SOURCE: AFI
In a strategic move to bolster maritime security in the Indian Ocean Region (IOR), the Indian Navy, in collaboration with the Defence Research and Development Organisation (DRDO) and private sector companies, is planning to develop advanced underwater sensors to detect submarine movements in areas conducive to such operations.
This initiative, aims to address the growing presence of foreign submarines, particularly from China, in the IOR—a region critical to India’s geopolitical and economic interests. The development of these sensors is part of a broader effort to enhance India’s underwater domain awareness (UDA) and counter the increasing subsurface threats posed by regional adversaries.
The IOR has emerged as a contested maritime space, with India facing significant challenges from the People’s Liberation Army Navy (PLAN), which has been expanding its submarine operations in the region. Recent activities, such as the month-long survey of the Ninety East Ridge by China’s “silent” research vessel Dong Fang Hong 3 in March 2025, have heightened concerns about China’s ability to map underwater environments for submarine operations. The Ninety East Ridge, a linear intraplate rise ideal for submarine navigation, underscores the strategic importance of monitoring such areas to prevent undetected incursions by foreign submarines.
China’s growing fleet of over 60 submarines, including six Jin-class nuclear-powered ballistic missile submarines (SSBNs), has been a focal point of concern for India. The PLAN’s regular forays into the IOR, often under the guise of scientific research, have been linked to intelligence-gathering missions, as evidenced by the presence of Chinese vessels during India’s K-4 missile test in January 2025. Moreover, Pakistan’s acquisition of eight Yuan-class submarines with air-independent propulsion (AIP) systems from China has further complicated India’s maritime security landscape, creating a two-front challenge in the IOR.
India’s current submarine fleet, consisting of 13 conventional diesel-electric submarines (nine Sindhughosh-class and four Shishumar-class), lacks the numerical and technological edge to counter these threats effectively. The Indian Navy’s ongoing Project 75I to build six AIP-equipped submarines has faced delays, and the absence of indigenous AIP systems in the first batch of these submarines has raised concerns about their operational endurance. In this context, the development of underwater sensors to detect submarine movements is a critical step toward enhancing India’s anti-submarine warfare (ASW) capabilities and maintaining its pre-eminence in the IOR.
The Indian Navy has long recognized the need for robust UDA to monitor the vast expanse of the IOR, which includes key chokepoints like the Malacca Strait and the Sunda Strait. The collaboration with DRDO and private sector companies builds on previous efforts to develop indigenous underwater technologies, such as the Naval Physical and Oceanographic Laboratory’s (NPOL) sonar systems. NPOL, based in Kochi, has a proven track record of delivering underwater sensors for the Indian Navy, including the Abhay sonar for shallow water crafts, the HUMSA-UG hull-mounted sonar, and the AIDSS distress alert sonar system for Sindhughosh-class submarines, as reported by The Hindu in 2016.
The new initiative focuses on creating a network of underwater sensors capable of detecting submarine movements in areas where such operations are conducive, such as the Ninety East Ridge, the Andaman and Nicobar Islands, and the Bay of Bengal. These sensors will likely include advanced hydroacoustic systems, similar to those used by the United States and Japan in their “Fish Hook Undersea Defense Line” in the Pacific, which stretches from Japan to Southeast Asia. The Indian Navy aims to deploy these sensors at strategic locations, such as the northern and southern tips of the Andaman and Nicobar Islands, to provide early warning of Chinese submarine presence in the IOR.
The underwater sensors under development are expected to leverage cutting-edge technologies, including passive and active sonar systems, magnetic anomaly detectors (MAD), and superconducting quantum interference devices (SQUIDs). Passive sonar, which detects noise emitted by submarines without emitting signals, will be crucial for stealthy surveillance, while active sonar can provide precise ranging in high-threat scenarios.
DRDO’s experience with the Submersible Platform for Acoustic Characterisation & Evaluation (SPACE) facility in Kochi, launched in 2022, will be instrumental in testing and calibrating these sensors. The SPACE facility, a state-of-the-art platform capable of being lowered to depths of 100 meters, allows for the evaluation of sonar systems in controlled environments, ensuring their reliability before deployment on naval platforms. Additionally, DRDO’s Ocean Data Centre at NPOL can support the project by providing a centralized platform for oceanographic and acoustic data, aiding in the design and optimization of the sensors.
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