Development and Evaluation of the New RBRlegato3 CTD on Glider Platforms

Building on long-term development for the Argo program, the RBRlegato³ CTD has been developed to improve measurements, enable longer missions, and reduce calibration down-time for ocean gliders. TheRBRlegato³ provides CTD measurements calibrated to WOCE specifications for accuracy and stability. TheRBRlegato³ measures conductivity using a rugged inductive cell that is not affected by surface contaminants or freezing conditions. The CFD-optimised, low aspect ratio conductivity cell is self-flushing and does not require a pump. Using only 72mW (6mA at 12V) when sampling at 2Hz or faster, and 18mJ/sample at 1Hz or slower, the power requirement is about 75% lower than traditional pumped CTD sensors. Totally silent operation is optimized for passive acoustic listening and turbulence measurements. The RBRlegato³ is designed to fit into a standard 2″ x 7″ sensor bay, with both wet-bay and dry-bay models, and is rated to 1000m. The presentation will report on RBR's collaboration with glider manufacturers and scientists including integration of the new CTD, development of dry-bay and wet-bay mechanical solutions, and performance in strongly stratified environments. RBRlegato³ CTD data is evaluated using QARTOD tests, nearby CTD profiles, and other glider CTDs. We focus specifically on sensor accuracy, but also analyze upcast/downcast pairs for evidence of dynamic performance in strongly stratified conditions.