This paper describes development and application of a novel method to accomplish real-time solid angle acoustic direction finding using two 8-element orthogonal microphone arrays. The developed prototype system was intended for localization and signature recognition of ground-based sounds from a small UAV. Recent advances in computer speeds have enabled the implementation of microphone arrays in many audio applications. Still, the real-time presentation of a two-dimensional sound field for the purpose of audio target localization is computationally challenging. In order to overcome this challenge, a crosspower spectrum phase1 (CSP) technique was applied to each 8-element arm of a 16-element cross array to provide audio target localization. In this paper, we describe the technique and compare it with two other commonly used techniques; Cross-Spectral Matrix2 and MUSIC3. The results show that the CSP technique applied to two 8-element orthogonal arrays provides a computationally efficient solution with reasonable accuracy and tolerable artifacts, sufficient for real-time applications. Additional topics include development of a synchronized 16-channel transmitter and receiver to relay the airborne data to the ground-based processor and presentation of test data demonstrating both ground-mounted operation and airborne localization of ground-based gunshots and loud engine sounds.

Recently, the need of monitoring parking places, airports, and harbours has increased. Microwaves, infrared based techniques, vision, or acoustics are the key techniques but each of them requires a specific kind of post-processing. Far field target localization methods based on Angle Of Arrival (AOA) often neglect the possibility of erroneous angle observations. Three different methods for increasing the accuracy of cross fixing based localization are compared. Average of the AOAs is easily corrupted by outliers, "m out of k"-selection of AOAs suffers from loss of data. Signal energy based target location circle is used to validate the cross fixing result, thus improving reliability. The energies of averaged target signals from two arrays are used to calculate a circle on which the target resides. Distance from the cross fixed location to the circle is used to validate the location. Experiments are carried out with simulated and real data.

Recently, the need to monitor restricted areas has increased. Acoustics is one of the available key techniques but there are some restrictions and constraints to consider. In situations with unknown noise and low SNR the performance of time delay based direction of arrival (DOA) estimators collapses rapidly as SNR decreases. Outliers are introduced into estimation results when signals of interest are masked by noise. There exist several methods for compensation of noise induced errors, such as averaging within subarrays, time delay selection or various minimizations. These compensation methods provide an optimum solution with respect to some criteria, but are uneffective against large errors in multiple time delays. In this paper, we present a method for removing outlayers caused by errors in time delays. First, we utilize signal propagation speed to measure an error criterion for DOA estimates. Second, estimates with sufficiently large error criterion are identified as outlayers and discarded. Effectiveness of our method is verified through experiments with simulations and real data. In both cases we are able to identify and discard outlayers and thus improve estimation reliability. Results indicate that the given method can be used to gain efficiency and robustness in DOA estimation applications, such as automatic acoustic surveillance of large areas.

Infrasonics offers the potential of long-range acoustic detection of explosions, missiles and even sounds created by manufacturing plants. The atmosphere attenuates acoustic energy above 20 Hz quite rapidly, but signals below 10 Hz can propagate to long ranges. Space shuttle launches have been detected infrasonically from over 1000 km away and the Concorde airliner from over 400 km. This technology is based on microphones designed to respond to frequencies from .1 to 300 Hz that can be operated outdoors for extended periods of time with out degrading their performance. The US Army Research Laboratory and Los Alamos National Laboratory have collected acoustic and infrasonic signatures of static engine testing of two missiles. Signatures were collected of a SCUD missile engine at Huntsville, AL and a Minuteman engine at Edwards AFB. The engines were fixed vertically in a test stand during the burn. We will show the typical time waveform signals of these static tests and spectrograms for each type. High resolution, 24-bit data were collected at 512 Hz and 16-bit acoustic data at 10 kHz. Edwards data were recorded at 250 Hz and 50 Hz using a Geotech Instruments 24 bit digitizer. Ranges from the test stand varied from 1 km to 5 km. Low level and upper level meteorological data was collected to provide full details of atmospheric propagation during the engine test. Infrasonic measurements were made with the Chaparral Physics Model 2 microphone with porous garden hose attached for wind noise suppression. A B&K microphone was used for high frequency acoustic measurements. Results show primarily a broadband signal with distinct initiation and completion points. There appear to be features present in the signals that would allow identification of missile type. At 5 km the acoustic/infrasonic signal was clearly present. Detection ranges for the types of missile signatures measured will be predicted based on atmospheric modeling. As part of an experiment conducted by ARL, sounding rocket launches have been detected from over 150 km. A variety of rockets launched from NASA’s Wallops Island facility were detected over a two year span. Arrays of microphones were able to create a line of bearing to the source of the launches that took place during different times of the year. This same experiment has been able to detect the space shuttle from over 1000 km on a regular basis. These two sources represent opposite ends of the target size, but they do demonstrate the potential for the detection and location of rocket launches.

