Underwater gliders are autonomous vehicles that profile vertically by controlling buoyancy and move horizontally on wings. Russ Davis, Jeff Sherman and the Instrument Development Group at Scripps Institution of Oceanography have developed the glider Spray. Spray is 2 m long and weighs 50 kg. It communicates to shore using Iridium, and navigates with GPS. Spray steers by changing its center of mass through the movement of internal heavy battery packs. Spray carries sensors to measure a number of variables, including pressure, temperature, salinity, optical properties, and velocity.

In typical use, Spray cycles from the surface to 1000 m, traveling 6 km in the horizontal in 6 hours. Spray’s horizontal velocity is thus about 0.25 m/s, and its vertical velocity is roughly 0.1 m/s. GPS and Iridium antennas are in Spray’s wings, so when Spray is on the surface it rolls 90° to navigate and communicate. During communication, Spray sends data to shore, and shore-based pilots can change mission parameters such as waypoints and dive depth. Typical deployment duration is 3-5 months, depending on sensor suite, stratification, dive depth, and profiling speed.