A fourth Chinese survey ship has entered the Indian Ocean ahead of a likely major Indian ballistic missile test.

The Da Yang Hao, which began its active life in July 2019, is thought to be one of the most advanced vessels in China’s survey fleet. It has been described as a ‘floating laboratory’.

The Da Yang Hao joins three other Chinese survey ships which have taken up strategic positions in the Indian Ocean and the Bay of Bengal. The Xiang Yang Hong 03 has been conducting oceanographic surveys for several weeks now and has docked twice at the Maldives capital Male.

Another survey vessel, the Xiang Yang Hong 01, has been prowling about the Bay of Bengal for several days now and it arrived just before an Indian missile test. At one point, the ship was just 250 nautical miles from Vishakapatnam.

One of the two most recent arrivals in the Indian Ocean is the Yuan Wang 03, which is unambiguously described by the China’s Global Times as a “space tracking ship” that monitors missile launches. This vessel was spotted entering the Sunda Strait an entry point from the Java Sea into the Indian Ocean.

The Da Yang Hao appears to have also strategically taken up position in the Indian Ocean in the last few days. The maritime website Maritime Optima said on Thursday night, “We last observed the vessel in the Indian Ocean less than 1 hour ago.”

India has announced a ‘NOTAM’ (notice to airmen) for April 3 or April 4 that stretches for about 1,600km across the length of the Bay of Bengal. There’s speculation that India aims to test the Agni Prime, a nuclear-capable ballistic missile. The Indian navy is closely monitoring the activities of all four vessels.

The ultra-hitech Da Yang Hao has been described by analysts as a “floating laboratory”. It is said to have 400sq metres of laboratories all focused on marine geology, marine ecology and, significantly, the atmosphere.

In 2021, the Da Yang Hao caused considerable anger when it moved into the exclusive economic zone of Palau, a small island nation near the Philippines. The ship ignored increasingly strong demands for it to move out of Palau’s EEZ. Palau does not have its own navy.

China is now thought to have a fleet of about 64 research and survey ships. This is one of the largest such fleets in the world. The Chinese are also, in keeping with the larger global role they see for themselves, moving to new marine geographies and regions like the Indian Ocean.

These Chinese survey vessels have been making increasingly frequent trips to the Indian Ocean. In December 2022 India had cancelled a missile test when it discovered a Chinese tracking ship was about to enter the region.

The Chinese insist the vessels are only for research and part of its drive to create a “strong maritime country” India calls the boats “spy ships” that are seeking to collect sensitive information.