Sea Technology

NOV 2013

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

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(Left) MIRK processing extracts the refectivity kernel. (Bottom) MIRK distinguishes different materials placed in identical physical environments. ties, it can add to the performance of many types of currently felded systems without costly hardware modifcations. The effects of elastic materials on sonar and dielectric materials on radar returns have been observed by divers, radar operators, engineers and physicists since World War II. Each material has quantitative coeffcients: Young's modulus and others for elastic materials, and permittivity, conductivity and others for dielectric materials. These coeffcients have been measured in laboratories, derived through physics and computed for validation. A kernel that encapsulates these coeffcients, the refectivity kernel, can be associated to classes of materials. Prometheus Inc. (Sharon, Massachusetts), a small, woman-owned mathematics and engineering research frm that specializes in the application of high-level mathematics to signal processing, modeling and simulation, has developed unique digital signal-processing methods for extracting this material information refectivity kernel from sonar and radar returns. The refectivity kernel contains material composition characteristics, which provide information necessary to discriminate the echo return as "target of interest" versus "nontarget." The algorithm is both mathematically and numerically stable and tunable for different transmitted signals in many different sensor applications tested thus far with both synthetic aperture radar and sonar data. This capability has been proven during testing on each of several real-world U.S. Navy sonar datasets during the past year. For integration into an operating sonar, the MIRK algorithm potentially provides processing of the sonar echo returns to determine classifcation and discrimination be- tween real targets and false targets. This MIRK determination is provided to an existing sonar decision architecture as an augmenting input for decision making. MIRK can process in real time, has performed robustly in low signal-to-noise ratio returns and is computationally effcient, which results in ease of integration into existing sonar systems. This signal-processing technique could improve classifcation and reduce false target rates in a variety of existing undersea sonar systems to a signifcant degree. The technique only requires a software upgrade to an operational digital sonar system. The technique was successful in its initial radar application in all three U.S. government-funded Small Business Innovation Research (SBIR) phases and transitioned into a program of record for an airborne U.S. Air Force synthetic aperture radar. The Naval Sea Systems Command is funding further development and potential integration of the MIRK algorithm into an existing organic anti-submarine warfare sonar system through the Advanced Processing Build program. November 2013 / st 11

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