Deepglider Reliability Development

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This project will carry out further development and testing to bring the advanced prototype for a full ocean depth capable glider to the stage that it can be used for scientific investigation. Deepgliders are designed to dive to as deep as 6 km and return to the sea surface about 250 times in a single mission lasting as long as 18 months and traveling as far as 10,000 km through the ocean. They sample temperature, salinity, and dissolved oxygen along sawtooth paths through the ocean and communicate them to shore via satellite telemetry. Two-way communication allows commands to be transmitted so that autonomous behavior can be controlled remotely from a pilot anywhere with an internet connection. The projected operational cost of each slanting full depth profile is ~$120, almost two orders of magnitude less than what a deep ocean hydrographic cast costs (although deep casts generally measure many more variables). Deepgliders offer sampling persistence and frequency that is unmatched by ships. Their mobility and remote control enables spatial description of the ocean's internal structure that would require an underwater forest of moored sensors to match. Their economy can be exploited to observe the deep ocean far more intensively and extensively than is possible with conventional methods so as to answer fundamental questions about ocean circulation, the role of the ocean in climate, boundary current systems, and omnipresent mesoscale eddies.Three Deepgliders capable of diving to 6 km depth have been constructed to date, two of which have been lost in a total of 5 trial deployments in the tropical Atlantic in the past year. One was adrift at the sea surface with communication difficulties when lost in a mission that had sampled only the upper ocean, while effects of high pressure may not be ruled out in the other loss. Deepglider has reached 5920 m depth, executed a 275 km section to 5250 m depth, used energy at a rate that implies 18 month missions are feasible, and measured temperature and salinity with resolution and stability comparable to what is attained with CTD casts. The purpose of this project is to improve the reliability of Deepglider so that it can achieve design mission endurance and range goals, evaluate the stability and accuracy of its measurements, and develop it into a credible tool for oceanographic research. Several new Deepgliders are to be constructed and used in an extensive program of both laboratory and field tests. Results from a staggered sequence of tests on the currently available Deepglider and the first of the new units will be used to modify the design of the subsequent units. Laboratory tests will include intensive pressure cycle tests of hull integrity and buoyancy engine performance. Field tests will take place at a deep ocean time series site for logistic convenience and the availability of regular high quality shipboard and moored measurements for comparison, most likely the Hawaii Ocean Time-series Study (HOTS) site or the Bermuda Atlantic Time-series Study (BATS) site.Intellectual Merit: This project will bring to readiness a technique that will extend autonomous underwater glider depth range to the water column entirety in nearly the entire ice-free open deep ocean, endurance to more than one year, and horizontal range to 10,000 km. These improvements by factors of 2-6 over present technology are projected to accompany reductions in glider usage cost and only a modest (~25%) increase in glider fabrication cost.Broader Impact: The transition of Deepglider from advanced prototype to reliable oceanographic tool will enable extensive, relatively frequent sampling of the deep ocean?s temperature, salinity, oxygen, and current structure. Affordable means to sample the water column will advance knowledge of ocean circulation and the ocean?s role in climate. The technology will invite the development and addition of other sensors to Deepglider as a versatile platform for ocean observation. It will also lead to commercialization and widespread use of such vehicles.