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KOPO Korabl Osveshchenie Podvodnoy Obstanovki
Ship Illumination Underwater Environment

The Russian Navy has a class of ships with no direct American counterpart. These very un-american ships are the KOPO - Korabl Osveshchenie Podvodnoy Obstanovki [Ship Illumination Underwater Environment]. The word "Osveshchenie" is a bit tricky, as it can be rendered as "lighting" [a bit too literal and not not quite right for the underwater environment], or "coverage" [a bit too vague], or "illumination" [which is not perfect is probably the most servicable of the options at hand].

As is well known, the most effective means of searching and detecting underwater objects is sonar equipment. An anti-submarine ship equipped with a hydroacoustic station is designed to search for a submarine in a given area independently or as part of a group of anti-submarine ships.

The general trend of military shipbuilding is a significant reduction in the noise of modern submarines (PL) and, as a result, an increase in the secrecy of their military operations. Detection ranges of low-noise submarines by passive modes of sonar complexes (SAC) decreased from tens to units of kilometers. The increase in the size of the receiving antennas does not give a significant increase in efficiency to the noise-sensing modes of sonar complexes. Therefore, to illuminate the underwater situation in large areas, it is necessary to attract a huge number of search forces and means, which becomes an insoluble problem for the navy.

The disadvantage of this approach is the limited detection range of the submarine due to the high level of traveling acoustic noise and the use of a monostatic sonar mode, that is, the combination of the emitting and receiving antennas, as a result of which the probe signal (ES) is significantly attenuated, passing the distance to the target and back. In addition, given that the submarine detects noise and signals from the surface ships sonar at a distance significantly exceeding the range of its detection by the same sonar, and thereby controls its current location, it is able to effectively avoid detection. As a result, the detection of a submarine by an anti-submarine ship equipped with a sonar station is not effective enough.

The anti-submarine forces of the leading maritime states solve the problem of combating low-noise submarines in the context of the general concept of creating a unified information environment in combat zones by using rapidly deployed, multi-element illumination systems for underwater conditions, the so-called network-centric systems.

The underwater illumination system provides the command with a complete picture of the underwater situation in the war zone and provides target designation to designated anti-submarine forces. Any low-noise submarine is detected when elements of the illumination system of the underwater environment get into the coverage area.

There is a method of illumination an underwater environment by deploying in a given area a system of autonomous sonar stations (AGAS) detecting moving objects. This system is one of the elements of the underwater illumination system and is a set of autonomous receiving stations for the detection and classification of underwater objects with the transmission of information via radio or sonar channel. The system is deployed either in the area of ??anticipated enemy submarine actions, or in the form of a line to control underwater space in the direction of probable enemy movement. One set of the AGAS system includes several dozen stations installed at anchors at depths of several hundred meters.

The setting method does not differ from the known methods for setting up sonar buoys, for example, from anti-submarine aircraft or surface ships. AGAS functioning time can be up to 6 months. AGAS solves the problem of detecting, classifying and determining the direction to the target in the noise-detecting mode and transmitting this information to the observer ship. For this, AGAS is equipped with a directional passive antenna and a radiator for transmitting information through the sonar channel. Other autonomous hydroacoustic stations of a similar method for illumination underwater conditions are known.

The disadvantage of the method of illumination the underwater environment using these devices is the small detection range in the noise detection mode, and to control a large water area requires the setting of a large number of stations to ensure the required efficiency of the illumination system of the underwater situation. There is a method of illuminating the underwater environment by quickly deploying special vessels, for example, the American T-AGOS type, equipped with the sonar station AN / UQQ-2 (SURTASS) in specified areas of the oceans. These surface ships belong to the class of vessels for long-range sonar observation (NK DGN). This method of searching the underwater environment is to organize a search for submarines in a given area when the hydroacoustic station is in noise-detecting mode. The AN/UQQ-2 uses a 1220 m long flexible towed antenna (HBA), which can be pulled aft on the cable and towed in the depth range 150-450 meters. This system was effective while noisy submarines were quite large and the detection range reached 200 km.

However, due to the decrease in the noise of submarines in recent decades by several times, their detection ranges in the passive mode have decreased to units of kilometers. In this regard, NK DGN began to apply an active-passive method of illumination the underwater situation, which consists in using a towed emitter in the SURTASS system.

The disadvantages of this method are:

  • low search efficiency of submarines in this way due to the short detection range in the passive mode;
  • fragmentation of the field of view in the active-passive mode, which is formed around the receiving antenna and has the largest detection range in the direction perpendicular to the GPBA line;
  • due to the lack of secrecy of the NK DGN there is a high probability of its destruction by the opposing side.

The SURTASS/LFA - Low Frequency Active (LFA) is an active adjunct to the SURTASS passive capability. Currently, the R/V Cory Chouest is the only ship that has the SURTASS LFA sonar system. LFA compliments SURTASS passive operations by acquiring and tracking submarines in quiet operating modes, measuring accurate target range, and reacquiring lost contacts. This integrated active and passive capability provide Battle Groups with a reliable and continuous maritime picture. It employs a transmit (source) array for monostatic operations (own ship receiving).

