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Navy’s eyes and ears | idrw.org
THE Naval Physical and Oceanographic Laboratory (NPOL), Kochi, aims at perfection. Take for instance the system integration rig on its wooded campus. It is a small room, rigged up to look like a cabin in the Indian Navys warship, with several pieces of sonar equipment, operators cubicles, computer consoles, and so on. Not only is the cabins ambience similar to that of a ships cabin but even the lighting is low as in a vessel. The sonars narrow cubicles with consoles resemble those in a warship.
This year, 2012, is the golden jubilee of the NPOL. Originally named the Indian Naval Physical Laboratory, it was set up in 1952 and became part of the DRDO in 1958. It was re-christened NPOL in 1967.
S. Anantha Narayanan, Director, NPOL, said, Our vision is to be a centre of excellence in underwater sensors and surveillance systems. This is a niche area. Nobody else in this country is working on underwater sensors and surveillance systems. The NPOLs mission is to design, develop and integrate sonar systems for installation in the Navys ships and submarines. The NPOL fosters the technologies, which will enable the development of sonars and associated material, and increase the understanding of ocean environment. It has partnered with the Naval Science and Technological Laboratory (NSTL) in developing an anti-torpedo defence system called Mareech, which includes a sensor array and a decoy.
The NPOL specialises in anti-submarine warfare oceanography, which essentially is about how sound waves propagate under water in various temperature, pressure and salinity conditions. That study is done exclusively by the NPOL, and it has an important bearing on the capability of the sonar systems that the country builds, Anantha Narayanan said.
Sonars are early warning systems that help in the location of enemy vessels, submarines, torpedoes and sea mines. Anantha Narayanan described sonars as essentially underwater radars. Developing sonars is more complex compared with radars because it requires understanding the oceans depth, salinity and temperature. While a radar uses electromagnetic waves to warn of incoming enemy aircraft or missiles, sonars use acoustic waves to warn of threats from hostile ships/submarines and torpedoes. (Electromagnetic waves get attenuated quickly in water). Transducers convert the electrical energy into acoustic energy, which propagates in water. This is processed and the findings are displayed on the operators console for interpretation. By listening to the noise coming from under water, an experienced operator can figure out whether it belongs to a ship, a submarine or a torpedo.
Sonars are of two types: passive and active. A passive sonar picks up the radiated noise from a hostile submarine, a torpedo or schools of fish, interprets the direction in which it is coming and identifies the target. From the noise that an engine or a propeller in a ship, submarine or torpedo makes, sonars can make out their attributes. They pick up that signature, track it and thus find out the direction in which the object is moving, calculate its speed and also help in classifying it as a friend or foe. An Active sonar pumps energy into the water, waits for the echo, and thus helps in finding out the distance at which the object is travelling. active sonars are fitted on ships so that they can hunt for submarines. Submarines use passive sonars so that they can pick up the noise from ships without their (submarines) getting exposed. Sonars can be deployed from air, with helicopters lowering the transducers into water.
In the 1980s, the NPOL came up with a hull-mounted sonar called Advanced Panoramic Sonar Hull (APSOH). It was the first indigenously designed and developed ship-borne sonar system for active ranging, passive listening, auto-tracking of targets and their classification. Then it developed HUMSA (Hull Mounted Sonar Advanced), which helped naval vessels track their targets in shallow and deep waters and proved its efficiency for about 10 years even in the highly variable tropical waters.
The NPOL has now developed HUMSA-NG (new generation) and S. Kedarnath Shenoy, scientist, is its architect. The project was completed in just four years from the drawing board to tests, fitment on a vessel and evaluation, said Anantha Narayanan. He added: It is a third-generation sonar for surface ships that the NPOL is making. There lies the message. The message is that it disproves the notion that the DRDO delayed the projects, he said. APSOH took seven years to develop, HUMSA five and HUMSA-NG less than four years. So the learning curve has enabled us to deliver the products in time, and right now we are ahead of the [availability of the] ships, the Director added.
Shenoy said that out of 10 HUMSA-NG sonars delivered to the Navy since 2009, three were installed on its ships and the integration of one was under way. Besides these 10 sonars, the Navy has placed orders for six HUMSA-NG sonars. They would be installed on destroyers, frigates and corvettes. Another sonar developed by the NPOL for installation on the Navys EKM class of submarines is called USHUS. Besides detecting and tracking enemy submarines, vessels and torpedoes, it can be used for underwater communication and for avoiding obstacles.
R. Kanakarajan, Associate Director, NPOL, said the current trend in the passive sonars deployed on submarines was to work towards low frequencies. As we go down in frequency, the size of the sonar sensor array goes up. There are contradictory requirements: sonars should be compact, they should have low frequency and high power and should be light. These are the challenges we face when we work under water in dynamic conditions, said Kanakarajan.
