Duga (Russian: Дуга́, literally "arc" or "curve") was a Soviet over-the-horizon radar (OTH) system used as part of the missile defense early-warning radar network. The system operated from July 1976 to December 1989. Two operational duga radars were deployed, one near Chernobyl and Chernihiv in the Ukrainian SSR (present-day Ukraine), the other in eastern Siberia.
The duga systems were extremely powerful, reaching over 10 MW, and broadcast in the shortwave radio bands. They were nicknamed Russian Woodpecker by shortwave listeners for their emissions randomly appearing and sounding like a sharp, repetitive tapping noise at 10 Hz rate. The random frequency hops disrupted legitimate broadcasts, amateur radio operations, oceanic commercial aviation communications, and utility transmissions, resulting in thousands of complaints by many countries worldwide. The signal became such a nuisance that some receivers used on amateur radio and television, began including "Woodpecker Blankers" in their circuit designs.
The unclaimed signal was a source for much speculation, giving rise to theories such as Soviet mind control and weather control experiments. However, because of its distinctive transmission pattern, many experts and amateur radio hobbyists quickly realized it to be an over-the-horizon radar system. NATO military intelligence had already given it the reporting name STEEL WORK or STEEL YARD likely based on the massive size of the antenna which spanned 700 metres (2,300 ft) in length and 150 metres (490 ft) in height. While the amateur radio community was well aware of the system, this theory was not publicly confirmed until after the dissolution of the Soviet Union.
The Soviets had been working on early warning radar for their anti-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 Soviet early-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 outside Mykolaiv in Ukraine, successfully detecting rocket launches from Baikonur 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 towards Novaya 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).
At some point in 1976, a new and powerful radio signal was detected simultaneously worldwide, and quickly dubbed 'the Woodpecker' by amateur radio operators. Transmission power on some Woodpecker transmitters was estimated to be as high as 10 MW equivalent isotropically radiated power. Even prior to 1976, a similar 'woodpecker' interference is remembered by radio amateurs occurring in the high frequencies. As early as 1963, or before, radio amateurs were calling this "the Russian Woodpecker". 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.
These signals even caused interference on 27 MHz CB radios in the late 60's and early 70's sometimes completely blocking even local communications in Portugal for example, leading to the supposition of several Megawatts of RF power transmission.
Triangulation by both amateur radio hobbyists and NATO quickly revealed the signals came from a location in present-day Ukraine, at the time called Ukrainian Soviet Socialist Republic (part of USSR). Confusion due to small differences in the reports being made from various sources led to the site being variously located near Kiev, Minsk, Chernobyl, Gomel or Chernihiv. All of these reports were describing the same deployment, with the transmitter only a few kilometers southwest of Chernobyl (south of Minsk, northwest of Kyiv) and the receiver about 50 km (30 miles) northeast of Chernobyl (just west of Chernihiv, south of Gomel). At one time there was speculation that several transmitters were in use.
The radar system was given the code 5Н32-West by the Soviets, and was set up in two closed towns, Liubech-1 held the two transmitters and Chernobyl-2 the receivers. Unknown to civilian observers at the time, NATO was aware of the new installation. A second installation was built near Komsomolsk-on-Amur, in Bolshya Kartel and Lian, but did not become active for some time.
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.[page needed]
Even from the earliest reports it was suspected that the signals were tests of an over-the-horizon radar, and this remained the most popular hypothesis during the Cold War. Several other theories were floated as well, including everything from jamming western broadcasts to submarine communications. The broadcast jamming theory was discarded early on when a monitoring survey showed that Radio 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 each pulse, which was eventually identified as a 31-bit pseudo-random binary sequence, with a bit-width of 100 μs resulting in a 3.1 ms pulse. This sequence is usable for a 100 μs chirped pulse amplification system, giving a resolution of 15 km (10 mi) (the distance light travels in 50 μs). When a second Woodpecker appeared, this one located in eastern Russia but also pointed toward the US and covering blank spots in the first system's pattern, this conclusion became inescapable.
In 1988, the U.S. Federal 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.
To combat this interference, amateur radio operators attempted to jam 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. Core group members would frame the "Official Practice Target" in their radio shacks.