Silicon micromachining techniques permit batch fabrication of microphones that are small, reproducible, and inexpensive. However, many such sensors have limited bandwidth or are too fragile to be used in a humid, wet, or dusty outdoor environment. Microphones using capacitive micromachined ultrasonic transducer (CMUT) membranes and radio frequency (RF) detection overcome some of the problems associated with conventional micromachined microphones. CMUT membranes can be vacuum-sealed and still withstand atmospheric pressure and submersion in water. In addition, the membrane mechanical response is very flat from dc up to hundreds of kilohertz. A very sensitive RF detection scheme is necessary to detect the small changes in membrane displacement that result from utilizing smaller membranes. In this paper, we present the theory and recent experimental results of RF detection with CMUT membranes. Measurements of a sensor with 1-mm² area demonstrate a flat output response of the acoustic sensor from a fraction of 1 Hz to over 100 kHz, with a sensitivity at 1 kHz of 65 dB/Pa in a 1-Hz noise bandwidth.

Findings are presented from the first year of a joint project between the U.S. Army Engineer Research and Development Center, the U.S. Army Research Laboratory, and the Sandia National Laboratories. The purpose of the project is to develop a finite-difference, time-domain (FDTD) capability for simulating the acoustic signals received by battlefield acoustic sensors. Many important effects, such as scattering from trees and buildings, interactions with dynamic atmospheric wind and temperature fields, and nonstationary target properties, can be accommodated by the simulation. Such a capability has much potential for mitigating the need for costly field data collection and furthering the development of robust identification and tracking algorithms. The FDTD code is based on a carefully derived set of first-order differential equations that is more general and accurate than most current sound propagation formulations. For application to three-dimensional problems of practical interest in battlefield acoustics, the code must be run on massively parallel computers. Some example computations involving sound propagation in a moving atmosphere and propagation in the presence of trees and barriers are presented.

Non-linear signal processing algorithms, developed originally by R.A. Wagstaff for ocean acoustics and named "AWSUM(K)," have been applied in this laboratory to atmospheric acoustic signals measured in the presence of severe intermittent noise. It has been found that the AWSUM(K) processors, which filter out strong signals and pass weak signals, can provide dramatic gains in the signal-to-noise ratio for a steady sinusoidal signal strongly degraded by intermittent manmade noise and intermittent wind noise. Further, applications of the processors to field data have shown a number of systematic behaviors that so far have not been explained or understood quantitatively. This article presents a theoretical analysis of the AWSUM(K) processors for a steady sinusoidal signal in the presence of exponential (Rayleigh) noise and intermittent (non-Rayleigh) noise. The theory quantitatively explains the observed behaviors of the AWSUM(K) processors. In particular, it is shown that in the limit of large sample number, the AWSUM(K) gain in the (signal+noise)-to-noise ratio is independent of the sample number and processor order (for K≥2). For a steady sinusoidal signal, the gain is determined solely by the shape of the noise distribution function near zero. For Rayleigh noise, for example, the gain is given by exp(SNR)/(SNR+1), where SNR is the usual linear signal-to-noise ratio (e.g., SNR = 1 corresponds to a signal-to-noise ratio of 0 dB). For intermittent manmade noise and intermittent wind noise, the measured noise distribution function is strongly peaked near zero, so that gains in approaching 20 dB are predicted, even for small values of SNR. The predictions are in accord with field data from an atmospheric sound propagation experiment.

