Duga (Russian: Дуга, meaning "arc" or "curve") was a type of over-the-horizon radar (OTH) system used by the Soviet Union in its early-warning radar network for missile defense. It operated from July 1976 to December 1989. Two Duga radars were built: one near Chernobyl and Liubech in Ukraine, and the other in eastern Siberia.
The Duga system was very powerful, using up to 10 megawatts of energy, and sent signals in the shortwave radio bands. It became known as the "Russian Woodpecker" by shortwave radio listeners because its signals sounded like sharp, repetitive tapping noises at a frequency of 10 Hz. These signals often disrupted radio broadcasts, amateur radio communications, and transmissions used for oceanic, commercial, and aviation purposes. This caused complaints from many countries around the world. To reduce the interference, some radio receivers were designed with special filters called "Woodpecker Blankers."
The mysterious signal led to many theories, such as experiments related to brainwashing or weather control. However, experts and radio hobbyists recognized the signal as an over-the-horizon radar system because of its unique transmission pattern. NATO military intelligence had already given it the code names "STEEL WORK" or "STEEL YARD," referring to the radar's massive antenna, which was 700 meters (2,300 feet) long and 150 meters (490 feet) tall.
History
The Soviet Union worked on early-warning radar systems for their anti-ballistic missile defenses during the 1960s. Most of these systems were line-of-sight, meaning they could only detect objects that were visible directly. These systems were useful for quickly analyzing and intercepting threats, but they could not warn of missile launches seconds or minutes before they happened. This would have given defenses time to study attacks and prepare responses. At the time, the Soviet Union’s early warning satellite network was not well developed. An over-the-horizon radar located in the USSR could help solve this problem, and work on such a system began in the late 1960s.
The first experimental system, called Duga, was built outside Mykolaiv in Ukraine. It successfully detected rocket launches from Baikonur Cosmodrome, 2,500 kilometers (1,600 miles) away. A later prototype, also called Duga, was built on the same site. This version could track launches from the far east and submarines in the Pacific Ocean as missiles traveled toward Novaya Zemlya. Both systems were aimed east and used low power, but after proving the concept, the Soviets began building an operational system. The new Duga-1 systems, built in 1972, used a transmitter and receiver separated by about 60 kilometers (37 miles).
In 1976, a powerful radio signal was detected worldwide and called “the Woodpecker” by amateur radio operators. Some Woodpecker transmitters had power as high as 10 megawatts. Similar interference was reported earlier, and radio amateurs had already called it “the Russian Woodpecker” as early as 1963. Little is known about its power levels or Soviet designation, but it was likely an early version of the Duga radar systems. At the time, radio amateurs speculated it might be an over-the-horizon radar.
Amateur radio hobbyists and NATO used triangulation to locate the signal’s source in present-day Ukraine, then called the Ukrainian Soviet Socialist Republic. Reports from different sources led to confusion about the exact location, with some claiming it was near Kyiv, Minsk, Chernobyl, Gomel, or Chernihiv. All these reports described the same deployment, with the transmitter a few kilometers southwest of Chernobyl and the receiver about 50 kilometers (31 miles) northeast of Chernobyl. Some speculated multiple transmitters were used.
The Soviet Union gave the radar system the code 5Н32-West and set it up in two closed towns: Liubech-1, which held the transmitters, and Chernobyl-2, which held the receivers.
The NATO reporting name for Duga-1 is often called “STEEL YARD,” though some sources use “STEEL WORK” or “STEEL WORKS.” The earliest open-source reference to a NATO name, from a publication while the system was active, used “STEEL WORK.” Jane’s Information Group, a well-known source for military information, also used “Steel Works” in its publications.
From the earliest reports, it was suspected the signal was from an over-the-horizon radar. This remained the most popular theory during the Cold War. Other theories, such as jamming Western broadcasts or submarine communications, were later dismissed. For example, the broadcast jamming theory was ruled out when it was found that both pro-Soviet and Western stations were equally affected by the interference.
As more information about the signal became available, its purpose as a radar signal became clearer. The signal had a specific structure in each pulse, identified as a 31-bit pseudo-random binary sequence with properties similar to Barker codes. This allowed the system to detect objects with high accuracy. The signal’s properties also enabled multiple radars to operate on the same frequencies without significant interference. A second Woodpecker signal, located in eastern Russia and also aimed at the United States, confirmed the system’s purpose.
In 1988, the U.S. Federal Communications Commission (FCC) studied the Woodpecker signal. The analysis found a pulse repetition interval of about 90 milliseconds, a frequency range of 7 to 19 MHz, a bandwidth of 0.02 to 0.8 MHz, and typical transmission times of 7 minutes. The pulses had a wide bandwidth of 40 kHz and repetition frequencies of 10, 16, and 20 Hz, with 10 Hz being the most common.
To combat the interference, amateur radio operators tried to jam the signal by sending synchronized signals at the same pulse rate. They formed a group called The Russian Woodpecker Hunting Club.
