Mysterious Cold War Signals

ASA SIGINT truck at Czech border
Source: ASA Det J Schneeberg Vets

An important part of the Cold War was fought over radio waves and all sorts of radio signals filled the aether. A shortwave or VHF receiver with a good antenna was, and still is, all you need to discover innumerable signals. Of course, these signals also caught the attention of both radio amateurs and intelligence organisations.

 

Signals intelligence (SIGINT) comprises communications intelligence (COMINT) and electronic intelligence (ELINT). The latter is the interception and analysis of various technical signals such as weapons systems, navigation and radar. ELINT was an important part of the Cold War and is today still an indispensable part of modern intelligence gathering and warfare.

The secrets behind the signals were often revealed, either by ELINT or HUMINT (Human Intelligence i.e. espionage). However, some signals remained unidentified for decades and even rose to the stardom of mysterious Cold War signals. Speculation about their purpose fueled the paranoia of that era. Occupying certain frequencies for use in case of war, or the notorious Dead Hand autonomous launch system for nuclear missiles that would initiate a launch when the mysterious signal interrupted. Eerie, but only speculations.

Tracking Nukes

One of those mysterious signals was nicknamed Russian Woodpecker, with its characteristic repetitive tapping noise. The Woodpecker's annoying high-power signal - an estimated 10 Megawatt - switched between different frequencies and disrupted legitimate HF signals (3-30 MHz) from utility and amateur communications across the world. The signal first appeared in 1976 and continued until 1986. Only after the fall of the Soviet Union it was confirmed that the signal came from an over-the-horizon (OTH) radar, part of Soviet early warning system for  ICBMs (intercontinental ballistic missiles, i.e.nukes).

Receiver antennas Chernobyl-2 site from the Duga-1 (source: Ingmar Runge)

The Soviet Duga-1 OTH (Rus. Дуга-1 ЗГРЛС) comprised two military sites in the Ukrainian Soviet Socialist Republic (SSR). The Liubech-1 transmitter site near Kloniv, and 50 km southwest the Chernobyl-2 receiver site near Chernobyl. Both transmitter site and receiver site each had two giant antennas. The huge antenna for the lower HF frequencies (right on photo) was 450 m (1476 ft) wide and 150 m (492 ft) high. The "small" antenna for the higher HF frequencies (left) was 250 m (820 ft) wide and 90 m (295 ft) high.

Duga-1 became operational in 1976 and was directed over Greenland towards North America. The Chernobyl-2 site was codenamed STEEL YARD by Western military intelligence, who apparently managed to photograph the site during the Cold War.

Coverage Duga-1, 2 and N radars
(Earth's northerly top view)

The first experimental OTH radar, called Duga-N or Duga (no number) was located in Ukraine near Mykolaiv at the Black Sea and directed towards China. Duga-N became operational in 1972.

The Duga-2 radar was located in the far east of the USSR, in the region Komsomolsk-on-Amur, with the transmitter in Lian and receiver in Bol'shaya Kartel, 50 km southeast of Lian. Duga-2 was directed over the North Pole towards Canada and North America. Note that the map shows the approximate coverage of the radars, not necessarily the actual reach, which depended on various conditions.

The Duga was designed to track ICBMs at 6-10.000 km (3400-6200 mi) and aircraft up to 3000 km (1865 mi). The actual range depended on the ionospheric conditions. They operated between 5 and 28 MHz, right on HF band (3-30 MHz), causing the strong interference. The huge antennas were phased array antennas where the beam could be directed electronically without any moving parts. The received signals were processed digitally.

 

Peeking Beyond the Horizon 

 

Most radar waves (30 MHz up to 300 GHz) go straight ahead. Radar therefore works line-of-sight (LOS) and the curvature of the Earth limits its range. You can't look beyond the horizon, only above it. If the Duga with its 150 m (492 ft) high antenna was a normal LOS radar, it's horizon was a mere 44 Km (27 mi) away, since the distance to its horizon in kilometer = √ 13 x 150 m (for miles use 1.5 x ft).

Therefore, the further an ICBM or nuclear bomber is, the higher it must fly or the closer it must get to become visible above the radar's horizon, and that's way too long after its launch. LOS radar was therefore insufficient to provide early warning in case of an attack against the Soviet Union.

