P-ONE: the neutrino telescope being plugged into the bottom of the Pacific

Most neutrino telescopes are defined by the heroic effort it takes to get power and data to them. IceCube melts holes two kilometres down in Antarctic ice. KM3NeT and Baikal-GVD send ships and submersibles out to anchor and connect each string by hand. The Pacific Ocean Neutrino Experiment, or P-ONE, is being designed around a different idea: build the detector where the infrastructure already exists. About 2,600 metres beneath the surface off the coast of Vancouver Island, a fibre-optic cable has been carrying power and data to the seafloor for more than a decade. P-ONE wants to plug in.

A telescope that comes with wiring

The cable belongs to Ocean Networks Canada, which operates a cabled seafloor observatory called NEPTUNE in the Cascadia Basin. Originally built for oceanography — monitoring earthquakes, currents, marine life, and the chemistry of the deep ocean — NEPTUNE provides something neutrino physicists usually have to fight for: a permanent, high-bandwidth connection between the abyss and the shore, with real power delivered continuously rather than scavenged from batteries.

That changes the engineering problem. A neutrino telescope is essentially a three-dimensional grid of light sensors watching a huge, transparent volume of natural material. When a neutrino interacts in or near the detector, it produces charged particles that race through the water faster than light travels in that medium, emitting a faint cone of blue Cherenkov radiation. Reconstructing the direction and energy of that flash requires thousands of sensors and a steady stream of timing data back to land. With an existing cabled backbone, P-ONE can focus its budget on the optical modules themselves rather than on the costly business of powering and reading them out.

Reading the water first

Before committing to a kilometre-scale array, the collaboration had to answer a basic question: is the deep Pacific clear enough? Cherenkov detection depends on how far blue light can travel before being absorbed or scattered, and every site has its own optical fingerprint. To measure it, the team deployed two pathfinder missions — STRAW in 2018 and STRAW-b in 2020 — short strings of light sources and sensors lowered into the Cascadia Basin.

The results were encouraging: long absorption lengths, manageable scattering, and a bioluminescence background that, while present, was tolerable. Seawater detectors live with two natural nuisances that Antarctic ice does not have — radioactive potassium-40 dissolved in the salt, and living organisms that emit their own light. Characterising both was the whole point of the pathfinder phase, and the data fed directly into the geometry and triggering plans for the full instrument.

Seventy strings in clusters

The current design calls for roughly 70 vertical strings, each about a kilometre tall and held upright by buoyancy, grouped into clusters of ten. Each cluster connects to the cabled network through its own node, so the array can grow one segment at a time rather than waiting for a single monolithic build. The optical modules borrow an approach proven by KM3NeT: instead of one large photomultiplier per sphere, each module packs several smaller tubes, which improves the ability to tell a real signal from random background and gives some directional information from a single hit.

P-ONE’s location matters as much as its size. Sitting in the Northern Hemisphere, it looks through the Earth to watch the southern sky — including the centre of our galaxy — which is the region IceCube sees best from the South Pole only with difficulty. A telescope in the North Pacific, another in the Mediterranean, one in Lake Baikal, and IceCube at the pole together cover the entire sky with overlapping fields of view. Researchers have begun sketching a combined analysis framework that would treat these separate instruments as a single planetary observatory, pooling their data to localise transient cosmic sources faster than any one detector could alone.

Where it fits

P-ONE is still in its construction-and-prototyping phase rather than full operation, with a first instrumented line intended to demonstrate the cabled design before the clusters are rolled out through the late 2020s. If it succeeds, it will join a small but growing family of experiments — alongside Baikal-GVD and the planned IceCube-Gen2 expansion — that are scaling high-energy neutrino astrophysics from the proof-of-concept era into routine astronomy.

The deeper lesson of P-ONE may be strategic rather than technical. The first generation of neutrino telescopes treated their environments as obstacles to be conquered. P-ONE treats the ocean, and the cable already lying on its floor, as an asset to be borrowed. For a field that has spent decades building its own infrastructure from scratch in the most inhospitable places on Earth, that is a quietly radical change of approach.

Neutrino Times Editorial Team. (2026, May 25). P-ONE: the neutrino telescope being plugged into the bottom of the Pacific. Neutrino Times. https://neutrino-times.com/articles/p-one-pacific-ocean-neutrino-experiment/

Neutrino Times Editorial Team. "P-ONE: the neutrino telescope being plugged into the bottom of the Pacific." Neutrino Times, May 25, 2026. https://neutrino-times.com/articles/p-one-pacific-ocean-neutrino-experiment/.

Neutrino Times Editorial Team. "P-ONE: the neutrino telescope being plugged into the bottom of the Pacific." Neutrino Times, 25 May. 2026, https://neutrino-times.com/articles/p-one-pacific-ocean-neutrino-experiment/.

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  author       = {Neutrino Times Editorial Team},
  title        = {P-ONE: the neutrino telescope being plugged into the bottom of the Pacific},
  howpublished = {Neutrino Times},
  year         = {2026},
  month        = {may},
  url          = {https://neutrino-times.com/articles/p-one-pacific-ocean-neutrino-experiment/},
  note         = {Accessed: 2026-05-25}
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