A team from the Applied Physics Laboratory of the University of Washington (APL-UW) conducted underwater sound propagation exercises from 5 to 29 May 2010 aboard the R/V Roger Revelle in the Philippine Sea. This research cruise was part of a larger multi-cruise, multi-institution effort, the PhilSea10 Experiment, sponsored by the Office of Naval Research, to investigate the deterministic and stochastic properties of long-range deep ocean sound propagation in a region of energetic oceanographic processes. The primary objective of the APL-UW cruise was to transmit acoustic signals from electro-acoustic transducers suspended from the R/V Roger Revelle to an autonomous distributed vertical line array (DVLA) deployed in March by a team from the Scripps Institution of Oceanography (SIO.) The DVLA will be recovered in March 2011.

Two transmission events took place from a location designated SS500, approximately 509 km to the southeast of the DVLA: a 54-hr event using the HX554 transducer at 1000 m depth, and a 55-hr event using the MP200/TR1446 "multiport" transducer at 1000 m depth. A third event took place towing the HX554 at a depth of 150 m at roughly 1–2 kt for 10 hr on a radial line 25–43 km away from the DVLA. All acoustic events broadcasted low-frequency (61–300 Hz) m-sequences continuously except for a short gap each hour to synchronize transmitter computer files. An auxiliary cruise objective was to obtain high temporal and spatial resolution measurements of the sound speed field between SS500 and the DVLA.

Two methods were used: tows of an experimental "CTD chain" (TCTD) and periodic casts of the ship's CTD. The TCTD consisted of 88 CTD sensors on an inductive seacable 800 m long, and was designed to sample the water column to 500 m depth from all sensors every few seconds. Two tows were conducted, both starting near SS500 and following the path from SS500 towards the DVLA, for distances of 93 km and 124 km. Only several dozen sensors responded during sampling. While the temperature data appear reasonable, only about one-half the conductivity measurements and none of the pressure measurements can be used. Ship CTD casts were made to 1500 m depth every 10 km, with every fifth cast to full ocean depth.

In many areas of Earth science, including climate change research and operational oceanography, there is a need for near real-time integration of data from heterogeneous and spatially distributed sensors, in particular in-situ and space- based sensors. The data integration, as provided by a smart sensor web, enables numerous improvements, namely, 1) adaptive sampling for more efficient use of expensive space-based and in situ sensing assets, 2) higher fidelity information gathering from data sources through integration of complementary data sets, and 3) improved sensor calibration.

Our ocean-observing smart sensor web presented herein is composed of both mobile and fixed underwater in-situ ocean sensing assets and Earth Observing System (EOS) satellite sensors providing larger-scale sensing. An acoustic communications network forms a critical link in the web, facilitating adaptive sampling and calibration. We report on the development of various elements of the smart sensor web, including (a) a cable-connected mooring system with a profiler under real-time control with inductive battery charging; (b) a glider with integrated acoustic communications and broadband receiving capability; (c) an integrated acoustic navigation and communication network; (d) satellite sensor elements; and (e) a predictive model via the Regional Ocean Modeling System (ROMS) interacting with satellite sensor control.

Underwater inductive coupling is used to recharge a lithium-ion battery pack for an underwater mooring profiler operating on a cabled deep-ocean mooring sensor network. The mooring profiler is a motor driven autonomous underwater vehicle that is attached to a vertical mooring cable suspended between the seafloor at 900 m and subsurface float structure at a depth of 160 m (to minimize wave dynamics and bio-fouling). A suite of on-board sensors record data as the mooring profiler travels along the cable which is transferred from the profiler to the sensor network and ultimately to shore over an inductive data link. The on-board batteries are charged inductively when the profiler enters a dock mounted below the float. Power transfer across the inductive couplers is approximately 240 W with 70% efficiency.

Much of the cost and effort of new ocean observatories will be in the infrastructure that directly supports sensors, such as moorings and mobile platforms, which in turn connect to a "backbone" infrastructure. Four elements of this sensor network infrastructure are in various stages of development, presented here: (1) a cable-connected mooring system with a profiler under real-time control with inductive battery charging; (2) a glider with integrated acoustic communications and broadband receiving capability; (3) an integrated acoustic navigation and communication network with tomography on various scales; and (4) a satellite uplink and feedback system. We also present initial results from field experiments, as well as from studies on communication performance of the underwater sensor network system under development.

Much of the cost and effort of new ocean observatories will be in the infrastructure that directly supports sensors, such as moorings and mobile platforms, which in turn connect to a "backbone" infrastructure, such as cabled seafloor nodes. Three elements of this sensor network infrastructure are in various stages of development: a cable-connected mooring system with a profiler under real-time control with inductive battery charging; a glider with integrated acoustic communications and broadband receiving capability; and integrated acoustic navigation, communications, and tomography, and ambient sound recording on various scales.

The objective of the North East Pacific Time-Integrated Undersea Networked Experiments (NEPTUNE) is to establish a permanent, subsea observatory surrounding the Juan de Fuca tectonic plate. To achieve this objective, a special power distribution system is designed to provide continuous power to science equipment, vehicles, and laboratories located as deep as 5 km below the water surface. The NEPTUNE power system is significantly different from terrestrial power systems in many aspects and it requires different switching, protection, and control strategies. In this paper, we address the design of system switching and fault isolation equipment.

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.

An infrastructure for global, regional, and coastal sub-sea observatories is being planned to support individual and networked sensors. Secondary cables and junction boxes, moorings, and downbore tools could extend the horizontal reach by tens to hundreds of km from the primary cable and nodes throughout the water column and down boreholes into the crust. The support infrastructure could include navigation and communications systems, free-swimming AUVs, and bottom rovers that could carry sensors and could provide data and energy "tanker" service.

The NEPTUNE power delivery system faces several challenges in serving the needs of the oceanographic community. Two major challenges, operating the system under normal conditions and protecting it against faults, require the development of new approaches unfamiliar to power engineers. In particular, the power management system must cope with several modes of potential system instability, and the protection system must operate in a deliberately weak system. Furthermore, it is likely that communications will be disrupted in the event of a fault. The approach taken to address these challenges is described.