Dr. David A. Sparrow Profile

Dr. David A. Sparrow

Research Staff Member at Institute for Defense Analyses

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Publications (6)

Proceedings Article | 9 May 2006 Paper

Current challenges in autonomous vehicle development

J. Connelly, W. Hong, R. Mahoney, D. Sparrow

Proceedings Volume 6230, 62300D (2006) https://doi.org/10.1117/12.666574

KEYWORDS: Sensors, Robots, Artificial intelligence, Robotics, Unmanned systems, Telecommunications, Databases, Defense and security, Classification systems, Control systems

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Proceedings Article | 4 September 1998 Paper

Phenomenology of prompt gamma neutron activation analysis in the detection of mines and near-surface ordnance

David Sparrow, Lisa Porter, J. Thomas Broach, Roshni Mehta-Sherbondy

Proceedings Volume 3392, (1998) https://doi.org/10.1117/12.324227

KEYWORDS: Scattering, Nitrogen, Absorption, Explosives, Oxygen, Signal attenuation, Sensors, Silicon, Boron, Land mines

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Prompt gamma neutron activation analysis (PGNAA) has been proposed for confirming the presence of energetic materials as part of a mine or unexploded ordnance detection system. Ancore Corporation (previously SAIC Advanced Nucleonics Division), funded through Night Vision Electro Sciences Directorate by Environmental Security Test Certification Program, has carried out proof-of-concept demonstrations of PGNAA in this confirmatory role at Socorro, NM, and Yuma, AZ. In this, the first part of a two-part paper addressing the use of PGNAA in the detection of surface and near-surface UXO, we explore the phenomenology of PGNAA signals from surface or near-surface ordnance in soil to gain insight into the results of those demonstrations. PGNAA uses the high-energy gamma ray (10.8 MeV) from capture on N¹⁴ as a signature of the presence of nitrogen. This is one of the highest energy gamma rays resulting from neutron capture, and nitrogen is a major constituent of explosives, but a small portion of soil. Thus, PGNAA might be effective at confirming the presence of explosives. The phenomenology of dry soil is dominated by the two most common elements, oxygen and silicon. Neutrons injected into the soil elastically scatter from nuclei (predominantly oxygen), losing energy and propagating in a random walk fashion. Once slowed, neutron capture on soil elements produces a broad gamma-ray spectrum. Capture on Si²⁹ produces a 10.6 MeV gamma, which is not resolvable from the nitrogen signal of interest using scintillation detectors. Thus, PGNAA will need either good resolution detectors, or robust background subtraction to estimate the silicon contribution. For any system unable to resolve the Si²⁹ (10.6 MeV) and N¹⁴(10.8 MeV) gammas there is an inherently low signal to background, resulting primarily from the silicon in the soil. After background subtraction, there remains a challenging signal to noise level, where the noise is partly due to counting statistics and partly due to the modeling of the subtracted background.

Proceedings Article | 4 September 1998 Paper

Assessment of thermal neutron analysis applied to surface and near-surface unexploded ordnance detection

Lisa Porter, David Sparrow, J. Thomas Broach, Roshni Mehta-Sherbondy, Joseph Bendahan

Proceedings Volume 3392, (1998) https://doi.org/10.1117/12.324226

KEYWORDS: Sensors, Explosives, Nitrogen, Scattering, Error analysis, Signal detection, Data modeling, Silicon, Germanium, Detection and tracking algorithms

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Proceedings Article | 22 July 1997 Paper

Mine and UXO detection: measures of performance and their implication in real-world scenarios

Thomas Altshuler, Anne Andrews, David Sparrow

Proceedings Volume 3079, (1997) https://doi.org/10.1117/12.280859

KEYWORDS: Land mines, Target detection, Mining, Sensors, Unexploded object detection, Statistical analysis, Electromagnetism, Fourier transforms, Magnetism, Roads