Networks of unattended acoustic ground sensors can be used to detect and accurately track high-speed airborne acoustic sources. While it is possible, in principle, to estimate altitude using networks of two-dimensional microphone arrays, the high sensitivity of this configuration significantly limits performance. This work shows that the addition of elevated microphones and appropriate signal processing can significantly improve performance. Airborne source tracking results from a field experiment are compared for the use of a small orthogonal three-microphone ground plane array versus the same array with an elevated microphone added.

Polyaniline, an inherently conducting polymer, was synthesized and fabricated as an acoustic membrane enclosure for the packaging of a MEMS-based acoustic microsensor. The packaging was designed to minimize environmental ambient impact, including dust and excess moisture, but maximize microphone performance. Free-standing films of emeraldine base polyaniline were doped with metal salts of aluminum acetoacetate, iron acetoacetate, copper acetoacetate, or titanium ethoxide. Polymer-metal hybrid compositions were analyzed by scanning electron microscopy (SEM) and deconvoluting X-ray photoelectron spectra (XPS) to discern interactions between metal atoms and polyaniline. Mechanical properties of the material, specifically the glass transition temperature and elastic and imaginary moduli, were measured by dynamic mechanical analysis (DMA) as a function of metal type, mechanical excitation frequency and temperature. The hybrid materials were then formed and shaped as flat membranes or as shaped domes of variable radii of curvature,, including hemispherical. Acoustic transmission properties of metal-doped planar and dome-shaped membranes were measured by insertion loss as a function of acoustic frequency between 100 to 2000 Hz in a plane wave tube. Results indicated an effect of metal type upon incorporation into polyaniline, which showed increases in mechanical stiffness and acoustic resonance frequency consistent with increased metal-polymer interaction. Acoustic performance was compared to a numerical model of sound transmission through hemispherical domes as a function of sound frequency, membrane structure, modulus of elasticity, thickness, and source angle of incidence.

Forsvarets forskningsinstitutt (Norwegian Defence Research Establishment) is currently working on a program to develop improved models for both emission and propagation of acoustic waves from ground vehicles, to enable prediction of vehicle signatures as observed by remote sensors. The main purpose of this work in progress is to use such models as an aid to develop improved signal processing methods and pattern recognition algorithms for detection, classification and tracking of military vehicles with acoustic sensors.

Unattended ground sensor technology used for battlefield awareness and other wide area surveillance applications requires state-of-the-art algorithms to address the unprecedented challenges faced in detecting, classifying and tracking military combat vehicles. The performance of traditional acoustic sensor systems often degrades unacceptably against the dynamic and highly mobile multiple target environments in which today's forces must operate. In the present work, a target counting algorithm has been developed to solve problems attributed to unstable tracking performance by resolving track loss deficiencies inherent to closely spaced target environments. The algorithm provides a way to discriminate between vehicles as they pass through an acoustic "trip-line" formed by a sensor in a predetermined field of view (FOV). The proposed approach is realized through an adaptive beamforming algorithm that achieves enhanced directivity in a principal look direction by significantly reducing the effects of interferers outside the precise bearing of the steering direction. The classification algorithm described herein facilitates a minimal representation for features extracted from harmonically related structures characteristic to acoustic emissions from ground vehicles found in battlefield environments. The reduced feature space representation exploits an ordering for the principal narrowband components found in a vehicle's engine noise and has proven effective in solving fundamental problems associated with discriminating between vehicles in variable SNR environments. The performance of the algorithms is demonstrated using signature data collected during various acoustic sensor field test experiments.

Our goal for this study is to construct classifiers with minimum classification error rates for three binary classification problems based on their acoustic emissions, namely tracked versus wheeled vehicles, heavy-tracked versus light-tracked vehicles, and heavy-wheeled versus light-wheeled vehicles. Because the acoustic measurements of a run correspond to tens or hundreds of seconds, and are time-varying, we segment them into one-second data blocks, and use the data blocks (which we call prototypes) for classification. The magnitudes of the second through 12th harmonics of each prototype are used as the features. We find, by analyzing the features within each run and across runs, that the run-means and run-standard-deviations of the features vary from run to run for all kinds of vehicles. We therefore use type-2 fuzzy sets to model the uncertainties contained in these features, and then construct type-2 fuzzy logic rule-based classifiers (FL-RBC) for these three binary classification problems. To evaluate the performance of the type-2 FL-RBCs in a fair way, we also construct the Bayesian classifiers and type-1 FL-RBCs, and compare their performance through leave-one-out experiments. Our experiments show that both the type-1 and type-2 FL-RBCs have significantly better performance than the Bayesian classifier, and the type-2 FL-RBC has better performance than the type-1 FL-RBC for all three classification problems. So we conclude that the type-2 FL-RBCs are the desired classifiers for these three binary classification problems.