Starting in the late 1980s, even as the FCC was publishing studies, the signals became less frequent, and in 1989, they disappeared altogether. Although the reasons for the eventual shutdown of the Duga systems have not been made public, the changing strategic balance with the end of the Cold War in the late 1980s likely had a major part to play.[according to whom?] Another factor was the success of the US-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, the Komsomolsk-on-Amur installation in the Russian 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 the Chernobyl power plant. As of today, the radar appears permanently deactivated and will not likely receive future maintenance because such arrangements were not implemented within Russian and Ukrainian talks; with regards to the Dnepr early warning radar systems at Mukachevo and Sevastopol. Most of the antenna still stands to this day 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. It was built outside the Black Sea port of Mykolaiv in the southern Ukraine, and successfully detected rocket launches from Baikonur Cosmodrome about 2,500 kilometers (1500 miles) away. Duga is able to track launches from the Far East and from submarines in the Pacific Ocean, as the missiles fly towards Novaya Zemlya in the Arctic Ocean. This huge radar complex was restored in 2002 after a fire seriously damaged it. The transmitter was located at and the receiver at . It appears that the original Duga transmit and receive sites near Mykolaiv, Ukraine 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, between Liubech and Chernobyl-2. The receiver is located at a few kilometers (miles) west-north-west of Chernobyl; the transmitter is located at about 50 kilometres (31 mi) northeast of Chernobyl (just west of Chernihiv, south of Gomel). The site is open for pre-arranged visits, for which a permit must be obtained in advance; it has been open since approximately 28 October 2013. Operators who provide tours of Chernobyl and the surrounding areas are able to obtain the relevant paperwork.
Duga-2, the eastern system, is located near Komsomolsk-on-Amur in Khabarovsk Krai, with the receiver at , some 30 kilometres (19 mi) southeast of the city, and the transmitter at , 45 kilometres (28 mi) north of the city.
The Ukrainian-developed computer game S.T.A.L.K.E.R. has a plot focused on the Chernobyl Nuclear Power Plant and the nuclear accident there. The game features many actual locations in the area, including the duga-1 array. The array itself appears in S.T.A.L.K.E.R.: Clear Sky in the fictional city of Limansk-13. While the 'Brain Scorcher' from S.T.A.L.K.E.R.: Shadow of Chernobyl was inspired by theories that duga-1 was used for mind control, it does not take the form of the real array.
Markiyan Kamysh's novel about illegal trips to the duga, A Stroll to the Zone, was praised by reviewers as the most interesting literature debut of 2015 in Ukraine. The novel has been translated into French (with the title La Zone), and was published by French publishing house Arthaud (Groupe Flammarion).
In Call of Duty: Black Ops, the map "Grid" is placed in Pripyat near the duga-1 array. A game later in the series, Cold War, uses the duga as location for a possible final mission and as a map in the Zombies game-mode “Outbreak”, the map being appropriately named "Duga". Said map has rappel lines that can take the player(s) up to the top or middle of the duga, despite the actual radar array lacking this.
The duga antenna array is also featured on the revised map "Verdansk '84" in the game Call of Duty: Warzone.
The 'Russian woodpecker' appears in Justin Scott's novel The Shipkiller.
The duga at Chernobyl was the focus of the 2015 documentary film, The Russian Woodpecker, by Chad Gracia. The film includes interviews with the commander of the duga, Vladimir Musiets, as well as the Vice-Commander, the Head of the Data Center, and others involved in building and operating the radar. The documentary, which won numerous awards, also includes drone video footage of the array and handheld video footage of the surroundings as well as a climb to the top by the cinematographer, Artem Ryzhykov. The film also proposes a conspiracy theory that the Chernobyl disaster was engineered to cover up failures in the radar's design.
The duga radar is also featured in the films of the Divergent series, where it was used as the giant wall and fence surrounding the main city. In wide shots, its structure was used to create computer-generated imagery of the superstructure and several close-up scenes were shot directly at its location.
A duga radar is featured in the 2017 game Player Unknown's Battlegrounds in a map which portrays a fictional Russian Military base.
The duga radar is heavily featured in the virtual reality game Proze: Enlightenment, a suspense/puzzle game with the theory that the radar is being used by mind controlling experiments during the 1950-60s. The game actually starts with the player ascending one of the pylons on a maintenance lift.
A duga radar is featured in the 2019 video game Chernobylite.
In episode 12 of the first season of the NBC science fiction series Debris, the Duga radar array makes an appearance as a fictional array in the state of Virginia.
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