Technology for the United States Navy and Marine Corps, 2000-2035 Becoming a 21st-Century Force : Vol. 7, Undersea Warfare (0) / Chapter Skim
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Whatever the conditions, it is clear that the undersea environment is an extremely complex and dynamic medium, and naval forces must be able to surveil and control (i.e., dominate) this battle space to the degree necessary to accomplish their mission.
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Robust technological opportunities exist by which U.S. ASW capabilities can be enhanced to deal with future submarine threats.
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Since it is highly unlikely that a technology will emerge that can render the mine threat harmless, MCM will continue to be based on a number of discrete systems and techniques arranged in a balanced system of systems. This would include appropriate technologies that range from brute force methods to smart weapons and systems that can be either tethered or autonomous.
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· Using advances in sensors, signal processing, and computational power, autonomous or semiautonomous systems can be netted in an undersea surveillance system that uses distributed sensors and small undersea vehicles or bottom crawling devices to provide covert mine surveillance, deletion, and neutralization capabilities. These would be "smart" systems, with communications capability to operate autonomously in the most efficient manner, thereby avoiding personnel and platform losses.
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· Aggressively pursue the development of so-called brute force technologies that will neutralize mines and obstacles in the very shallow water zone, the surf zone, and the craft landing zone.
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Develop the lightweight hunting and sweeping technologies required for these smaller units. · Apply reasonable mine shock hardening and effective acoustic and magnetic signature reduction technologies to all new-construction ships.
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The United States has vital economic, political, and military interests and commitments around the globe. Recognizing this fact, the National Military Strategy1 states that naval forces ".
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The who, what, and when of future submarine threats remain uncertain. Suffice it to say, however, that global interest in advanced submarine capabilities continues to provide the clear potential for credible submarine opposition in future conflicts.
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Uppal, commented in 1994 that developing nations desire submarine forces because they are a cost-effective platform for the delivery of several types of weapons;4 they counter surface forces effectively; they are flexible, multimission platforms (e.g., antisurface warfare (ASUW) , special forces, intelligence and warning, and ASW)
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It is a misconception that littoral waters are always shallow. Although it is true that shallow waters are always in littoral areas, an examination of the bathymetry of potential regional conflict areas reveals that the littoral regions encompass the full range of depths from deep to shallow.
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There are no quick fixes, however; a dedicated, focused research effort will be required to develop and effectively deploy these solutions. For example, advanced signal processing techniques must be coupled with a thorough understanding of target and environmental parameters and their variabilities.
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Signal processing algorithms based on coherent, range-dependent propagation codes using real-time environmental inputs now can exploit this coherence. · The reduction of wide-band threat signatures in the VLF band is difficult because it involves the entire platform, and hull coatings are less effective at damping these long-wavelength acoustic signals.
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The necessary components of an effective ASW technology development program are as follows: · Well-posed science and technology; · At-sea experiments with sensors that are both well calibrated and accurately navigated to provide real-time environmental data; · Fundamental exploitation of the advances in ocean acoustics, oceanography, and signal processing; Robust ocean engineering for their deployment; Integration of communications, navigation, and high-speed computation; and · Highly trained operators. At the end of the Cold War the merging of these components showed prom
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Many of the expected future performance gains will likely come from more capable arrays that exploit both horizontal and vertical properties of the signal field. One can look to the oil exploration industry to contemplate what is now possible.
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In radar this is termed space-time beam forming and leads to impressive noise suppression for both clutter and jamming, yet it has not been explored in sonar. Coherent sonar signal processing can be considered a generalized form of matched filtering, so that spatial and temporal replicas, or matching signals, are required for implementation.
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This fully coherent processing technique incorporates environmental data for wide-band prediction of the signal and noise fields. It also uses coherence limits of the propagation to establish array lengths and coherent processing intervals, as well as the division between the coherent and incoherent sections of the sonar signal processor.
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Now, there is greater understanding of the algorithms and their limitations, and new algorithms are being developed, so that more robust and stable implementations of adaptive beam forming are expected to be available soon. It is important to emphasize that fully coherent processing and adaptive processing are different issues, although they can reinforce each other.
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Experiments with adaptive beam forming on both arrays are demonstrating impressive results especially for cluttered environments. For surface ships, the twin line SURTASS has been deployed, and systems with multiline arrays are in advanced development.
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, which has already been deployed, has demonstrated the utility of depth-of-field beam forming in tactical scenarios. Advances in low-noise sensors and signal processing should improve conformal array performance at mid frequencies.
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enable beam forming while maneuvering. Similarly, sensor response variability caused by structural inhomogeneities leads to the same liabilities in achieving high gains for mounted and conformal arrays.
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Several towed array experiments have demonstrated this as well. Passive ranging information is very useful for tactical ASW and should be a feature available in all future beam forming systems.
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The coverage that a fixed system can provide against modern quiet threats will not have basin scales, but the performance can be maximized with imperatives described earlier. Wide apertures with sensor numbers far exceeding those of SOSUS, the use of fully coherent processing with accurately navigated arrays, adaptive beam forming, and the exploitation of Doppler all can be used with the same measures of effectiveness.
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Coherence in deep water is greater than in the littoral, especially when the signals are not bottom interacting. This presents an opportunity to significantly increase detection ranges by pushing coherence to the limits.
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It implemented a simple form of adaptive beam forming, with the array shape compensation from the positioning system. The gains with even this simple form of adaptive beam forming were impressive when operating in a high-clutter, shipping lane environment.
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Although there have been many theories and experiments addressing the issues of spatial and temporal coherence, the limits have yet to be established for the environments and spectral bands where ASW operates. Careful experiments with accurate environmental data and modeling have frequently revealed coherence scales larger than those predicted by theories and simulations.
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