The solution to this problem was the over-the-horizon radar station. In Russian, Загоризо́нтная радиолокационная станция (ЗГРЛС) i.e. Zagorizóntnaya radiolokatsionnaya stantsiya (ZGRLS).

Over-the-horizon radar principle

Over-the-horizon (OTH) radar transmits a powerful HF signal towards the ionosphere. Depending on the angle of the signal, the ionosphere reflects the signal back to Earth over a long distance, a so-called skip (hence the name Duga, Russian for arc) and can also reflect the signal from Earth back to the ionosphere multiple skips in a zigzag pattern, traveling huge distances around Earth.

When the OTH signal hits a moving ICBM, the reflected signal creates a small frequency shift (Doppler effect) as any radar does. However, only a very small portion, called backscatter, is reflected back by the ionosphere and effectively received by the OTH station. Complex digital processing is required to extract and analyse the very weak signal and the effect of the ionosphere and skips on the backscatter. Its accuracy and resolution are low, but the system works good enough for a raw early warning.

Disaster and Downfall of Duga- 1 

 

Noteworthy is that the Duga-1 receiver site Chernobyl-2 is located only 10 km (6 mi) from the Chernobyl nuclear power plant. According to Vladimir Musiyets, former Commander Chernobyl-2, the installation was damaged during the 1986 Chernobyl disaster and never became operational again. The site now lays within the 30 km (18 mi) Chernobyl exclusion zone. Some sources state that the Woodpecker continued broadcasting until 1989. These reportings possibly refer to other OTH sites.

On the history of over-the-horizon radar (translation) by Yuri Davydov, chief designer OTH radar, details the history and technical aspects of the Duga radars. The Ukrainian Chernobyl -2: the secret twin of the city Chernobyl (translation) from the exclusion zone website has a short history and photos. Global Security also has details on the Duga stations. Radartutorial explains phased array antennas for radar, but if you're not that technical, watch Duga Radar - How it Works.

 

Chernobyl 35 Years Later has excellent photos of the Duga-1 antenna, the control station and its consoles. To get a good sense of the sheer size of the Duga-1 antennas, visit English Russia and check the 14th photo with people underneath the antenna. Many more photos at Lost Places and Egorka's gallery.

Note: The following video mistakenly states "Duga-3 alias Chernobyl 2". The Chernobyl-2 receiver in this video was, together with the Liubech-1 transmitter, part of Duga-1. There was never a Duga-3.

Chernobyl: The Duga radar (Russian Woodpecker)

 

Note: The BBC video mistakenly translated site "Chernobyl-2" into system "Duga-2", although Sergei Babakov in the interview correctly said "Чернобыль-2", which is part of Duga-1. Duga-2 was in the Far East, 9000 Km from Chernobyl. The video title should be Duga-1.

 

The secret Soviet radar hidden in Chernobyl’s shadow - BBC REEL

The mistakes about the different Duga radars are understandable, as each Duga had two separate sites, one transmitter and one receiver site, and the site numbers didn't match the unrelated Duga number.

 
Substitutes for the Duga System

By the mid-1980s it became clear that the computer technology, used for the Duga phased array radars, was insufficient. However, the 1972 Око program for early warning satellites resulted in the first-generation US-K and US-KS satellites, operational in 1982 and the Око-1 program with second generation УС-КMO satellites in 1991. From 2015 on, these satellites were replaced by satellites of the Unified Space Detection System and Combat Control system.

 

In 2005 the Russian Federation also started to build a new generation of phased array radars for early warning, called Voronezh. Seven of these radars are already operational across Russia. More detailed info at Russia's Modern Early Warning Systems.

Buzzing Air and Messages for Spies

Another famous mysterious Soviet signal is known under its call-sign UVB-76. The station, nicknamed The Buzzer, started in 1982 with a two-seconds beep tone and switched after a decade of operation to a monotonous 25 buzz tones per minute, every single day. The station was extensively observed by radio amateurs (without doubt an equally monotonous job) and only a handful of voice conversations were recorded in its 28 years of operation.

