KOCHI, — The Naval Physical and Oceanographic Laboratory (NPOL), a research laboratory of the Defence Research and Development Organisation (DRDO) in Kochi, has issued a Request for Proposal (RFP) for the development of Version 2 Side Scan Sonar (SSS) and Multi-Beam Echo-Sounder (MBE) transducer arrays for two Autonomous Underwater Vehicles (AUVs).
The procurement aims to equip the underwater vehicles with acoustic sensors for high-resolution seabed imaging, depth measurement and maritime surveys. The RFP specifies four 1.8-metre Side Scan Sonar arrays for port and starboard mounting, along with two complete sets of Multi-Beam Echo-Sounder arrays, each comprising transmitter and receiver elements.
Technical Requirements for Side Scan Sonar
The SSS arrays will operate in the 450–500 kHz frequency range, with a bandwidth greater than 50 kHz. Each array must include 40 receiver (Rx) modules and three transmitter (Tx) modules.
The specified receive beamwidth is 0.1° × 45°, with a source level of at least 203 dB and receive sensitivity of –200 dB or better. The system must also include a 38 dB preamplifier.
Side-scan sonar produces acoustic images of the seabed by transmitting sound pulses to either side of a moving platform. The resulting images can help identify underwater objects, including mines, wrecks and debris.
Multi-Beam Echo-Sounder Specifications
The MBE arrays will operate in the 625–675 kHz frequency range, with a bandwidth of 50 kHz. The specified configuration includes 96 receiver modules and three transmitter modules.
The system must achieve a source level of at least 185 dB and receive sensitivity of –208 dB or better.
Unlike side-scan sonar, which primarily produces seabed images, a multi-beam echo-sounder measures depth across multiple beams to generate detailed underwater topographical maps. The two systems will provide complementary imaging and survey capabilities for the AUVs.
Deep-Water and Environmental Testing
NPOL requires both sonar systems to operate at depths of 300 metres or more. Their structural design must withstand a baseline hydrostatic pressure of 30 bar, with pressure testing specified between 35 and 45 bar.
The equipment must also undergo thermal endurance tests and withstand vibration levels of up to 6 Grms to meet the specified environmental and mechanical requirements.
Supporting India’s Underwater Capabilities
NPOL, based in Thrikkakara, Kochi, works on sonar systems, underwater surveillance technologies and oceanographic research in support of the Indian Navy.
The new procurement aligns with India’s efforts to expand the use of uncrewed underwater systems for maritime surveys and mine-countermeasure missions. In November 2025, the Naval Science and Technological Laboratory (NSTL) in Visakhapatnam, working with NPOL and other DRDO laboratories, completed development of a new generation of man-portable AUV swarms equipped with side-scan sonar and cameras. The systems underwent field trials and were prepared for production.
The latest RFP seeks transducer arrays that meet the specified acoustic performance and environmental requirements for integration into two designated AUVs. Further information on delivery timelines, bidder eligibility and evaluation criteria is available in the official tender documents.
——— End of Article ———