Hardware for China's neutrino telescope passes a deep-sea test

Shanghai Jiao Tong University (SJTU) reported on Sunday that Chinese researchers had finished testing the engineering and precision instruments of the Tropical Deep-sea Neutrino Telescope (TRIDENT), a potent underwater telescope constructed at a depth of 3,500 meters.

The TRIDENT project, also known as the Hailing (ocean bell) project in Chinese, is a deep-sea neutrino detection project with the goal of constructing the largest neutrino telescope in the world in the South China Sea. According to a statement from SJTU, it aims to investigate cutting-edge scientific issues like the origin of cosmic rays and extreme astrophysical phenomena by detecting high-energy neutrino signals. It also promotes interdisciplinary research in fields like particle physics, astronomy, and ocean engineering.

Ten neutrino detection strings, each roughly 700 meters tall, will be deployed in phase I of the project at a depth of 3,500 meters to create a compact array. According to SJTU, the sea testing concentrated on important technology advancements for the project’s Phase I construction, such as the deep-sea wet-mate connectors, underwater acoustic location, and the subsea precision instrument deployer with elastic release (SPIDER) system.

In order to confirm impact resistance and deep-sea precision positioning capacity, the SPIDER system successfully completed a seabed landing test at 3,500 meters as well as a coordinated movement test with a dynamically positioned vessel.

Xu Donglian, the chief scientist of the telescope from the Tsung-Dao Lee Institute under SJTU, stated that TRIDENT creatively observes the universe by “looking down” rather than “looking up” at the sky, using the Earth as a shield when capturing high-energy neutrinos penetrating from the opposite side of the globe, and achieving detections without a dead angle through Earth rotation, despite the fact that neutrinos rarely interact with matter and can escape from dense celestial environments, which are difficult to detect, according to Xinhua News Agency.

During the sea trial, the prototype model of TRIDENT’s hybrid Digital Optical Module design—the telescope’s central component—captured faint neutrino signals and attained single-photon-level precision in incredibly weak conditions.

In the meantime, five residential systems of the deep-sea wet-mate connector—a crucial component connecting subsurface buoys with seabed junction boxes in Phase I of the project—went through many 3,500-meter underwater mating tests conducted by the project team.

The neutrino environmental mooring and neutrino mooring deployed in April 2025 were also successfully recovered by the scientists during this journey. Along with equipment operating records, these moorings offer full-cycle meteorological, oceanographic, and hydrological environmental information. The majority of sensors produced long-term continuous data to aid in the selection of deep-sea neutrino observatory sites with no biofouling.

Additionally, the scientists’ large-volume filtration experiments and in-situ sampling have produced important references for deep-sea neutrino signal studies as well as biodiversity data on the abyssal plain.

IMAGE: The subsea precision instrument deployer, equipped with an elastic releasing system, is prepared for deployment on the ship’s aft deck. Photo: Screenshot from website