Predictions of AcousticS with Smart Experimental Networks of GlidERS (PASSENGERS)

Predictions of AcousticS with Smart Experimental Networks of GlidERS (PASSENGERS) is a research project on pairing data-assimilative ocean models with adaptive-sampling buoyancy gliders for improved acoustic predictions in strong frontal and eddy-rich environments. The PASSENGERS field campaign consisted of two research cruises near the Atlantis II Seamount in November, 2022 and May/June, 2023. More than 4,500 glider CTD profiles were taken by 7 gliders simultaneously operating in teams and more than 110 days duration of glider hydrophone data were recorded in the vicinity of acoustic source moorings. Tests on using thrusted profiling and hover thrust modes for glider operations in November yielded a maximum through the water glider speed of 0.74 m/s and implementation of these modes in May/June allowed operation of the gliders in the swift Gulf Stream currents over the seamounts. Errors in Naval Coastal Ocean Model facilitated predictions of glider paths ranged from 21-58 km per day in the Gulf Stream, but with daily course corrections the Guidance for Heterogeneous Observation SysTem (GHOST) was able to guide a glider 150 km to pass very close by an acoustic source mooring with similar performance to a human-piloted glider under the same conditions. A PASSENGERS deployed acoustic source generated mid frequency (3–10 kHz) full band LFM up and down sweeps and multi-tone frequency-shift keyed sequences that were recorded by the glider hydrophones. Subsurface acoustic ducts were routinely observed by the gliders operating south of the Gulf Stream and these may have aided reception of the acoustic source transmissions at greater distances.