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Mitigation of Biologically Induced Active Sonar Reverberation in Littoral Regions


OBJECTIVE: The objective is to develop technology to improve performance of active sonar by reducing the effect of biological backscattering in littoral regions. DESCRIPTION: Sonar performance is degraded in littoral waters because of the abundance of marine life. Resonant backscattering from marine life (fish air bladders, for example) reduces signal to noise ratio by increasing the background level and by mimicking targets. Current sonar systems lack the ability to discriminate between targets and clutter caused by marine life, reducing the ability to perform detection, classification and localization of targets (references 1-5). Past efforts to improve active sonar performance in the littorals with existing state of the art systems, such as the AN/SQS-53C, have included waveform development and data fusion techniques. Current research has targeted using characterization of fish bladder resonance in classification techniques (references 6-8). Targeting reduction of reverberation prior to classification based on an understanding of the effect of biologics is a largely unexplored area of investigation. The Navy is seeking concepts, processing, or techniques beyond state of the art, which will ameliorate the resonant backscattering due to biologics. Extant research on the characteristics of biologically induced backscattering exists that can be exploited to develop technology that reduces the backscattering effects of marine life in existing active sonar systems. Innovation is sought to develop methods that incorporate the resonant characteristics of marine life to reduce their backscattering effects on active sonar. These innovative methods may include, but are not limited to, signal processing algorithms, transmission/operational characteristics, and system hardware. Methods should address not only capability, but also cost effectiveness. The resulting technology should provide a significant improvement in the performance and detection capability of active sonar by reducing the number of false contacts and improve operator work load by decreasing the amount of display clutter. The technology will be integrated into sonar system processing to improve performance and detection capability. The Phase I effort will not require access to classified information. If need be, data of the same level of complexity as secured data will be provided to support Phase I work. The Phase II effort will likely require secure access, and the contractor will need to be prepared for personnel and facility certification for secure access. PHASE I: The company will develop concepts to ameliorate acoustic resonant biological backscattering that meets the requirements described above. The company will demonstrate the feasibility of the concepts in meeting Navy needs and will establish that the concepts can be feasibly developed into a useful product for the Navy. Feasibility will be established by testing and analytical modeling. The small business will provide a Phase II development plan with performance goals and key technical milestones, and that will address technical risk reduction. PHASE II: Based on the results of Phase I and the Phase II development plan, the small business will develop a concept, process, or technique prototype for evaluation as appropriate. The prototype will be evaluated to determine its capability in meeting the performance goals defined in the Phase II development plan and the Navy requirements for the active sonar. System performance will be demonstrated through prototype evaluation and modeling or analytical methods over the required range of parameters including numerous deployment cycles. Evaluation results will be used to refine the prototype into an initial design that will meet Navy requirements. The company will prepare a Phase III development plan to transition the technology to Navy use. PHASE III: If Phase II is successful, the company will be expected to support the Navy in transitioning the technology for Navy use. The company will develop improved active sonar for evaluation to determine its effectiveness in an operationally relevant environment. The company will support the Navy for test and validation to certify and qualify the system for Navy use. PRIVATE SECTOR COMMERCIAL POTENTIAL/DUAL-USE APPLICATIONS: Commercial active sonars that experience biologically induced backscattering may incorporate this technology, for example, it could be used for bottom and sub bottom profiling. One industry would include mapping for cable laying. REFERENCES: 1. Bell, Thaddeus, Probing the Ocean for Submarines, a History of the AN/SQS-26, 2nd edition, Los Altos Hills, CA, Peninsula Publishing, 2011 2. Chapman, R.P."Deep scattering spectra in Atlantic and Pacific", Journal of the Acoustical Society of America, Volume 56, Issue 6 December 1974: pp. 1667-1672. 3. Farquhar (Ed.) 2 April 1970 International Biological Scattering Conference, Weston paper on shallow biologics, pg 212 4. Love, R.,"Resonant scattering by swimbladder-bearing fish", Journal ofAcoustical Society of Americaoc. Issue 64, 1978: pp. 571580. 5. Love, R., Thompson, C., and Nero, R.,"Changes in volume reverberation from deep to shallow water in the eastern Gulf of Mexico", Journal AcousticalSociety of America. Issue 114, 2003: pp. 26982708. 6. Stanton, Chu, Jech."Acoustic Resonance Classification of Swimbladder-Bearing Fish", Office of Naval Research. 2010, Office of Naval Research. 3 May 20127. Stanton, Chu, Gauss."Acoustic Resonance Classification of Swimbladder-Bearing Fish at Multiple Scales", Office of Naval Research. 2010, Office of Naval Research. 3 May 20128. Gauss, Love."Moment-Based Physical Models of Broadband Clutter due to Aggregations of Fish", Office of Naval Research. 2011, Office of Naval Research. 3 May 2012
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