Its call-sign UVB-76 was revealed during one of its rare voice conversations. The purpose of The Buzzer remains unknown until today. UVB-76 stopped broadcasting in August 2010 and remains silent since then. The transmitter site is located near Povarovo, 40 km (25 mi) north-west of Moscow, and now appears abandoned.

The UVB-76 "Buzzer" at Numbers Stations Research and Information Center, including some rare voice recordings. Photos of the abandoned alleged Buzzer site are published on English Russia.

Another true Cold War icon are the notorious Numbers stations. The stations broadcast streams of numbers or letters in voice or Morse and are used by intelligence agencies to communicate with their agents, operating abroad. Although the Cold War officially ended, there are still many active numbers stations and new keep popping up.

 

Further Information about SIGINT on the Blog

• Tracking Cold War Signals Wullenweber FLR-9 antenna
• 3 Second from World War 3 Early warning going wrong 
• Russia's Modern Early Warning Systems
  
• OXCART and ELINT Research Stealth for A-12 and SR-71
• Silent Warriors, USAF C-130 downing in Soviet airspace
• USS Pueblo Incident Capture SIGINT ship by North Korea
• Numbers Stations and many related spy cases on the blog
  
• More posts about signals intelligence
  
  

More About SIGINT on the Website

Cold War Signals details the SIGINT battle during the Cold War. You can listen to many audio samples of signals from spy transmitter and international shortwave broadcast stations.

Numbers Stations explains the origins of these broadcasts, their purpose, who uses them and their encrypted messages. Also many documents of the spies cases that involved numbers stations.

Russia’s Modern Early Warning Systems

Duga-1 OTH Receiver
Source: Ingmar Runge

During the Cold War, the Soviet Union developed various early warning systems to detect the launch of  intercontinental ballistic missiles (ICBMs).

The Duga OTH (over-the-horizon) radar was a well known example. Although top secret at the time, the Duga soon got nicknamed "the woodpecker" in the West because of its characteristic repetitive tapping noise that disrupted HF utility and communications signals across the world. By the mid-1980s it became clear that the Duga's technology at the time was inadequate. More about the Duga radar in our Mysterious Cold War Signals.

With the Duga radars no longer operational, what other systems protected the Soviet Union and now Russia? The SPRN System Warning on Missile Attack (Rus. Sistema Preduprezhdeniya o Raketnom Napadenii) consist of both satellites and land-based radar.

Early Soviet Satellite Program
 

The Soviet Око program (Eng. eye) to develop early warning satellites was already initiated in the late 1960s. Its first US-K satellite Космос-520 (Eng. Cosmos) was launched in 1972. To this day, all early warning satellites are designated Космос, followed by a three or four-digit number.

This first generation US-K Managed Satellite Continental (Rus. Upravlyayemyy Sputnik Kontinental'nyy) was placed in a highly elliptical Molniya orbit.  The similar US-KS Managed Satellite Continental Stationary (Rus. Upravlyayemyy Sputnik Kontinental'nyy Statsionarnyy) was placed in geosynchronous orbit. More on orbits in the further reading links.

US-K and US-KS Satellite

The first 13 US-K satellites, launched between 1972 and 1979, were very unreliable and short-lived. The following US-K and US-KS satellites were launched from 1979, with the first combat ready in 1982. In total, 86 US-K and 7 US-KS satellites were launched between 1972 and 2010. The large number of satellites was due to their limited lifespan, on average 2 to 4 years, largely determined by their liquid-fuel reserve for the orbit correction engines.

They carried a stabilized infrared telescope with 50 cm mirror to detect missile exhaust heat, and were also equipped with multiple smaller telescopes. They didn't always work flawlessly, with dangerous consequences, as you can read in our 3 Seconds from World War 3.

Second Generation Око-1 with Issues

The second generation satellites from the Око-1 program launched between 1991 and 2012 eight US-KMO Managed Satellite Control Ocean Seas (Rus. Upravlyayemyy Sputnik Kontrol' Morey Okeanov) in a geosynchronous orbit, with an expected lifespan of 5 to 7 years, which they never lived up to.

