Two-Year Optical Site Characterization for the Pacific Ocean Neutrino Experiment P-ONE in the Cascadia Basin

The STRings for Absorption length in Water (STRAW) experiment is the first in a series of pathfinder missions for the Pacific Ocean Neutrino Experiment (P-ONE), a future large-scale neutrino telescope in the north-eastern Pacific Ocean. STRAW consists of two 150 m long mooring lines instrumented with optical emitters and detectors. The experiment is designed to measure the attenuation length of the water and perform a long-term assessment of the optical background at the future P-ONE site. After two years of continuous operation, measurements from STRAW show an optical attenuation length of about 28 metres at 450 nm. Additionally, the data allows a study of the ambient undersea background. The overall optical environment reported here is comparable to other deep-water neutrino telescopes and qualifies the site for the deployment of P-ONE.