation of this pulse/sequence results in a single 100 μs pulse 31 times the amplitude of the received sequence, giving a resolution of 15 kilometres (9.3 mi) (the distance light travels in 50 μs) and process gain of almost 30 dB. This system took advantage ofpulse compression to increase the power of the received echoes thereby increasing the sensitivity and effective range. When a second Woodpecker appeared, located in eastern Russia, but also pointed toward the US and covering blank spots in the first system's pattern, this conclusion became inescapable. These further installations allowed for more precise pin-pointing of potential targets or missiles in multiple dimensions thanks in part to the properties of theBarker codes that allow for multiple radars operating on the same frequencies without significant interference.
In 1988, the USFederal Communications Commission (FCC) conducted a study on the Woodpecker signal. Data analysis showed a pulse repetition interval (PRI) of about 90 ms, a frequency range of 7 to 19 MHz, a bandwidth of 0.02 to 0.8 MHz, and typical transmission time of 7 minutes.
The pulses transmitted by the Woodpecker had a wide bandwidth, typically 40 kHz. Theirrepetition frequencies were 10, 16 and 20 Hz with the most common frequency of 10 Hz, while the 16 and 20 Hz modes were rarely used.
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To combat this interference, amateur radio operators attempted tojam the signal by transmitting synchronized unmodulated continuous wave signals at the same pulse rate as the offending signal. They formed a club called The Russian Woodpecker Hunting Club.[15]
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Starting in the late 1980s, even as the FCC was publishing studies, the signals became less frequent, and in 1989, they disappeared. Although the reasons for the eventual shutdown of the Duga systems have not been made public, the changing strategic balance with the end of theCold War in the late 1980s may have had a part to play. Another factor perhaps was the success of theUS-KS early-warning satellites, which began entering service in the early 1980s, and by this time had grown into a complete network. The satellite system provides immediate, direct and highly secure warnings, whereas any radar-based system is subject to jamming, and the effectiveness of OTH systems is also subject to atmospheric conditions.
According to some reports, theKomsomolsk-on-Amur installation in theRussian Far East was taken off combat alert duty in November 1989, and some of its equipment was subsequently scrapped. The original Duga-1 site lies within the 30 kilometres (19 mi)Zone of Alienation around theChernobyl power plant. As of 2021,[update] the radar appears permanently deactivated and will not likely receive future maintenance because such arrangements were not included as part of the 1992 Russian and Ukrainian talks; with regards to theDnepr early warning radar systems atMukachevo andSevastopol, most of the antenna still stands and is often used by radio amateurs who visit the area using their own portable radio equipment.
The original Duga was the first experimental system.[16][17] It was built outside the Black Sea port ofMykolaiv in southernUkraine, and successfully detected rocket launches fromBaikonur Cosmodrome about 2,500 kilometres (1,600 mi) away. Duga is able to track launches from the Far East and from submarines in thePacific Ocean, as the missiles fly towardsNovaya Zemlya in the Arctic Ocean. This huge radar complex was restored in 2002 after a fire seriously damaged it. The transmitter was located at46°48′26″N32°13′12″E / 46.80722°N 32.22000°E /46.80722; 32.22000 and the receiver at47°02′28.33″N32°11′57.29″E / 47.0412028°N 32.1992472°E /47.0412028; 32.1992472. It appears[according to whom?] that the original Duga transmit and receive sites near Mykolaiv were demolished in 2006.
The original Duga was supplanted by a pair of installations: western, Duga-1, and eastern, Duga-2. Duga-1 was built in northern Ukraine, betweenLiubech andChernobyl-2. The receiver is located at51°18′19.06″N30°03′57.35″E / 51.3052944°N 30.0659306°E /51.3052944; 30.0659306, 12 kilometres west-north-west of Chernobyl; the transmitter is located at51°38′15.98″N30°42′10.41″E / 51.6377722°N 30.7028917°E /51.6377722; 30.7028917 about 50 kilometres (31 mi) northeast of Chernobyl (just west ofChernihiv, south ofGomel).
Duga-2, the eastern system, is located nearKomsomolsk-on-Amur inKhabarovsk Krai, with the receiver at50°23′07.98″N137°19′41.87″E / 50.3855500°N 137.3282972°E /50.3855500; 137.3282972, some 30 kilometres (19 mi) southeast of the city, and the transmitter at50°53′34.66″N136°50′12.38″E / 50.8929611°N 136.8367722°E /50.8929611; 136.8367722, 45 kilometres (28 mi) north of the city.
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