Station-Keeping Underwater Gliders Using a Predictive Ocean Circulation Model and Applications to SWOT Calibration and Validation

Abstract

Instrumented ocean moorings are the gold standard for gathering in situ measurements at a fixed location in the ocean. Because they require installation by a ship and must be secured to the seafloor, moorings are expensive, logistically difficult to deploy and maintain, and are constrained to one location once installed. To circumvent these issues, previous studies have attempted to utilize autonomous underwater gliders as platforms for virtual moorings, but these attempts have yielded comparatively large station-keeping errors due to the difficulty of glider control in dynamic ocean currents. We implemented an adaptive planner using a vehicle motion model and a predictive ocean circulation model to improve station-keeping performance by incorporating anticipated currents into glider control. We demonstrate improved station-keeping performance using our planner in both simulation and in-field deployment results, and report smaller average station-keeping error than the Monterey Bay Aquarium Research Institute's M1 mooring. Finally, we utilize our simulation framework to conduct a feasibility study on using an array of autonomous gliders as virtual moorings to conduct critical calibration and validation (CalVal) for the upcoming National Aeronautics and Space Administration, Surface Water and Ocean Topography (SWOT) Mission, instead of using permanent moorings. We show that this approach carries several advantages and has potential to meet the SWOT CalVal objectives.