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Towed array sonar

 
Towed Array Sonar

 
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Towed array sonar
 
 
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A towed array sonar is a sonar
Sonar

Sonar is a technique that uses sound propagation to navigation, communicate with or detect other vessels. There are two kinds of sonar: active and passive....
 array that is towed behind a submarine
Submarine

A submarine is a watercraft capable of independent operation below water. It differs from a submersible, which has only limited underwater capability....
 or surface ship
Ship

A ship is a large watercraft that floats on water. Ships are generally distinguished from boats based on size. Ships may be found on lakes, seas, and rivers and they allow for a variety of activities, such as the ferry or cargo ships, fishing, cruise ship, Coast guard, and warship....
. It is basically a long cable, up to 2000 m
Metre

The metre or meter is a Unit of measurement of length. It is the SI base unit of length in the metric system and in the International System of Units , used around the world for general and scientific purposes....
, with hydrophone
Hydrophone

A hydrophone is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates electricity when subjected to a pressure change....
s that is trailed behind the ship when deployed. The hydrophones are placed at equal distance on the cable. On the first few hundred meters near the ship's propeller
Propeller

A propeller is a type of fan which transmits power by converting rotational motion into thrust. It can be used to drive an fixed-wing aircraft, ship, or the fluid within a pump....
 there are usually none since their effectivity would have been reduced by noise and turbulence generated by the propulsion.






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A towed array sonar is a sonar
Sonar

Sonar is a technique that uses sound propagation to navigation, communicate with or detect other vessels. There are two kinds of sonar: active and passive....
 array that is towed behind a submarine
Submarine

A submarine is a watercraft capable of independent operation below water. It differs from a submersible, which has only limited underwater capability....
 or surface ship
Ship

A ship is a large watercraft that floats on water. Ships are generally distinguished from boats based on size. Ships may be found on lakes, seas, and rivers and they allow for a variety of activities, such as the ferry or cargo ships, fishing, cruise ship, Coast guard, and warship....
. It is basically a long cable, up to 2000 m
Metre

The metre or meter is a Unit of measurement of length. It is the SI base unit of length in the metric system and in the International System of Units , used around the world for general and scientific purposes....
, with hydrophone
Hydrophone

A hydrophone is a microphone designed to be used underwater for recording or listening to underwater sound. Most hydrophones are based on a piezoelectric transducer that generates electricity when subjected to a pressure change....
s that is trailed behind the ship when deployed. The hydrophones are placed at equal distance on the cable. On the first few hundred meters near the ship's propeller
Propeller

A propeller is a type of fan which transmits power by converting rotational motion into thrust. It can be used to drive an fixed-wing aircraft, ship, or the fluid within a pump....
 there are usually none since their effectivity would have been reduced by noise and turbulence generated by the propulsion. Surface ships often have the sonar array mounted on a cable which pulls a tow vehicle (an ROV - see Surveillance Towed Array Sensor System
Surveillance Towed Array Sensor System

The AN/UQQ-2 Surveillance Towed Array Sensor System is a Towed array sonar sonar system of the United States Navy.SURTASS systems developed in the 1980s were deployed on Stalwart class tactical auxiliary general ocean surveillance ships and were passive, receive only sonar systems....
) behind the mother ship, or on another cable which trails from the ROV connector. By changing the ROV's depth, the sensor can be deployed in different thermal layers
Thermocline

The thermocline is a thin but distinct layer in a large body of fluid , in which temperature changes more rapidly with depth than it does in the layers above or below....
.

Akula Class Submarine
The array's hydrophones can be used to detect sound sources, but the real value of the array is that the signal processing
Signal processing

Signal processing is the analysis, interpretation, and manipulation of signal . Signals of interest include: audio signal processing, , time-varying measurement values and sensor data, for example biological data such as electrocardiograms, control system signals, telecommunication transmission signals such as radio signals, and many others....
 technique of beamforming
Beamforming

Beamforming is a signal processing technique used in sensor arrays for directional signal transmission or reception. This spatial selectivity is achieved by using adaptive or fixed receive/transmit beampatterns....
 and interferometry
Interferometry

Interferometry is the technique of diagnosing the properties of two or more waves by studying the pattern of interference created by their Superposition principle....
 can be used to calculate the distance and the direction of a sound source. For this, the relative position of the hydrophones need to be known, usually this is only guaranteed when the cable of the array is in a straight line. Therefore, a vessel using a towed array will need to travel straight (and level), lest a change of course will disturb the array and reduce its effectiveness. Also it has to reduce its speed because the hydrodynamic drag
Drag (physics)

The term drag is widely used in Physics and Engineering and is central to the field of fluid dynamics. "Drag" refers to forces that oppose the motion of a solid object through a fluid ....
 might tear the cable - this can also happen if the array makes contact with the seafloor or the submarine operates astern propulsion
Astern propulsion

Astern propulsion is a maneuver in which a ship's propelling mechanism is used to develop thrust in a retrograde direction. Astern propulsion does not necessarily imply the ship is moving astern ; astern propulsion is used to slow a ship by applying a force in the direction of the stern of the ship, instead of the bow ....
.

Despite all those disadvantages, a towed array is useful since it offers better resolution and range compared to a hull mounted sonar and it covers the baffles
Baffles (submarine)

The baffles is the area in the water directly behind a submarine or ship through which a hull -mounted sonar cannot hear. Since the sonar array is extremely sensitive to underwater sounds, it must be protected from the noise generated by machinery on the vessel using the sonar....
, the blind spot of hull mounted sonar.

See also

  • Sonar
    Sonar

    Sonar is a technique that uses sound propagation to navigation, communicate with or detect other vessels. There are two kinds of sonar: active and passive....
  • Aperture synthesis
    Aperture synthesis

    Aperture synthesis or synthesis imaging is a type of interferometry that mixes signals from a collection of telescopes to produce images having the same angular resolution as an instrument the size of the entire collection....
  • Synthetic aperture sonar
    Synthetic aperture sonar

    Synthetic aperture sonar is a form of sonar in which sophisticated post-processing of sonar data are used in ways closely analogous to synthetic aperture radar....
  • Phased array
    Phased array

    This article is about general theory and electromagnetic phased array.'For the ultrasonic and medical imaging application, see phased array ultrasonics....
  • Surveillance Towed Array Sensor System
    Surveillance Towed Array Sensor System

    The AN/UQQ-2 Surveillance Towed Array Sensor System is a Towed array sonar sonar system of the United States Navy.SURTASS systems developed in the 1980s were deployed on Stalwart class tactical auxiliary general ocean surveillance ships and were passive, receive only sonar systems....
     (SURTASS)