Starting in the late 1980s, the Woodpecker signals became less frequent and disappeared completely in 1989. The reasons for the shutdown of the Duga systems are not publicly known, but the end of the Cold War in the late 1980s may have played a role. Another factor could have been the success of U.S. early-warning satellites, which began operating in the early 1980s and formed a complete network. These satellites provided immediate, secure warnings, unlike radar systems, which are vulnerable to jamming and atmospheric conditions.
Locations
The original Duga was the first experimental system. It was built outside the Black Sea port of Mykolaiv in southern Ukraine. It successfully detected rocket launches from Baikonur Cosmodrome, about 2,500 kilometers (1,600 miles) away. Duga could track launches from the Far East and from submarines in the Pacific Ocean as the missiles traveled toward Novaya Zemlya in the Arctic Ocean. This large radar system was restored in 2002 after a fire caused serious damage. The transmitter was located at 46°48′26″N 32°13′12″E / 46.80722°N 32.22000°E / 46.80722; 32.22000, and the receiver was at 47°02′28.33″N 32°11′57.29″E / 47.0412028°N 32.1992472°E / 47.0412028; 32.1992472.
The original Duga was replaced by two installations: the western Duga-1 and the eastern Duga-2. Duga-1 was built in northern Ukraine, between Liubech and Chernobyl-2. The receiver is located at 51°18′19.06″N 30°03′57.35″E / 51.3052944°N 30.0659306°E / 51.3052944; 30.0659306, 12 kilometers west-northwest of Chernobyl. The transmitter is located at 51°38′15.98″N 30°42′10.41″E / 51.6377722°N 30.7028917°E / 51.6377722; 30.7028917, about 50 kilometers (31 miles) northeast of Chernobyl (just west of Chernihiv, south of Gomel).
Duga-2, the eastern system, is located near Komsomolsk-on-Amur in Khabarovsk Krai. The receiver is at 50°23′07.98″N 137°19′41.87″E / 50.3855500°N 137.3282972°E / 50.3855500; 137.3282972, about 30 kilometers (19 miles) southeast of the city. The transmitter is at 50°53′34.66″N 136°50′12.38″E / 50.8929611°N 136.8367722°E / 50.8929611; 136.8367722, 45 kilometers (28 miles) north of the city.
Media appearances
The Ukrainian-developed computer game series S.T.A.L.K.E.R. is based on the Chernobyl Nuclear Power Plant and the nuclear accident there. The game includes real locations from the area, such as the Duga-1 array. This array appears in the game S.T.A.L.K.E.R.: Clear Sky in the fictional city of Limansk-13. 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, but it does not look like the real array. However, in the 2024 game S.T.A.L.K.E.R. 2: Heart of Chornobyl, the Duga-1 site is a place players can explore. In the game's story, the "Monolith" faction tries to use Duga-1 in the same way as the "Brain Scorcher" in S.T.A.L.K.E.R.: Shadow of Chernobyl.
In Call of Duty: Black Ops, the map "Grid" is set near the Duga-1 array in Pripyat. A later game in the series, Call of Duty: Cold War, uses the Duga as a location for a final mission and as a map in the Zombies game mode called "Outbreak." This map is named "Duga" and includes rappel lines that allow players to climb to the top or middle of the structure, even though the real radar array does not have these features.
The Duga antenna array is also shown in the revised map "Verdansk '84" in the game Call of Duty: Warzone. The Duga radar appears in the drone racing simulator Liftoff as "The Russian Woodpecker." A Duga radar is included in the 2017 game PUBG: Battlegrounds in a map that shows a fictional Russian military base. The Chernobyl DLC for the game Spintires includes a representation of the sarcophagus and an antenna array that looks similar to Duga.
The Duga radar is a major part of the virtual reality game Proze: Enlightenment, a suspense/puzzle game that suggests the radar was used for mind control experiments during the 1950s and 1960s. The game begins with the player climbing one of the radar's pylons using a maintenance lift. A Duga radar is also featured in the 2021 video game Chernobylite.
Markiyan Kamysh's book Stalking the Atomic City: Life Among the Decadent and the Depraved of Chornobyl describes illegal trips to the Chernobyl Exclusion Zone, including visits to the Duga. The book was praised by reviewers and listed as one of the "Constellations of the ten books that best reflect the spirit of the times" by La Repubblica in 2019. The Guardian called it a "remarkable book."
The Duga at Chernobyl was the subject of the 2015 documentary film The Russian Woodpecker, directed by Chad Gracia. The film includes interviews with the commander of the Duga, Vladimir Musiets, the Vice-Commander, and the Head of the Data Center, among others. It also shows drone and handheld video footage of the area and includes a climb to the top of the radar by the cinematographer, Artem Ryzhykov. The film suggests a conspiracy theory that the Chernobyl disaster was created to hide problems with the radar's design.
The Chernobyl Duga site is featured in the Science Channel series Mysteries of the Abandoned (Season 1, Episode 1).