The use of an optical fiber as a distributed sensor for detecting, locating, and (with suitable signal processing) classifying intruders is proposed. Phase changes resulting from either the pressure of the intruder on the ground immediately above the buried fiber or from seismic disturbances in the vicinity are sensed by a phase-sensitive optical time-domain reflectometer (Φ-OTDR). Light pulses from a cw laser with a narrow (kHz range) instantaneous linewidth and low (MHz/min range) frequency drift are injected into one end of the single mode fiber, and the backscattered light is monitored with a photodetector. Results of analyses and experimental studies to establish the feasibility of the concept are described. Simulations predict a range of 10 km with 35 m range resolution and 30 km with 90 m range resolution. Experiments indicate adequate (several π-rad) phase changes are produced by intruders on foot for burial depths in the 20 - 40 cm range in sand and in clay soils. A phase perturbation in a fiber has been detected and located in a laboratory demonstration of the Phi-OTDR using an Er:fiber laser as the light source. This technology could in a cost-effective manner provide enhanced perimeter security for nuclear power plants, electrical power distribution centers, storage facilities for fuel and volatile chemicals, communication hubs, airports, government offices, military bases, embassies, and national borders.

An investigation of the feasibility of detecting structures buried underground through passive listening techniques will be presented. Passive detection of structures will be analyzed using elastic wave sources originating inside the structure and from sources exterior to the structure and on the surface. The primary method of investigation will be numerical models using the finite-difference time-domain method (FDTD). A source inside the structure excites elastic waves in the structure, a portion of which travel upward along the walls of the structure and onward to the surface. An alternate form of excitation is a source such as a train, large vehicle, or an explosion located on the surface, away from the structure. Waves from this source interact with the structure and a portion of them travel up from the structure to the surface. An array of sensors is constructed to map the field at the surface and to determine the location and basic characteristics of the structure. Generally, structures examined will be on the order of the size of an underground tunnel complex or buried room and elastic wave sources will be in the low frequency range of large machinery or vehicles.

Tactical capabilities of single and three axis geophones for seismic detection and bearing estimation for homeland security and defense applications are described. It is shown that typically three axis geophones yield a high bearing estimation error. An alternate bearing estimation approach is based on using the time delay in footstep signal detection from three triangulated single axis vertical geophones. In this approach the standard deviation of the bearing estimation error is less than 12 degrees for a walking person distance of 10 to 70m and geophone distances of 8 to 9 m. We find that using the three-axis geophone approach makes it harder for path tracking and bearing estimation within the tactical zone area. We report that a single-axis geophone approach for riangulation of walking person is more effective. In addition, road monitoring is also more efficient using a single-axis geophone approach. We compare the relative and absolute improvement of bearing estimation probability for road monitoring using three single-axis geophones versus 1, 2 and 3 three-axis geophones. We will also discuss the use of single axis vertical geophone sets for monitoring various zone sizes.

A 3-axis magnetometer has been constructed using 3 Spin Dependent Tunneling (SDT) magnetic field sensors as transducers. This magnetometer has been designed for use in Unattended Ground Sensor (UGS) applications. As such, there has been an emphasis on low cost, size, and power. The present version is smaller than previous versions, and is ready for prototype sampling. This paper describes the basic properties of the SDT 3-axis magnetometer, including size, power, and noise floor.

An uncooled bolometric FLIR UGS camera is proposed that provides a full 360° FOV. This camera makes use of a 160x120 pixel bolometric FPA which is operated in random access readout mode and a ground-breaking optics forming image in all directions without moving parts, allowing such imaging with no increase in power consumption with respect to a camera with a unidirectional FOV. This novel IR imaging optics can be further equipped with a supplementary objective to provide passive observation of the sky or another fixed direction. The 360° FOV objective is expected to have f/1, to show an MTF value greater than 50% at the FPA Nyquist frequency, and to yield a thermal resolution better than 100 mK.