US-KMO Satellite
Source: Novosti Kosmonavtik

The US-KMO had a 100 cm mirror and could also detect submarine-launched ballistic missiles (SLBMs). However, they proved very unreliable to detect such missile launches and several failed after a few months.  They are no longer operational since 2014. Only two older US-KS satellites remained in orbit.

 

The Unified Space System

From 2015 on, the US-КMO satellites were gradually replaced by the new generation Tundra satellites (Тундра), part of the EKS Unified Space System - Detection and Combat Control (Rus. Edinoy Kosmicheskoy Sistemy - Obnaruzheniya i Boyevogo Upravleniya), also known as Kupol (Купол).

 

A this moment, five Tundra satellites are in a Molniya orbit, despite the satellite's name suggesting the highly elliptical geosynchronous Tundra orbit (taking a full sidereal day) which has a closed figure 8 ground track with a small fast loop and a large slow loop (apogee dwell). Tundra's large slow loop provides very long coverage of the designated area, requiring only two satellites for continuous cover, versus three with Molniya orbit (half a sidereal day). The Molniya orbit might be chosen because it requires less launch energy than a Tundra orbit (a sidereal day is one Earth rotation of 23h 56m 04s).

At Gunter's Space Page more details on the US-K, UK-KS, US-KMO and Tundra satellites. The US-K was carried in orbit with the Molniya-M launcher, both US-KS and US-KMO with the Proton-K launcher, and the Tundra with Soyuz-2-1b Fregat. The contractor for most of the satellites is Kometa Corporation (translation), previously known as TsNII Kometa. The Tundra is manufactured by RKK Energia.

Today's Early Warning Radar

The Russian Federation also revived the long-distance early warning capabilities to track ballistic missiles with a new generation of radar, called 77Ya6 Voronezh (Rus. 77Я6 Воронеж). The NIIDAR scientific research institute initiated its research for early warning radar in the late 1970s.

The Voronezh  is a line-of-sight phased array radar, a fixed antenna that directs its radar beam electronically. There are five different types. The Voronezh-M (VHF), DM (UHF), VP (high-power VHF), SM (SHF) and MSM (dual VHF-SHF). They have a range up to 6000 km (3728 mi) and can track 500 targets simultaneously. The first Voronezh on actual combat duty operates since 2009. Meanwhile, seven of ten planned radars are operational across Russia.

Voronezh-M Radar in Lekhtusi, Leningrad region (source Russian Army)

The Voronezh is  the first radar of VZG High Factory Readiness (Rus. Vysokoy Zavodskoy Gotovnosti). Its factory-made modular structures allow fast construction, between one and two years. More technical information and many detailed images of the Voronezh radar at Military Russia blog (translation) and at New Defense Order (translation).

One Voronezh-DM radar is located near Pionersky, a city in the Kaliningrad oblast. This is a quite unique but smartly chosen location, as Kaliningrad is today completely surrounded by Poland and Lithuania, two EU countries that are also NATO members.

Kaliningrad was previously the East Prussian city Königsberg, part of Germany. After the Second World War, Kaliningrad became part of the Soviet Union and the Kaliningrad oblast became an administrative part of the Russian Federation in 1991. This required special travel arrangements for the inhabitants, enclosed between Poland and Lithuania. An early warning system for nuclear missiles inside the territory of the main adversary? That's as close as it gets!

 

 
50 лет назад создана система предупреждения о ракетном нападении (archived)
Missile attack warning system created 50 years ago
(auto-translate available)

на новой суперсовременной РЛС семейства Воронеж
State-of-the-art radar of Voronezh family (auto-translate available)

Further Reading and Technical Details

Satellites and Orbits

• Око program (translation) at Command and Measurement Complex.
• Tundra satellite at Space Review history and tech details sensors Tundra and predecessors US-K and US-KMO.
• Tundra Satellites (translation) at Defense New Order Strategy. 
• Russia’s Soyuz-2-1b launche of 4th Tundra at NASA Spaceflight.com
• Orbit types video from NSSI explains the geostationary orbit and the highly elliptical Molniya orbit with the equator's perturbation acceleration effect.
• Catalog of Earth Satellite Orbits at NASA's Earth Observatory.
• Siderial Day Neil deGrasse Tyson explains the duration of Earth's rotation.
  

