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SOSUS, an acronym for sound surveillance system, is a chain of underwater listening posts located around the world in places such as the Atlantic Ocean near Greenland, Iceland and the United Kingdom—the GIUK gap—and at various locations in the Pacific Ocean. The United States Navy's initial intent for the system was for tracking Soviet submarines,[1] which had to pass through the gap to attack targets further west. It was later supplemented by mobile assets such as the Surveillance Towed Array Sensor System (SURTASS), and became part of the Integrated Undersea Surveillance System (IUSS).


SOSUS history began in 1949 when the US Navy formed the Committee for Undersea Warfare to research anti-submarine warfare. The panel allocated US$10 million (equivalent to $105 million today) annually to develop systems to counter the Soviet submarine threat consisting primarily of a large fleet of diesel submarines. They decided on a system to monitor low-frequency sound in the SOFAR channel using multiple listening sites equipped with hydrophones and a processing facility that could detect submarine positions by triangulation[dubious ] over hundreds of miles.


At MIT in 1950, the committee sponsored Project Hartwell, named for the Hartwell Farms restaurant in Lexington, Massachusetts, where some of the initial steps were planned.[2] In November, they selected Western Electric to build a demonstration system, and the first six-element hydrophone array was installed on the island of Eleuthera in the Bahamas. Meanwhile, Project Jezebel at Bell Labs and Project Michael at Columbia University focused on studying long range acoustics in the ocean.

By 1952, enough progress resulted in top secret plans to deploy six arrays in the North Atlantic basin, and the classified name SOSUS was used. The number of arrays was increased to nine later in the year, and Royal Navy and US Navy ships, including USS Neptune and USS Peregrine, started laying the cabling under the cover of Project Caesar. In 1953, Jezebel's research had developed an additional high-frequency system for direct plotting of ships passing over the stations, intended to be installed in narrows and straits, called Project Colossus.


First SOSUS sensors

SOSUS systems consisted of bottom-mounted hydrophone arrays connected by underwater cables to facilities ashore. The individual arrays were installed primarily on continental slopes and seamounts at locations optimized for undistorted long range acoustic propagation. The combination of location within the ocean and the sensitivity of arrays allowed the system to detect acoustic power of less than a single watt at ranges of several hundred kilometres. SOSUS monitoring stations went by the acronym NOPF.

When the USS Thresher (SSN-593) sank in 1963, SOSUS helped determine its location. In 1968, the first detections of Victor and Charlie class Soviet submarines were made, while in 1974 the first Delta class submarine was observed. In 1968, SOSUS played a key role in locating the wreckage of a US Nuclear Attack submarine, the USS Scorpion (SSN-589), lost near the Azores in May. Moreover, SOSUS data from March 1968 facilitated the discovery, and clandestine retrieval six years later, of parts of a Soviet GOLF II-class ballistic missile submarine, the K-129, that foundered that month north of Hawaii.[3]

Given its criticality to Cold War operations against the Soviet Navy's submarine fleet, SOSUS/IUSS remained highly classified from its inception and the purposes and activities of the various NAVFACs were not publicly acknowledged nor commonly known outside of the US Navy's submarine fleet, its cruiser/destroyer/frigate fleet, and its anti-submarine warfare aircraft forces until the end of the Cold War. In 1991, the system mission was declassified and in 1993 a program reporting whale detections was started. The Advanced Deployable System became operational as part of IUSS in 1996.


In 1988, Stephen Joseph Ratkai, a Hungarian-Canadian recruited by Soviet Intelligence, was arrested, charged and convicted in St. John's, Newfoundland for attempting to obtain information on the SOSUS site at Naval Station Argentia. John Anthony Walker, a US Navy Chief Warrant Officer and communications specialist, divulged SOSUS operational information to the Soviet Union during the Cold War which compromised its effectiveness.[4]

Post-Cold War[edit]

SOSUS was gradually condensed into a smaller number of monitoring stations during the 1970s and 1980s. However, the SOSUS arrays themselves were based upon technology that could only be upgraded irregularly. With the ending of the Cold War in the 1990s, the immediate need for SOSUS decreased, and the focus of the US Navy also turned toward a system that was deployable on a theatre basis.[3] Although officially declassified in 1991, by that time IUSS and SOSUS had long been an open secret.[3]

Alternate users[edit]

Alternate or dual-use partnerships exist with the University of Washington Applied Physics Laboratory[5] for Ocean Acoustic Tomography, National Oceanic and Atmospheric Administration (NOAA) Vents,[6] Woods Hole Oceanographic Institute,[7] Texas Applied Research Laboratories,[8] and several other organizations.

Underwater Great Wall[edit]

The People's Republic of China maintains a submarine monitoring system in the South China Sea, called the "Great Underwater Wall" (Chinese: 水下长城) and the "Underwater Monitoring System" (Chinese: 水下监听系统) in Chinese media.[9]

China has been operating two underwater sensors since 2016, located in the Challenger Deep and off the island of Yap, Micronesia.[10][11] The sensors reportedly have the acoustic range to detect movement at Naval Base Guam, and reportedly may allow China to monitor the movements of the US Navy, including its submarines.[10]

See also[edit]


  1. ^ Di Mento, John Mark (December 2006). "Environmental Challenges to Post-Cold War Naval Operations: The Browning of the Blue Water Battlespace". Beyond the Water's Edge: United States National Security & the Ocean Environment (Ph.D. thesis). Medford, MA: Fletcher School of Law and Diplomacy, Tufts University. pp. 255–256. Document No. 3262885 – via ProQuest Dissertations Publishing.
  2. ^ Goldstein, Jack S (1992). A different sort of time: the life of Jerrold R. Zacharias, scientist, engineer, educator. MIT Press. p. 338.
  3. ^ a b c "SOSUS The "Secret Weapon" of Undersea Surveillance". Undersea Warfare. Vol. 7 no. 2. US Navy. Winter 2005. Archived from the original on 2013-12-19. Retrieved 2013-12-13.
  4. ^ Keller, Bill (1985). "Spy Case is Called Threat to Finding Soviet Submarines". The New York Times.
  5. ^ Blue Water Acoustic Research at APL-UW
  6. ^ "NOAA PMEL Acoustics Program". NOAA. Retrieved 2013-12-13.
  7. ^ "Autonomous Hydrophone Array (AHA)". Woods Hole Oceanographic Institution. 2012-02-03. Retrieved 2013-12-13.
  8. ^ "Ongoing Research at ARL:UT". University of Texas at Austin Applied Research Laboratories. Retrieved 2013-12-13.
  9. ^ Sutton, H.I. (May 27, 2018). "Good Wind ears: China's Underwater Great Wall". The network is termed 'Underwater Great Wall' (水下长城) and 'Underwater Monitoring System' (水下监听系统) in Chinese media, as well as 'Good wind ears' (顺风耳 - Omniscient, all-knowing) and has a program cost of 2bn Yuan (313m US Dollars).
  10. ^ a b Chen, Stephen (January 22, 2018). "Surveillance under the sea: how China is listening in near Guam". South China Morning Post. Retrieved January 23, 2018.
  11. ^ Trevithick, Joseph (January 23, 2018). "China Reveals It Has Two Underwater Listening Devices Within Range of Guam". The Drive. Retrieved January 23, 2018.

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