China's repeated deployment of "research" vessels in the Indian Ocean coincides with India's strategic missile tests, particularly concerning the development and testing of India's sea-based nuclear deterrent. Currently, four notable Chinese ships—Lan Hai 101, Lan Hai 201, Shen Hai Yi Hao, and Shi Yan 6—are active or en route in this region.

These vessels conduct activities like oceanographic surveys, seabed mapping, and geophysical research but are widely understood to serve dual-use purposes, including naval reconnaissance and intelligence gathering on India's missile tests and submarine operations.

Lan Hai 101, an aquaculture research ship fitted for extensive oceanographic surveys, is heading toward Sri Lanka's Galle port—a frequent stop during Indian missile tests. Shi Yan 6 is moving toward Mauritius after operations across the Indo-Pacific, while Shen Hai Yi Hao, equipped with a deep-sea manned submersible, is conducting survey work near Southeast Asia and entering the wider Indian Ocean basin.

Lan Hai 201 has been active near the strategic Diego Garcia base, engaged in seabed and hydrological mapping. India has previously delayed or cancelled missile tests due to Chinese vessels loitering near danger zones, highlighting the sensitivity of their presence.

The main Indian strategic concern surrounds the testing of longer-range submarine-launched ballistic missiles (SLBMs), particularly the K-4 missile, which significantly extends India's sea-based nuclear reach from the currently deployed K-15 Sagarika missile.

With its roughly 3,500 km range, the K-4 enables Indian SSBNs to maintain a secure bastion in the Bay of Bengal while still threatening key Chinese targets. This advancement enhances India’s second-strike nuclear capability, a critical component of credible deterrence, thereby raising Beijing’s strategic interest in monitoring these tests closely.

China's wider objective mixes intelligence gathering for missile telemetry with comprehensive oceanographic data collection to improve undersea warfare capabilities. Acoustic conditions, seabed composition, thermoclines, and salinity impact submarine stealth and detection.

Chinese survey vessels in the Indian Ocean Region have been strategically positioning themselves along anticipated trajectories of Indian missile tests to gather critical intelligence. Their objectives extend beyond missile tracking to collecting detailed oceanographic and acoustic data essential for modern submarine warfare, which relies heavily on how sound travels under different sea conditions. This intelligence aids China in enhancing its naval stealth, submarine navigation, and undersea warfare capabilities against India.

These vessels, while ostensibly conducting scientific and oceanographic surveys, monitor Indian missile trajectories, record acoustic signatures, and analyse missile debris patterns during tests conducted near the eastern seaboard, particularly around the Bay of Bengal and near the Integrated Test Range on Abdul Kalam Island.

Such data collection allows China to refine its ability to detect and evade Indian submarine activities, which form a crucial part of India's strategic deterrent, including submarine-launched ballistic missile (SLBM) capabilities like the K-4 missile.

Chinese survey ships like Shi Yan-6 and Xiang Yang Hong 03 are equipped with sophisticated sensors and radars to conduct underwater mapping, sonar profiling, and track missile firings. India's postponement of missile tests has been linked to the presence of these vessels, which relay gathered intelligence back to Chinese command centres for enhanced strategic naval operations. The continuous oceanographic mapping also supports Chinese submarine deployment strategies, including navigating choke-points and counteracting anti-submarine warfare measures in the Indian Ocean.

Through the deployment of advanced sensors, autonomous underwater vehicles, and deep-sea submersibles, Chinese vessels create detailed oceanic profiles vital for stealth submarine deployment and detection of adversary SSBNs, including India’s.

Such intelligence supports China’s strategic advantage in the Indian Ocean, where it seeks to counter India’s growing naval and nuclear capabilities.

Overall, the recurring presence of Chinese research ships during major Indian missile tests and their extensive oceanographic missions exemplify Beijing's persistent efforts to gain strategic dominance under the guise of scientific research.

This creates a significant challenge for India’s pursuit of a credible, secure sea-based nuclear deterrent in a contested Indian Ocean region where undersea situational awareness is crucial for future deterrence stability.​

IDN (With Agency Inputs)