Early Warning Systems

• Ground and space echelons of SPRN with various radars and satellites at Top War.
  
• Forewarned Means Protected (translation) 50 years OTH radar and Missile Warning System, from the Armed Forces Red Star newspaper.
  
• Russia's NC3 and Early Warning Systems L. Ryabikhin.
• ESKOiBU system (translation)  Unified Space Detection and Combat Control System, Defense New Order Strategy. 

         Satellite Manufacturers

• History of Kometa Corporation (translation) including links to their first generation and second generation satellites. See also as history of TsNII Kometa.
• RKK Energia Rocket and Space Corporation and its rocket and space history.

More Related on This Blog

• Mysterious Cold War Signals with a detailed description of the Duga phased array over-the-horizon radar.
• 3 Seconds from World War 3 The story of a Soviet satellite that mistakenly triggered a missile warning.
• Dead Hand Revealed How the Soviets could still execute a retaliatory nuclear strike, even if a U.S. strike was detected too late.
• US Strategic Intelligence on the USSR and miscalculation of Soviet aggressiveness during the Cold War.

3 Seconds from World War 3

Stanislav Petrov

September 1, 1983. Soviet airspace over the Sakhalin Island. A Korean Boeing 747, flying from the US to South Korea, doesn't respond after violating Soviet airspace a second time. After escorting the 747 for more than an hour, two Soviet SU-15 interceptor aircraft receive the order to shoot down the airplane. 269 passengers and crew are killed.

The Cold War is on its hottest ever. The US military superiority feeds the belief of the Kremlin that a First Strike scenario by the United States is only a question of 'when'. What happens 4 weeks later should be viewed in that context.

On the night of September 26, lieutenant colonel Stanislav Petrov resumed his shift in a bunker of the Strategic Rocket Forces. The unimaginable happens when a Soviet УС-К Satellite from the Missile Early Warning System detects the launch of a U.S. ICBM and the computers report the incoming missile. According to Soviet strategy protocol, an immediate full-blown nuclear weapons counterattack against the US should be launched.

Colonel Petrov cannot believe that World War 3 has begun. Why only one missile? He's convinced it's a computer error and decides not  to confirm the missile launch to higher command, which might start a nuclear counterstrike. However, only minutes later, a second, a third and a fourth missile are detected. The USSR is under missile attack! Millions of people will be killed in Moscow. Now is the time to push the button.

Petrov refuses to believe it has come this far and stays convinced that the detected launches are a malfunctioning satellite or computer error. Despite the operators confirm that the missile detection system works properly, he confirms to higher command that the alert is a fals alarm.

 

Petrov was right and prevented a worldwide nuclear war that would have destroyed all large cities in both the US and the Soviet Union. This makes him one of the most important persons in the 20th century. As it later turned out, the false alarm was triggered by the sun that scattered on high altitude clouds.

Stanislav Petrov 2014

Unfortunately, the Kremlin wasn't that happy. By breaking a critical military protocol, Petrov risked millions of Soviet lives. He was sent into early retirement with a small pension and suffered a nervous breakdown. It was only in 1998 that a book, written by another officer in that bunker, revealed the story of this heroic man.
 

In 2006, Stanislav Petrov was honored by the United Nations in New York and received the World Citizen Award. Some of his trip to the United States was filmed and later used in the 2014 documentary movie The Man Who Saved the World that featured Stanislav Petrov himself and his translator Galina Kalinina. Stanislav Petrov passed away in Fryazino near Moscow in 2017, aged 77.

More about Petrov in this BBC news article with video, on WashingtonPost.com and the Brightstarsound tribute page.

There's more related info on this blog. The Soviet Око program with the УС-К  and УС-КС satellites in Russia’s Modern Early Warning Systems. This was not the first or worst nuclear incident, as you can read in 1983 - The Brink of Apocalypse, but it sure could have ended as the worst ever incident in history of human civilisation. Meanwhile, US Strategic Intelligence on the USSR. seriously miscalculated the Soviet nuclear intentions, fueling the race for nukes.

 

The Man Who Saved The World