page_title: Anti-submarine warfare
section_title: Anti-submarine warfare technologies
hierarchical_section_title: Anti-submarine warfare / Modern warfare / Anti-submarine warfare technologies
caption_attribution_description: English: One of two U.S. Naval Air System Command’s (NAVAIR) MH-60R “Knighthawk” helicopters conducts an airborne low frequency sonar (ALFS) operation during testing and evaluation at the Atlantic Undersea Test and Evaluation Center (AUTEC). Pilots logged 126 hours on the two helicopters in three weeks and captured all of the data required by the test plan.
context_page_description: Anti-submarine warfare is a branch of underwater warfare that uses surface warships, aircraft, or other submarines to find, track, and deter, damage, or destroy enemy submarines.
  Successful anti-submarine warfare depends on a mix of sensor and weapon technology, training, and experience. Sophisticated sonar equipment for first detecting, then classifying, locating, and tracking the target submarine is a key element of ASW. To destroy submarines, both torpedoes and naval mines are used, launched from air, surface, and underwater platforms. ASW also involves protecting friendly ships.
context_section_description: There are a large number of technologies used in modern anti-submarine warfare:
  Sensors
  Acoustics particularly in active and passive sonar, sonobuoys, and fixed hydrophones aid in the detection of radiated noise. Sonar can be mounted on the hull or in a towed array.
  Pyrotechnics in the use of markers, flares and explosive devices
  Searchlights
  Radar, for surfaced parts
  Hydrodynamic pressure wave (wake) detection
  Laser detection and ranging of surfaced vessels; airborne and satellite
  Electronic countermeasures and acoustic countermeasures such as noise and bubble makers
  Passive acoustic countermeasures such as concealment and design of sound-absorbing materials to coat reflecting underwater surfaces
  Magnetic anomaly detection (MAD)
  Active and (more commonly) passive infra-red detection of surfaced parts.
  In modern times forward looking infrared (FLIR) detectors have been used to track the large plumes of heat that fast nuclear-powered submarines leave while rising to the surface. FLIR devices are also used to see periscopes or snorkels at night whenever a submariner might be incautious enough to probe the surface.
  The active sonar used in such operations is often of "mid-frequency", approximately 3.5 kHz. Because of the quietening of submarines, resulting in shorter passive detection ranges, there has been interest in low frequency active for ocean surveillance. However, there have been protests about the use of medium and low frequency high-powered active sonar because of its effects on whales. Others argue the high power level of some LFA (Low Frequency Active) sonars is actually detrimental to sonar performance in that such sonars are reverberation limited.
caption: An MH-60R conducts an airborne low frequency sonar (ALFS) operation during testing and evaluation.
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