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Passive Alternatives to Low Frequency Active Sonar,
July 2, 2001
Prepared by Mac Hawley
Benefits of Passive Sonar versus Active Sonar
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Passive sonar does not reveal the listener.
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Passive sonar does not reveal "friendly" submarines.
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Passive sonar causes zero environmental damage whether it is in use one minute or 24 hours a day.
1. New and Upgraded Passive Sonar Systems
Statement of RADM Malcolm I Fages, U.S. Navy Director, Submarine Warfare Division Office of the Chief Of Naval Operations (N87) and RADM J. P. Davis, U.S. Navy Program Executive Office for Submarines before the House Armed Services Committee Military Procurement Subcommittee on Submarine Force Structure and Modernization 27 June 2000.
"Acoustic Superiority. The Submarine Force is making significant, rapid improvements in acoustic sensors and processing. In real-world exercises and operations, both the TB-29 towed array and the new Acoustic Rapid Commercial-Off-The -Shelf (COTS) Insertion (ARCI) sonar system have unequivocally demonstrated our submarines retain a clear acoustic advantage. Use of COTS equipment in ARCI (and in a modified TB-29 array) has substantially reduced costs with significantly improved processing capability. Each ARCI ship-set costs only a small fraction of the price of its predecessor, yet improves processing power by an order of magnitude. This faster and more robust processing power enables us to use powerful new algorithms that result in significantly improved towed array detection ranges. Each modified TB-29 towed array will cost one- half of the price of its predecessor, yet provides equivalent performance. We are also working with the Navy's Chief Technology Officer and the Office of Naval Research to develop even more affordable and reliable towed arrays, specifically fiber optic towed arrays. Fleet Commanders have repeatedly requested ARCI systems at a rate faster than we can afford to provide them."
"Surveillance Towed Array Sensor System (SURTASS) Twin Line operations in 1998 and 1999 demonstrated the ability to detect advanced diesel submarines at substantial ranges in the littoral environment where contact was previously thought to be 'unobtainable' by the operational commander. Two twin-line systems have been delivered using current technology arrays. No additional systems will be delivered next year due to funding constraints. However, follow-on SURTASS twin lines will leverage the submarine TB-29 developments by fielding twin TB-29 arrays. The COTS version of the Fixed Distributed System (FDS-C) starts in-water testing this year. This use of COTS equipment has also resulted in substantially reduced costs with no reduction in fielded capability. Development of the new Advanced Deployable System (ADS) will provide a rapidly deployable acoustic array installed on the ocean floor that provides littoral undersea wide-area surveillance and real time cueing. ADS development is moving along smoothly with potential for accelerated capability development."
2. Robust Passive Sonar
The Defense Advanced Research Projects Agency (DARPA) is the central research and development organization for the Department of Defense (DoD). It manages and directs selected basic and applied research and development projects for DoD, and pursues research and technology where risk and payoff are both very high and where success may provide dramatic advances for traditional military roles and missions.
Dr. Thomas J. Green- Speech given to Dept of Defense -September 6-8, 2000 http://www.darpa.mil/DARPATech2000/presentation.htm
"Good afternoon ladies and gentlemen! My name is Tom Green and I'm the Program Manager for the Robust Passive Sonar Program, otherwise known as R-P-S.
"The focus of R-P-S is to develop innovative, optimal end-to-end processing approaches that exploit tactical acoustic sensors to produce dramatic gains in passive detection against quiet targets operating in shallow water "littoral" environments. In recent years there has been much emphasis on achieving tactical control of shallow water, littoral regions against quiet diesel electric submarines. Towards this end, there has been substantial fundamental work aimed at developing advanced processing techniques to exploit the propagation characteristics of these regions. In addition, new sensors are being developed and deployed that have the necessary characteristics to support many of these processing techniques. We believe there is an opportunity now to realize significant acoustic gain by applying these and other advanced signal processing techniques to emerging sensors within an end-to-end sonar system context and by so doing to achieve substantial tactical advantage over future submarine threats."
Summary Of Noise Pollution Implications for Endangered Marine Species
Towed arrays and ADS are passive, not active, systems. They do not make noise. They do not degrade theater tactics as LFAS does. Use of these systems, as compared to LFAS, mitigates the conflict the Navy is confronted with in LFAS operations; biophysical damage to marine mammals over large ocean areas, and the abrogation of the Navy's environmental stewardship of the sea.
From a noise standpoint, there is no conflict: by using the advanced passive detection systems, and shutting down the acoustically hazardous LFA system, the Navy can fulfill its mission for national security and be stewards of the seas.
Rob Rand-Independent Systems Consultant with over 20 years of experience in environmental noise, acoustics, and systems design. Rob is a member of the Institute of Noise Control Engineering (INCE) and the Audio Engineering Society
(AES).
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