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Improving False Alarm Rate For ASW, MCM Operations

By Dr. Jim Byrnes

MIRK corrects matched-filter false alarms.

The U.S. Navy's unmet operational needs (UONs), including the anti-access/area denial (A2/AD) threat, extend both to the antisubmarine and sea mine countermeasures (MCM) realms of naval undersea warfare. 'The most persistent problem in both ASW [anti-submarine warfare] and MCM are the many target false alarms incorrectly classified as targets from sonar sensors,' said R.Adm. John Pearson, U.S. Navy (retired), the 1980 winner of the U.S. Navy Surface Force, Atlantic Fleet Anti-Submarine Warfare Award and commander of the U.S. Navy Mine Warfare Command from 1991 to 1996. 'This adversely affects real-time sonar operators' decisions, remote-sensor post-mission analysis decisions, unnecessarily wastes scarce and very expensive weapons, and injects significant time delays in detect-to-engage sequences.'

Possessing the potential to be a game changer for this persistent problem, MIRK (Material Identification Reflectivity Kernel) is a mathematical, signal-processing technique being developed as a software upgrade to existing sonar systems. MIRK is among the 34 Rapid Innovation Fund (RIF) white papers funded by the U.S. Navy in fiscal year (FY) 2011, chosen from several thousand submissions. According to the U.S. Department of Defense, MIRK 'provides the warfighter the capability to reliably detect bottomed submarines and mines in real time with fewer false alarms, significantly increasing the fleet's ability to defeat anti-access/area denial (A2/AD) threats.'

Pearson surmised, 'In the near term, [MIRK] can provide sonar operators with an accurate decision capability not available before now. In the midterm, based on experience with ongoing contract work on various sensors, we will gain confidence and learn enough to move MIRK to an automatic target recognition [ATR] capability. This will result in highly significant improvements in our ASW/MCM capabilities.'

Sonar Applications
MIRK is significant in sonar applications for two major reasons. First, it enables a classification decision, moving the classification or characterization beyond 'possible' target to 'probable' or 'positive' target. It can discriminate between manmade and nonmanmade ensonified objects, be they submarine or sea mine, in the midst of significant environmental clutter and/or reverberation. Second, because MIRK uses existing digital active acoustic system capabilities, it can add to the performance of many types of currently fielded systems without costly hardware modifications.

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 coefficients: Young's modulus and others for elastic materials, and permittivity, conductivity and others for dielectric materials. These coefficients have been measured in laboratories, derived through physics and computed for validation. A kernel that encapsulates these coefficients, the reflectivity kernel, can be associated to classes of materials. Prometheus Inc. (Sharon, Massachusetts), a small, woman-owned mathematics and engineering research firm 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 reflectivity kernel from sonar and radar returns. To continue this article please click here.

Dr. Jim Byrnes, formerly a professor of mathematics at the University of Massachusetts, has headed Prometheus Inc. since its inception in 1983. He is well known in the field of applied harmonic analysis. In addition to leading many significant applied mathematical efforts for the United States Department of Defense, Dr. Byrnes has organized and directed nine NATO advanced study institutes. These intensive two-week courses bring together international experts from academia, government and industry for further development in the fields of digital signal processing, imaging and detection, wavelets and other areas at the intersection of mathematics and engineering.

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