Mihir is the sonar deployed from helicopters. Its transducer is dunked under water. DRDO literature says that this sonar has been designed for the Armys Advanced Light Helicopter (ALH) where weight, space and power are at a premium. The system consists of a sonar dome, acoustic and environmental sensors, a winching system, a signal conditioner and processor, a very high frequency receiver and antenna. The transducer converts the electrical energy into acoustic energy and the echo is available on display in the computer for the operator to interpret. The area covered is more because a helicopter can lower the transducer in one location, sanitise it and fly elsewhere for deploying the transducer again.
The NPOL has developed a Towed Array Data Sonar System (to detect submarines and torpedoes) in which the array alone is 200 metres long and the cable attached to it is a kilometre long. The cable and the array will be mutually buoyant. For the past seven years, the NPOL has been working on Micro-Electro-Mechanical Systems (MEMS). It has developed a miniaturised underwater acoustic sensor called hydrophone, which is the equivalent of a microphone in hand. Its architect is V. Natarajan, Project Director, MEMS Regional Centre, NPOL. This hydrophone is based on metal-oxide-semiconductor field-effect transistor (MOSFET) and a piezo-electric sensor. The sensor measures less than one inch by one inch and weighs less than 32 grams. These miniature sensors find applications in thin-lined towed arrays for submarines, ships and unmanned surface vehicles. Natarajan said the centre had developed a conductivity, temperature and depth sensor to measure the temperature, salinity and depth of the ocean because the speed of sound in the ocean depends on these parameters and they influence the sonars performance. This sensor is totally indigenous, Natarajan said.
Sameer Abdul Azeez, scientist, NPOL, has built a novel device called Tarangini, which helps rescuers to know the depth of a waterbody and the hardness of its bed. What motivated Azeez to build the contraption was the fact that a number of people drowned in waterbodies formed by abandoned quarries in Kerala.
We are a highly focussed laboratory. We dont do anything outside underwater surveillance, Anantha Narayanan said. In the Twelfth Plan period (2012-17), the NPOL plans to concentrate on an anti-submarine warfare suite for ships, fourth-generation HUMSA and second-generation Mareech. We are in continuous upgrade mode because the life of a sonar system is not more than 10 to 15 years, he said.
THE Naval Physical and Oceanographic Laboratory (NPOL), Kochi, aims at perfection. Take for instance the system integration rig on its wooded campus. It is a small room, rigged up to look like a cabin in the Indian Navys warship, with several pieces of sonar equipment, operators cubicles, computer consoles, and so on. Not only is the cabins ambience similar to that of a ships cabin but even the lighting is low as in a vessel. The sonars narrow cubicles with consoles resemble those in a warship.
This year, 2012, is the golden jubilee of the NPOL. Originally named the Indian Naval Physical Laboratory, it was set up in 1952 and became part of the DRDO in 1958. It was re-christened NPOL in 1967.
S. Anantha Narayanan, Director, NPOL, said, Our vision is to be a centre of excellence in underwater sensors and surveillance systems. This is a niche area. Nobody else in this country is working on underwater sensors and surveillance systems. The NPOLs mission is to design, develop and integrate sonar systems for installation in the Navys ships and submarines. The NPOL fosters the technologies, which will enable the development of sonars and associated material, and increase the understanding of ocean environment. It has partnered with the Naval Science and Technological Laboratory (NSTL) in developing an anti-torpedo defence system called Mareech, which includes a sensor array and a decoy.
The NPOL specialises in anti-submarine warfare oceanography, which essentially is about how sound waves propagate under water in various temperature, pressure and salinity conditions. That study is done exclusively by the NPOL, and it has an important bearing on the capability of the sonar systems that the country builds, Anantha Narayanan said.
Sonars are early warning systems that help in the location of enemy vessels, submarines, torpedoes and sea mines. Anantha Narayanan described sonars as essentially underwater radars. Developing sonars is more complex compared with radars because it requires understanding the oceans depth, salinity and temperature. While a radar uses electromagnetic waves to warn of incoming enemy aircraft or missiles, sonars use acoustic waves to warn of threats from hostile ships/submarines and torpedoes. (Electromagnetic waves get attenuated quickly in water). Transducers convert the electrical energy into acoustic energy, which propagates in water. This is processed and the findings are displayed on the operators console for interpretation. By listening to the noise coming from under water, an experienced operator can figure out whether it belongs to a ship, a submarine or a torpedo.
