INS Dunagiri, Sanshodhak & Agray: Why India Commissioned 3 GRSE Warships Together

A rare triple commissioning: On 21 June 2026, three warships were formally inducted into the Indian Navy at Kolkata in one ceremony. Commissioning is the moment a warship is officially accepted into active naval service, raising the naval ensign and becoming "INS" (Indian Naval Ship). This was the first occasion on which a single Indian shipyard — GRSE — delivered three major surface warships for commissioning on the same day.

Three ships, three different missions: The significance lies not just in numbers but in diversity. The three platforms add three distinct capabilities at once — a frigate built to fight far out at sea, a survey vessel built to map the sea, and a small craft built to hunt submarines close to the coast. Commissioning such different technologies together signals the maturing of India's naval shipbuilding ecosystem.

A symbolic date: The event coincided with the International Day of Yoga and World Hydrography Day, observed globally on 21 June. The induction of India's newest hydrographic survey vessel, INS Sanshodhak, on World Hydrography Day was highlighted as a meaningful coincidence.

Destroyers and frigates: Warships are broadly classified by size, role and firepower. A destroyer is a large, heavily armed surface combatant for fleet air-defence and strike. A frigate is smaller than a destroyer but still large enough to operate far from the coast (a "blue-water" platform), used for multi-mission roles including anti-air, anti-surface and anti-submarine warfare. INS Dunagiri is a frigate.

Corvettes and shallow-water craft: A corvette is smaller than a frigate, suited to coastal and littoral (near-shore) operations. INS Agray is an Anti-Submarine Warfare Shallow Water Craft (ASW SWC), a small, specialised submarine-hunter for coastal waters.

Survey/auxiliary vessels: Not all naval ships are combatants. A survey vessel is a non-combat auxiliary whose job is to measure and map the sea. INS Sanshodhak is a Survey Vessel (Large), or SVL. Understanding this hierarchy — destroyer > frigate > corvette, plus support ships — is useful for the exam.

The programme: Project 17A (P-17A), the Nilgiri-class, is a programme to build seven advanced stealth guided-missile frigates as a successor to the Project 17 (Shivalik-class) frigates. It was cleared by the Defence Acquisition Council in 2009, approved by the Cabinet Committee on Security, and contracted in 2015. The ships are designed by the Warship Design Bureau and built under a 4:3 split between Mazagon Dock Shipbuilders (MDL), Mumbai, and GRSE, Kolkata. The seven ships are named after Indian hill ranges: Nilgiri, Udaygiri, Himgiri, Taragiri, Mahendragiri, Dunagiri and Vindhyagiri.

What "stealth" means here: Stealth does not mean invisibility; it means a reduced signature. P-17A frigates have a low Radar Cross-Section (RCS) achieved through clean hull shaping and radar-absorbent materials, plus a reduced infrared (heat) signature, making them harder to detect and target. INS Dunagiri is described as built to "act like a ghost on the water".

Firepower and sensors: INS Dunagiri carries BrahMos supersonic surface-to-surface cruise missiles (anti-ship and land-attack), the Barak-8 / Medium Range Surface-to-Air Missile (MRSAM) via a Vertical Launch System, a main gun, and anti-submarine torpedoes and rockets. Its sensor suite includes the MFSTAR (Multi-Function Surveillance, Track and Guidance Radar), the HUMSA-NG sonar and the indigenous Shakti Electronic Warfare suite. It can operate two multi-role helicopters.

Indigenous engineering: The hull uses indigenous DMR-249A warship-grade steel (from SAIL). Propulsion is a Combined Diesel or Gas (CODOG) arrangement driving Controllable Pitch Propellers, managed by an Integrated Platform Management System. INS Dunagiri revives the name of an earlier Leander-class frigate that served from 1977 to 2010.

Hydrography defined: Hydrography is the science of measuring and describing the physical features of seas, oceans and coastal areas — water depth, the shape and nature of the seabed, tides, currents and underwater hazards — and presenting them as nautical charts.

Why it matters: Warships and submarines do not move through an empty ocean. They move through waters shaped by depth, seabed features, currents, reefs, channels, ports and coastal clutter. Accurate charts let ships navigate safely, help submarines plan routes, allow ports to update navigational data, and support operations. Hydrographic data also serves civilian needs — safe shipping, disaster relief, ocean research and coastal development — making it central to India's blue economy.

What INS Sanshodhak does: Its name means "Researcher". It conducts full-scale coastal and deep-water hydrographic surveys of port and harbour approaches, determines navigational channels and routes, and collects oceanographic and geophysical data for both defence and civil use. It carries an Autonomous Underwater Vehicle (AUV), a Remotely Operated Vehicle (ROV), a Digital Side Scan Sonar and a Data Acquisition and Processing System. In a secondary role it can support search-and-rescue and act as a hospital ship during disaster relief (HADR).

