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July 2012 Issue

Navy-Developed Photovoltaic Cells Designed To Power Underwater Sensor Systems
Navy scientists have developed high bandgap solar cells capable of producing sufficient power to operate electronic sensor systems around 9 meters depth, the U.S. Naval Research Laboratory announced in June.

The high-quality gallium indium phosphide (GaInP) cells, at a maximum depth of 9.1 meters, have an output of 7 watts per square meter of solar cells, according to the Navy’s preliminary results. This shows there is useful solar power to be harvested at depths typical of nearshore littoral zones.

Underwater autonomous systems and sensor platforms are severely limited by the lack of long-endurance power sources. Attempts to use photovoltaics have had little success, primarily due to the lack of penetrating sunlight.

Even though the absolute intensity of solar radiation is lower underwater, the spectral content is narrow and lends itself to high conversion efficiency if the solar cell is well matched to the wavelength range. GaInP cells have high quantum efficiency in wavelengths from 400 to 700 nano­meters (visible light) and intrinsically low dark current. The filtered spectrum of the sun underwater is biased toward the blue-green spectrum, and thus higher bandgap cells such as GaInP perform better than conventional silicon cells.


Scripps Researchers Receive Navy Funding
Scripps Institution of Oceanography researchers will receive $4.5 million in U.S. Navy funding to acquire and deploy instruments for six research projects, the institution announced in June. All awards were through the Defense University Research Instrumentation Program (DURIP).

Two DURIP awards will fund observational technology on the hull of the new Navy-owned, Scripps-operated research vessel, AGOR 28. The awards will equip the AGOR 28 with a swath-mapping multibeam echosounder system for seafloor imaging at depths of less than 1,000 meters, two Teledyne RDI (Poway, California) acoustic Doppler current profilers and an ultrashort baseline navigation system.

To improve predictions of waves, weather and climate for naval applications, oceanographer Ken Melville secured funding to deploy Wave Gliders from Liquid Robotics Inc. (Sunnyvale, California) that can measure key variables of air-sea interactions. This data will be compared with information gathered from the Scripps RP FLIP.

Oceanographer Eric Terrill won support for testing a Hydroid (Pocasset, Massachusetts) REMUS 600 AUV configured with specialized sensors to 600 meters depth.

Marine acoustics researcher William Hodgkiss also received an award to design and fabricate a 128-element vertical hydrophone array that will listen to mid-frequency ambient noise in deep water. Data from the array will improve understanding of the dynamics of the mid-frequency ambient noise environment and help develop anti-submarine warfare signal-processing algorithms.


Navy Merger Creates Coastal Riverine Force
The U.S. Navy Expeditionary Combat Command in June established the Coastal Riverine Force (CORIVFOR), a merger of the Riverine Force and Maritime Expeditionary Force. CORIVFOR, composed of 2,500 active and 2,000 reserve sailors, performs maritime expeditionary security missions in green and brown waters. This is meant to bridge the gap between traditional Navy blue-water operations and land-based forces for port and harbor security in vital waterways and maritime infrastructure.

CORIVFOR will utilize larger patrol boats that allow operations among rivers, harbors, littorals and the open ocean.


With Permit for Sonar Testing Nearing Expiration, Navy Evaluates Plan to Triple Sonar Use
The U.S. Navy plans to triple its sonar usage in the near future and is seeking renewal for its five-year permit, which will expire at the end of 2013, from the National Marine Fisheries Service that exempts the Navy from the Marine Mammal Protection Act of 1972.

The Navy held in June five informational meetings for public comment on its sonar usage, which has been growing due to focus on developing anti-submarine warfare and mine countermeasure technologies. A computer model shows, however, that marine mammals in the Navy’s testing area, which runs from Maine to the Gulf of Mexico, would have tens of thousands more chances of being harmed by sonar, according to the Associated Press.

The Navy said it is upping its efforts to protect marine life from sonar. Using its new Navy Acoustic Effects Model, or NAEMO, the Navy will calculate risk to marine mammals by accounting for factors such as animal dive profiles, 3D sound-field propagation and simulated scenarios.


2013:  JAN | FEB | MARCH | APRIL | MAY | JUNE | JULY | AUG | SEPT | OCT | NOV | DEC
2012:  JAN | FEB | MARCH | APRIL | MAY | JUNE | JULY | AUG | SEPT | OCT | NOV | DEC

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