Mobile Platforms Provide Much-Needed Flexibility
Mobile platforms provide oceanographers the means to deploy sensors and move them through space, both horizontally and vertically. OOI uses propeller-driven Autonomous Underwater Vehicles (AUVs) and buoyancy-driven gliders to meet the requirements for oceanographic sampling.
Propeller-driven, battery-powered AUVs are somewhat like an instrumented torpedo, though optimized for longer life at slower speeds while carrying a sensor payload. Optimum speeds for AUVs used in oceanographic applications are near 1.7 m s-1, while maximum speeds of about 2.5 m s-1 may be reached.
AUVs have a high payload capacity relative to gliders, and will carry a broad suite of sensors for interdisciplinary observations. They surface to obtain position fixes using GPS and while at the surface they also enter the OOI communications network using satellite telemetry.
AUVs can run continuous missions of up to several days and are small enough to be deployed and recovered from a small boat; OOI will use this means of deployment and recovery. AUVs will operate at the Pioneer Array in conjunction with seafloor-mounted docking stations into which the AUV can swim to recharge its batteries and exchange data.
Buoyancy-driven, battery-powered gliders change their volume by pumping to or from an oil-filled bladder; when they dive or rise, the glider’s wings achieve lift allowing the glider to fly forward through the water. These mobile platforms can achieve speeds of about one tenth of those of the AUVs or ~25 to 35 cm s-1.
Gliders shift internal mass to be able to change pitch and to roll and to control their track; some gliders also use a rudder to steer. At the surface, gliders acquire position information using GPS and transmit data and receive commands via satellite. The OOI gliders will be smaller and lighter than the OOI AUVs, and multiple gliders can be deployed and recovered from a small boat.
Gliders are used throughout the Coastal Global Scale Nodes Array infrastructure. While there is some diversity in the glider missions and capabilities across the OOI, efficiencies will be realized by coordination of and commonality in the glider sensor payloads, operations and maintenance, and interfaces with OOI’s Cyberinfrastructure.