Sea Technology

APR 2013

The industry's recognized authority for design, engineering and application of equipment and services in the global ocean community

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particle concentration in the water. An ADCP operating at 1-megahertz acoustic frequency is sensitive to zooplankton and other particles with similar size, such as suspended oil droplets. For instance, to understand whale migration and feeding patterns, Woods Hole Oceanographic Institution (WHOI) researchers utilize backscatter data from glider-mounted ADCPs to track zooplankton location in the water column. ters, depending on scattering conditions. The 1-megahertz transducers allow for a small physical size and good return signal strength over the dive profle of 1,000 meters in typical ocean scattering conditions. The instrument uses a fourbeam transducer head that creates different symmetric three-beam arrays: one that can be used on descent and the other on ascent. By measuring during both descent and ascent, the AD2CP provides a more complete data set for post-processing compared to inAD2CP struments capable of sampling only on Since 2005, Nortek AS (Oslo, Norascent or descent. way) has collaborated with leading The AD2CP is equipped with a presresearchers at WHOI, the University sure sensor and a microelectromechanof Washington, Rutgers University, Meical-systems (MEMS) tilt sensor and commorial University, University of California pass capable of measuring throughout the at Santa Barbara, Scripps Institution of large pitch range that gliders experience. Oceanography and iRobot to develop The AD2CP is controlled over a standard The AD2CP. specialized ADCPs and data-processing RS-232 interface from the glider���s main methods to measure current velocity from gliders. In 2012, computer, allowing easy reconfguration and download of Nortek released the AD2CP-Glider (acoustic Doppler curdata subsets that can be transferred to shore using the glidrent profler for gliders) developed specifcally for the chaler communication systems. The interface allows the glider lenges of measuring current velocity from gliders, such as computer to write GPS position data and other relevant dive small size, low power consumption and precise velocity parameters to the AD2CP memory. Onboard memory (SD measurements. The instrument must also be able to tolerate card) provides large storage capacities for long-duration frequent pressure cycling and have a high-quality orientamissions. Fast data download via an Ethernet interface is tion sensor to resolve the pitch and roll angles during deavailable when the AD2CP is retrieved. scent and ascent. The AD2CP uses broadband processing for accurate veMeasurement Challenges locity measurements. It operates at an acoustic frequency of Despite many reasons to measure velocity from glid1 megahertz and provides a profling range of 15 to 30 meers, operational measurements have been slow to become 36 st / April 2013 www.sea-technology.com

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