The bigger picture: It is the fourth and final ship of the Sandhayak-class Survey Vessels (Large), replacing older 1980s survey ships and strengthening India's hydrographic capability. India's hydrographic charts also support smaller Indian Ocean states, adding a diplomatic dimension.

The challenge of the littorals: Anti-Submarine Warfare (ASW) is the detection, tracking and destruction of enemy submarines. Coastal waters are difficult places to find submarines — they are noisy, busy and cluttered. Fishing boats, merchant ships, an uneven seabed and constant coastal activity make submarine detection harder than in the open ocean. Dedicated shallow-water craft are needed to guard ports, naval bases and key sea approaches.

INS Agray's role: INS Agray belongs to the Arnala-class Anti-Submarine Warfare Shallow Water Craft (ASW SWC), designed and built by GRSE specifically to detect and attack submarines in shallow, near-shore (littoral) waters. Its missions include subsurface surveillance, search-and-attack operations and coordinated ASW with naval aircraft, with secondary roles in mine-laying and search-and-rescue.

Weapons and sensors: It carries lightweight torpedoes, an indigenous RBU-6000 anti-submarine rocket launcher, a GRSE-developed 30 mm naval gun, and anti-submarine mine rails. For detection it uses a hull-mounted sonar (the indigenous Abhay system) and a Low-Frequency Variable Depth Sonar. It has a reduced radar cross-section and low acoustic and infrared signatures.

A propulsion first: At about 77 metres, the Arnala-class craft are among the largest Indian naval warships propelled by waterjets (a diesel–waterjet combination), which allow quick sprints and better manoeuvrability in shallow water. They replace the ageing, Soviet-origin Abhay-class corvettes. INS Agray is part of a wider 16-ship ASW SWC programme — eight Arnala-class by GRSE and eight Mahe-class by Cochin Shipyard (CSL).

The shift: For decades India was among the world's largest arms importers. Since around 2014, under Atmanirbhar Bharat and Make in India, the Navy has emphasised building rather than buying — described as the move from a "Buyer's Navy" to a "Builder's Navy". India is now the only non-P5 country able to build both aircraft carriers and nuclear-powered submarines.

The Float–Move–Fight framework: Indigenisation is measured across three categories — "Float" (hull and structure), "Move" (engines and propulsion) and "Fight" (sensors and weapons). India has achieved very high indigenisation in "Float", strong levels in "Move", but lower in "Fight", where advanced engines, sensors and weapons still require imports — the key remaining gap.

Policy scaffolding: Indigenisation is driven by the Defence Acquisition Procedure (DAP) 2020 with its "Buy Indian-IDDM" priority, Positive Indigenisation Lists, the iDEX innovation platform, and the Indian Naval Indigenisation Plan (INIP) 2015–2030. Warship-grade DMR-249A steel, jointly developed by the Navy, DRDO and SAIL, made India self-reliant in shipbuilding steel.

Why GRSE matters: Founded in 1960, GRSE is the only Indian yard to have delivered over 100 warships, the first to build a fleet replenishment tanker, and the first to export an Indian-built warship. Its role in this triple commissioning reflects the depth of India's defence-industrial base.

A contested ocean: The Indian Ocean Region (IOR) carries a large share of global trade and energy flows and is increasingly contested, with the Chinese PLA Navy expanding its footprint. A capable navy is essential to protect sea lanes, India's Exclusive Economic Zone, and its maritime interests.

Capability in layers: The triple commissioning reflects a strategy of building capability in layers — big frigates for distant blue-water operations, survey ships to understand the sea, and small submarine-hunters to guard coastal waters. Each ship plugs a different gap.

Doctrine: India's maritime outreach is guided by the vision of SAGAR (Security and Growth for All in the Region), articulated in 2015 and expanded in 2025 into MAHASAGAR (Mutual and Holistic Advancement for Security and Growth Across Regions), alongside Maritime Vision 2030. Indigenous warship-building underpins this by ensuring operational autonomy and supply-chain security.

Close the "Fight" gap: India's strongest indigenisation is in hull and structure ("Float"); sustained investment in indigenous engines, sonars, sensors and weapons ("Move" and "Fight") is the next frontier, requiring higher defence R&D spending.

Sustain delivery tempo without cost or quality slippage: Running multiple ship programmes simultaneously risks cost overruns and schedule delays; strengthening shipyard capacity, supply chains and project management is essential.

Deepen private-sector and MSME participation: Moving private firms from sub-system suppliers towards prime integrators, and supporting the 200-plus MSMEs in such programmes, will broaden the defence-industrial base.

Leverage hydrographic and survey strengths diplomatically: Survey vessels and charting support can deepen India's role as a net security and capacity provider in the Indian Ocean under SAGAR/MAHASAGAR.

Maintain ASW and littoral focus: As submarine activity in the IOR grows, completing the ASW SWC and survey programmes and accelerating next-generation projects will keep India's coastal and blue-water layers credible.