Sonars are of two types: passive and active. A passive sonar picks up the radiated noise from a hostile submarine, a torpedo or schools of fish, interprets the direction in which it is coming and identifies the target. From the noise that an engine or a propeller in a ship, submarine or torpedo makes, sonars can make out their attributes. They pick up that signature, track it and thus find out the direction in which the object is moving, calculate its speed and also help in classifying it as a friend or foe. An Active sonar pumps energy into the water, waits for the echo, and thus helps in finding out the distance at which the object is travelling. active sonars are fitted on ships so that they can hunt for submarines. Submarines use passive sonars so that they can pick up the noise from ships without their (submarines) getting exposed. Sonars can be deployed from air, with helicopters lowering the transducers into water.
In the 1980s, the NPOL came up with a hull-mounted sonar called Advanced Panoramic Sonar Hull (APSOH). It was the first indigenously designed and developed ship-borne sonar system for active ranging, passive listening, auto-tracking of targets and their classification. Then it developed HUMSA (Hull Mounted Sonar Advanced), which helped naval vessels track their targets in shallow and deep waters and proved its efficiency for about 10 years even in the highly variable tropical waters.
The NPOL has now developed HUMSA-NG (new generation) and S. Kedarnath Shenoy, scientist, is its architect. The project was completed in just four years from the drawing board to tests, fitment on a vessel and evaluation, said Anantha Narayanan. He added: It is a third-generation sonar for surface ships that the NPOL is making. There lies the message. The message is that it disproves the notion that the DRDO delayed the projects, he said. APSOH took seven years to develop, HUMSA five and HUMSA-NG less than four years. So the learning curve has enabled us to deliver the products in time, and right now we are ahead of the [availability of the] ships, the Director added.
Shenoy said that out of 10 HUMSA-NG sonars delivered to the Navy since 2009, three were installed on its ships and the integration of one was under way. Besides these 10 sonars, the Navy has placed orders for six HUMSA-NG sonars. They would be installed on destroyers, frigates and corvettes. Another sonar developed by the NPOL for installation on the Navys EKM class of submarines is called USHUS. Besides detecting and tracking enemy submarines, vessels and torpedoes, it can be used for underwater communication and for avoiding obstacles.
R. Kanakarajan, Associate Director, NPOL, said the current trend in the passive sonars deployed on submarines was to work towards low frequencies. As we go down in frequency, the size of the sonar sensor array goes up. There are contradictory requirements: sonars should be compact, they should have low frequency and high power and should be light. These are the challenges we face when we work under water in dynamic conditions, said Kanakarajan.
Mihir is the sonar deployed from helicopters. Its transducer is dunked under water. DRDO literature says that this sonar has been designed for the Armys Advanced Light Helicopter (ALH) where weight, space and power are at a premium. The system consists of a sonar dome, acoustic and environmental sensors, a winching system, a signal conditioner and processor, a very high frequency receiver and antenna. The transducer converts the electrical energy into acoustic energy and the echo is available on display in the computer for the operator to interpret. The area covered is more because a helicopter can lower the transducer in one location, sanitise it and fly elsewhere for deploying the transducer again.
The NPOL has developed a Towed Array Data Sonar System (to detect submarines and torpedoes) in which the array alone is 200 metres long and the cable attached to it is a kilometre long. The cable and the array will be mutually buoyant. For the past seven years, the NPOL has been working on Micro-Electro-Mechanical Systems (MEMS). It has developed a miniaturised underwater acoustic sensor called hydrophone, which is the equivalent of a microphone in hand. Its architect is V. Natarajan, Project Director, MEMS Regional Centre, NPOL. This hydrophone is based on metal-oxide-semiconductor field-effect transistor (MOSFET) and a piezo-electric sensor. The sensor measures less than one inch by one inch and weighs less than 32 grams. These miniature sensors find applications in thin-lined towed arrays for submarines, ships and unmanned surface vehicles. Natarajan said the centre had developed a conductivity, temperature and depth sensor to measure the temperature, salinity and depth of the ocean because the speed of sound in the ocean depends on these parameters and they influence the sonars performance. This sensor is totally indigenous, Natarajan said.
Sameer Abdul Azeez, scientist, NPOL, has built a novel device called Tarangini, which helps rescuers to know the depth of a waterbody and the hardness of its bed. What motivated Azeez to build the contraption was the fact that a number of people drowned in waterbodies formed by abandoned quarries in Kerala.
We are a highly focussed laboratory. We dont do anything outside underwater surveillance, Anantha Narayanan said. In the Twelfth Plan period (2012-17), the NPOL plans to concentrate on an anti-submarine warfare suite for ships, fourth-generation HUMSA and second-generation Mareech. We are in continuous upgrade mode because the life of a sonar system is not more than 10 to 15 years, he said.