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Mine and unexploded ordnance (UXO) detection systems must function in highly cluttered environments. Clutter leads to false alarms thereby hindering the detection and identification of targets of interest. Since the end user of the mine or UXO detection technology requires both a high detection rate and a low number of false alarms, technology demonstrations and system evaluations are designed to test these measures of performance. Detection rate and false- alarm rate are highly interdependent and must always be evaluated together. The relationship between the two rates directly affects the overall performance of the sensor in the field. Poor performance of a system in either detection rate or false-alarm rate causes a substantial increase in risk of undetected and thus unmarked or unremediated mines or UXO. A system with a low detection rate will leave many mines or UXO undetected. Performance can be traded between probability of detection and false-alarm rate by changing the system threshold. Raising or lowering the threshold will cause both the detections and false alarms to decrease or increase together. A system with a high false-alarm rate result in an increase in the time required to investigate potential targets. Therefore the rate of advance and rate of clearance decrease. With limited clearance resources, site coverage may become too time consuming or costly for operationally effective clearance, resulting in risk from undetected mines and UXO in areas that have not been searched. An assessment of the connection between detection rate nd false-alarm is presented. This relationship is discussed in the context of several government-sponsored in- field technology demonstrations of prototype and commercially available mine and UXO detection technologies, as well as real clearance operations. Implications of the results of these tests and the measures of performance are discussed in the context of real-world operations, including scenarios for clearance of miens in Bosnia and of UXO at DoD sites.

Proceedings Article | 20 June 1995 Paper

Performance assessment at the Jefferson Proving Ground demonstration of systems for the detection and identification of buried unexploded ordnance

Michael Mulqueen, Vivian George, Anne Andrews, David Sparrow, Regina Dugan

Proceedings Volume 2496, (1995) https://doi.org/10.1117/12.211361

KEYWORDS: Target detection, Detection and tracking algorithms, Environmental sensing, Sensors, Signal to noise ratio, General packet radio service, Sensor performance, Magnetometers, Defense and security, Contamination

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Proceedings Article | 9 June 1994 Paper

Signal processing approaches to radio frequency interference (RFI) suppression

Matthew Braunstein, James Ralston, David Sparrow

Proceedings Volume 2230, (1994) https://doi.org/10.1117/12.177172

KEYWORDS: Electromagnetic coupling, Interference (communication), Signal processing, Synthetic aperture radar, Radar, Receivers, Data modeling, UWB radar, Algorithm development, Antennas

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Ultra-wideband radar (UWB) has been shown to be among the most powerful techniques available for underground and obscured object detection. The value of such systems is that they combine the penetration enhancement associated with VHF/UHF (and lower) frequencies with the resolution of wide absolute bandwidth. Such systems necessarily make use of much of the frequency spectrum already in heavy use by other services, such as television and mobile communications. Although this spectral overlap provides occasion for adverse consequences in both directions, to date the principal consequence has been often-severe impact on UWB radar measurements. Even in remote locations, the average interference power often exceeds receiver noise by many dB, becoming the limiting factor on system sensitivity. Nor are UWB radar designers free to overcome this interference by increasing radar power, since regulatory sanction for UWB operation will depend on maintaining sufficiently low spectral power densities to assure that other, prior, services are not appreciably degraded. Given the importance of radio frequency interference (RFI) on practical ultrawide band ground penetrating radar systems, it is important to consider how and to what extent the effects of RFI noise may be reduced. The overall problem of RFI and its impacts will be described and several signal processing approaches to removal of RFI will be discussed. These include spectral estimation and coherent subtraction algorithms and various filter approaches, which have been developed and applied by the signal processing community in other contexts. These methods will be applied to several different real-world experimental data sets, and quantitative measures of the effectiveness of each of these algorithms in removing RFI noise will be presented. Although computationally-intensive, most of the techniques to be described achieve substantial increases in S/RFI without requiring concomitant increases in radar average power.

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