Advanced Torpedo Defence System (ATDS) ‘Maareech’ was designed and developed by Naval Physical and Oceanographic Laboratory (NPOL), Kochi, to protect surface ships of Indian Navy. The system comprises sonar and acoustic countermeasures to defeat a torpedo attack. The system has been subjected to about thirty performance evaluation trials under actual operational conditions.

The system has performed successfully in all the sea evaluation trials. The two production grade systems were formally inducted for active service in Indian Navy on 14 November 2015. The total cost of the project including two production grade systems is Rs 58.89 crore.


Anti-submarine warfare or ASW as it is popularly known is perhaps the most challenging and also the most fascinating form of warfare. NPOL, a constituted establishment of DRDO, occupies a unique space in oceans and ASW technology and had already developed a full platter of systems and technologies for ASW. APSOH, HUMSA, HUMSA NG and UG versions of hull mounted sonar, developed by NPOL, have been delivered to the Indian Navy (IN). Indian submarines navigate using NPOL designed submarine sonar suite USHUS and our ASW aircraft use dunking sonar and airborne processing systems.

Maareech towed array sonar based Torpedo Defence System was designed and developed by NPOL to protect the ships of IN. The survival capability of a ship is greater if the torpedo can be detected early and also at a range more than the escape range of the platform. Hence, present day maritime warfare necessitates the requirement of reliable early warning torpedo detection and countermeasure systems that can directly engage the attacking torpedo.

Maareech on-board an Indian Navy Ship

Maareech provides total defence against a torpedo attack. The main objective of the Maareech is to provide a reliable defence mechanism for all the surface ships of IN against torpedo attacks. Its core functions include automatic detection and alert of acoustic homing torpedoes (passive and active) and also acoustic decoying of the torpedo. Fully indigenous system comprises detection, classification and localization systems along with multiple types of countermeasure solutions.


The detection system developed by NPOL comprises two sonar, namely, the Hull mounted sonar and towed array sonar for passive detection. Between them they provide panoramic detection and tracking of torpedoes. Apart from that there is an intercept sensor to characterize the active homing signature of the torpedo. Acoustic decoying is effected using two types of decoys namely the towed and expendable decoy. The decoys work in multiple modes depending on the situation. The complete wet end sensors including the towed array sonar is launched and retrieved using a hydraulically operated winch system.

The onboard electronics processing system and Human Machine Interface (HMI) are combined in one single cabinet system which houses the front end electronics, signal processors and Display and control hardware. Industry standard Power PC’s and Multi SHARC FPP boards are used. The Maareech system incorporates advanced adaptive beamforming techniques for detection and tracking targets. The unique auto torpedo recognition algorithms clearly demarcate a torpedo target from non-torpedo target. Also intelligent soft kill decoy systems with multi-mode operational capability is built into towed and expendable decoy systems which helps to deter and decoy a possible attack on the mothership.

The expendable countermeasure system developed by NSTL consists of Fire Control System (FCS), Decoy Launcher (DL) and Expendable Decoy (ED). The sonar data after initial classification as a torpedo is being continuously fed to the FCS system. The target localization using Contact Motion analysis is being carried out by the FCS. Also important information regarding the target like torpedo speed, torpedo course etc. are also computed.

FCS system also generates the escape recommendations including when to launch the expendable decoy, direction of launch, own platform course and Maareech onboard IN Ship Torpedo detection and tracking in Maareech sonar display speed etc. Fire Control System (FCS) interfaced with Maareech towed and hull mounted sonar, identifies high risk adversary and generates recommendations for the Commanding officer of the ship regarding the safest escape route. Also FCS computes the time instants and number of decoys to be deployed / fired. The decoys would be deployed with the command from ASW Officer through Decoy Launcher having multiple built -in safeties. Both towed and expendable decoys can work in multiple modes namely, broad band jammer, echo repeater and transponder modes.


Maareech is capable of detecting, tracking, seducing, confusing and decoying incoming modern and vintage torpedoes. It has a maximum towing speed of 32 knots (60 km) and 10-24 knots (19 - 44 km) tactical operating speed. Production of two production grade Maareech fire control system and 40 of expendable decoys have been completed by the production agency, BEL. The features of Maareech ATDS are at par with the global torpedo defence systems. In fact, Maareech system possesses detection and decoying capabilities superior to that of global systems. Also, being totally indigenous, continuous support of DRDO and Indian industry is available for up gradation of capabilities based on new requirements arising out of tactical missions. The availability of this technology, critical know-how and support within the country empowers IN and enhances self confidence in their missions.

IN has currently projected requirement of ATDS systems for both ASW and non ASW class of ships. ATDS developed by NPOL would be required for non ASW class of ships as well. IN has projected requirement of 13 ATDS. (Adapted from DRDO News publications)

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