Sensor networks for cabled ocean observatories

An infrastructure for global, regional, and coastal sub-sea observatories is being planned to support individual and networked sensors. The main emphasis has been to provide basic power and communications capability at "primary" nodes; less has been given to the sensor network infrastructure that extends the capability of the observatory into the full three-dimensional volume of interest. Secondary cabled and junction boxes are needed to extend the horizontal reach by tens to hundreds of kilometers from the primary nodes; moorings up into the water column and boreholes into the sediments and crust are necessary to extend the vertical reach. The support infrastructure must include navigation and communications systems, mobile platforms such as free-swimming autonomous undersea vehicles, and bottom rovers that carry sensors and provide data and energy "tanker" service. The requirements for these various network elements and possible solutions are discussed, with an emphasis on the design of a specific mooring for the ALOHA Observatory north of Oahu. This subsurface mooring supports a full-water-column moored profiler with a docking station that transfers power and data, enabling adaptive sampling. The subsurface float at 200 m provides a ROV-serviceable platform for near surface instrumentation, such as an upward looking acoustic Doppler current profiler and a winched sensor system.