Another method of illumination the underwater situation consists in the fact that the submarine armed with a sonar system is additionally equipped with a rapidly deployable multi-element sonar system. Such a system, for example, is the ADS (Advanced Deployable System), which is a bottom fiber-optic sonar array up to 20 km long, covertly installed in a given area by a search submarine, for example, of the Virginia type. At the same time, a relatively flat bottom surface and depth of the sea are required, which allows installation divers to work. Using the ADS system, they detect targets, classify them and determine the coordinates of the targets when it is in passive mode, and upon detection, enable active mode to determine the coordinates of the target. In the active-passive mode of operation, the ADS emits a sounding signal from stationary bottom emitters installed at a distance of 2-3 miles from the ADS axis.

The design of the emitter includes an active antenna part having a small positive buoyancy, and power supplies and generators placed in the anchor device. Power supplies have a limited capacity, so the radiation is produced occasionally only after the establishment of hydroacoustic contact in the noise direction finding mode. having a small positive buoyancy, and power supplies and generators placed in the anchor device. Power supplies have a limited capacity, so the radiation is produced occasionally only after the establishment of hydroacoustic contact in the noise direction finding mode. having a small positive buoyancy, and power supplies and generators placed in the anchor device. Power supplies have a limited capacity, so the radiation is produced occasionally only after the establishment of hydroacoustic contact in the noise direction finding mode. Data on the underwater environment obtained by ADS is transmitted via optical cable to the submarine, where they are integrated with the data of the submarine hull.

According to the test results, it was recognized that the method of illumination the underwater environment, based on the interaction of the submarine and the ADS system, provides the submarine with an increase in the efficiency of illumination the underwater environment through the use of an external sonar system. The transmission of data on the underwater situation to a surface ship or aircraft is carried out over the air. The disadvantages of the method of illumination underwater conditions using the ADS system are:

  • a relatively low detection range of the system, because the main way to view is the passive mode, and the active mode is used to measure the distance to the target according to the primary detection in the passive mode;
  • limited time use of the active mode due to the limited electrical capacity of the power supply;
  • stringent requirements for the installation area of ??the remote sonar antenna on the bottom topography and depth of the place, consisting in the need to install the bottom system on a flat bottom surface and the ability of divers to work at a given depth;
  • the technological complexity of deploying an antenna array and emitter, requiring the use of up to 3 submarines and gliders and up to ten installation divers from the board of the submarine and reducing the ammunition stock of the submarine, due to the need to load ADS and technological equipment;
  • the difficulty of maneuvering the search submarine when receiving data from ADS via fiber optic cable.

The technical problem to be solved is improving the illumination efficiency of the underwater environment in the designated area. The specified technical result is achieved by the fact that a surface ship (the underwater illumination ship, abbreviated as OPO ship) is equipped with hydroacoustic and other means, allowing to create a multistatic sonar system in the designated area with emitter and receivers spaced in space and thereby substantially increase the illuminated area. These tools include:

  • A set of passive autonomous sonar stations (AGS) equipped with an omnidirectional receiving sonar antenna, an antenna orientation control unit in space, a signal processing unit from the hydroacoustic antenna output, and equipment for transmitting detection messages an underwater object of a given class, an electric power source, an anchor with an anchor cable. As the equipment for transmitting a message about the detection of an underwater object of a given class, a radio transmitter with a radio or satellite antenna pop-up for the duration of the message transmission or a sound communication station can be used.
  • A hydro-acoustic emitter (hereinafter referred to as an emitter) with a hydroacoustic antenna (hereinafter referred to as an emitter antenna) lowered under water to a predetermined depth from the side of the OPO ship lying in the drift.
  • Shipborne instruments for measuring the characteristics of hydroacoustic conditions in the navigation area (depth of the area, vertical distribution of the speed of sound, waves of the sea surface).
  • Ship radio and sonar equipment for receiving messages from the AGS.
  • A shipboard computer with a special program that allows, before starting work, to calculate the required number and coordinates (positions) of AGS, as well as the trajectory of maneuvering the ship during the deployment of AGS, and in the process to determine the trajectories of the detected underwater objects and using them to increase the reliability of their classification and accuracy determination of coordinates and parameters of their movement.

The OPO ship allows simultaneously illuminating the underwater situation in an area of ~33,000km2. For existing anti-submarine surface ships, this parameter does not exceed 1,000 km2 .

An integrated control system (ISU) for an underwater illumination (OPO) system consists in combining all ship navigational and electronic weapons into an information-control network system with vertical and, essentially, horizontal connections of information sources, nodes decision making and executive bodies. An approach to integrated control system (ICS) of underwater surveillance ship (USS) design implies the entire navigation and radio-electronic ship weaponry integration into an information- control network system with vertical and especially horizontal connections of information sources, decision blocks and effectors.

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Page last modified: 13-09-2021 17:22:13 ZULU