DRDO makes Navy 'see' in the water

Written by Huma Siddiqui | Updated: Dec 2 2013, 13:58pm hrs
If you have watched some of the widely acclaimed submarine movies such as U-571, Das Boot or The Hunt For Red October, youll recall how navy personnel manning underwater war machines have used sonar technology to navigate and detect objects on or under the surface of the water, such as other vessels. Sonar, an underwater equivalent of radar, is used to find and identify objects in water. It is also used to determine water depth and is applied to water-based activities because sound waves attenuate (taper off) less in water as they travel than do radar and light waves.

The modern anti-submarine warfare demands sensor deployment from surface, sub-surface and air. Gone are the days when sonar equipment for the Indian Navy used to be imported from Russia, Germany and Poland. In the last few years, this has become a key area of focus for the Defence Research and Development Organisation (DRDO), the endeavour being to make the country self-reliant in this technology.

A key DRDO laboratory located in Kochi, called the Naval Physical and Oceanographic Laboratory (NPOL), is taking rapid strides in the design and development of underwater surveillance systems. Commencing with advanced panoramic sonar hull mounted (APSOH) in 1983, NPOL has delivered several sonar systems, such as Panchendriya, Humsa, Mihir, etc, which have been fitted on to submarines, surface ships and airborne platforms of Indian Navy. The operational utility of these systems has provided impetus for further improvement and development of new configurations of underwater systems in tune with global standards, DRDO officials inform.

The core competence of NPOL is in the areas of oceanography, electro-acoustic transducers, signal processing and systems engineering. Over the years, the institute has established several infrastructure facilities for carrying out defence R&D activities related to sonar systems. It owns a marine acoustic research vessel named as INS Sagardhwani. The vessel is run and maintained by the Indian Navy for DRDO and based at Southern Naval Command, Kochi.

This ship has got many special facilities for conducting underwater ocean environmental and acoustic experiments both in shallow and deep waters. Modern equipments are fitted on-board in order to pursue research in oceanography and acoustics. The ships laboratories house all scientific equipment to make high resolution oceanographic and acoustics measurements at the sea. The ship can moor oceanographic and acoustic buoys in shallow and deep waters.

For the uninitiated, sonar is an acronym for sound navigation and ranging. The principle involves bouncing acoustic waves off of objects, and determining their distances by measuring the time for the echoes to return. Sonar is commonly used on board ships and boats to measure the depths of bodies of water. It can also be used to locate underwater objects such as fish, submarines etc.

A complete sonar set has several components, including an acoustic pulse generator, a transducer for transmitting acoustic waves in narrow beams, an acoustic pickup, a set of amplifiers and an indicating display. The distance to an object depends on the echo delay. For sonar to be accurate, the speed of sound in the medium must be known.

Precision sonar equipment can rival machine vision for mapping and navigation. A high-level sonar set can differentiate among objects in its vicinity. This ability to distinguish individual objects, also called targets, from one another is called the resolution. In order for a sonar set to have high resolution, the acoustic-wave beam must be narrow, and it must be swept around in two or three dimensions.

Prior to the advent of sonar, mariners used lead lines to take systematic soundings of the seafloor, which enabled them to produce early depth charts. Sonar was first used during World War I to detect submarines. By the 1920s, the US Coast and Geodetic Surveythe precursor to NOAAs National Ocean Servicewas using it to map deep-water areas. The technology steadily improved, and by World War II, was used once again for military purposes.

Cut to present, and to Indias achievements to be precise. According to DRDO officials, the design of sonar requires expertise in sensor technology, signal conditioning and processing, electronic packaging, materials technology, ocean acoustics and mechanical engineering. Today NPOL stands out with great pride for its outstanding achievements and contributions in the areas of sonar research and development for Navy. Indigenously developed Tadpole sonobuoys have been extensively used by Navy in their airborne sonar operations. These developments have resulted in establishment of exclusive production lines in Bharat Electronics and other industries in the last few years.

NPOL has also developed advanced display and signal processing hardware and software with advanced algorithms put in place. Take for instance, a cost-effective commercial off-the-shelf (COTS) hull mounted sonar simulator system for imparting hands-on realistic training on various functionalities and operational details of the sonar to sailors and operators. The PC-based generic sonar simulator is a real-time system with one instructor station and multiple trainee stations. There is provision for setting scenarios from instructor station. All the trainees can set processing modes and display formats for any given scenario.

Among other things, Tarangini is a device for determining the underwater depth and bottom hardness of shallow water bodies. It is a simple and reliable equipment which provides information about depth in terms of feet, limited to an operational range of 100 feet. In any underwater search and rescue operation, one of the basic requirements is the determination of the depth of the water body, either at predetermined locations or during a site scan. This requirement is more pronounced in the case of civilian organisations like fire force, disaster management teams, social clubs and adventure clubs who provide emergency help in case of accidents involving drowning of people in inland water bodies like lakes, ponds, canals etc.

DRDO is definitely leaving no stone unturned to see in the water. Watch out for the sound of things to come!