We describe the application of image processing techniques for data refinement in sensor networks, by mapping network nodes to pixels in an image. Due to their localized, distributed nature, these techniques are inherently scalable and therefore desirable for use in large sensor networks. We examine two specific problems: cleaning of uncorrelated sensor noise, and the decentralized detection of edges (such as the perimeter of a chemical leak). Our simulation results show that the performance of these processing techniques depends critically upon both sensor density and radio range.

Architecture and technology of imaging intrusion detection sensor OPAK are presented. Applications and desired features for IDS and UGS are compared. Started developments of OPAK towards an unattended ground sensor system are described.

BAE SYSTEMS has been developing and producing uncooled microbolometer sensors since 1995. Recently, uncooled sensors have been used on Pointer Unattended Aerial Vehicles and considered for several unattended sensor applications including DARPA Micro-Internetted Unattended Ground Sensors (MIUGS), Army Modular Acoustic Imaging Sensors (MAIS), and Redeployable Unattended Ground Sensors (R-UGS). This paper describes recent breakthrough uncooled sensor performance at BAE SYSTEMS and how this improved performance has been applied to a new Standard Camera Core (SCC) that is ideal for these unattended applications. Video imagery from a BAE SYSTEMS 640x480 imaging camera flown in a Pointer UAV is provided. Recent performance results are also provided.

Miniature unmanned aerial vehicles (UAVs) are a category of aircraft small enough to be transported, launched, operated, and retrieved by a crew of one or two. The concept is not new, having been in limited use by the U.S. military over the past fifteen years, but interest in potential applications is growing as size and cost of the vehicles come down. An application that is particularly significant to the military and law-enforcement agencies is remote reconnaissance, with one or more onboard sensors transmitting data back to the operator(s) in real time. Typically, a miniature UAV is capable of flying a pre-programmed route autonomously, with manual override as an option. At the conclusion of the mission, the vehicle returns for landing, after which it can be quickly disassembled and stowed until its next use. Thermal imaging extends the utility of miniature UAVs to operations in complete darkness and limited visibility, but historically thermal imagers have been too large and heavy for this application. That changed in 1999 with the introduction of Indigo System's Alpha^TM camera, which established a new class of thermal imaging product termed the infrared "microsensor". Substantially smaller and lighter than any other infrared imaging product available at the time, Alpha^TMwas the first camera that could be readily packaged into the nose of a miniature UAV. Its low power consumption was also a key enabling feature. Building upon the success of Alpha^TM, Indigo then took the microsensor class a step further with its Omega^TM camera, which broke all the records established by Alpha^TM for small size, weight, and power. Omega^TM has been successfully integrated into several miniature UAVs, including AeroVironment's Pointer and Raven, as well as the Snake Eye UAV manufactured by BAI Aerosystems. Aspects of the Omega^TM design that have led to its utility on these and other platforms are described, and future prospects for even smaller microsensors are discussed.

This paper discusses model and algorithms to localize and possibly classify land vehicles with networks of 3-axis magnetometers. An elementary dipolar model of the hull magnetization is first introduced. This model holds true at ranges higher than the typical sizes of the vehicles. The detection range limitation is assessed with respect to the sensor sensitivity and bandwidth and considering typical target sizes. Then, the localization approach is described for different sensors configurations. It is based on the estimation of the dipole location and moment with two different numerical methods. The localization performances are evaluated with a broad set of simulated scenarios. The classification approach is then described. It is based on the estimation of the dimensions of an equivalent ellipsoid. Even though this approach shows promising potential, its applicability is mainly constrained by the possible permanent moment associated with the vehicle hull. In conclusion, a glance is given at magnetic records gathered during the NATO/TG25 experimental campaign.

Development of advanced seismic footstep detection systems for perimeter and zone protection can offer new method for improved homeland security and defense applications. High false alarm rates associated with current seismic security systems has been a formidable obstacle in their widespread adoption. This paper describes a novel method for seismic footstep detection in which false alarms are inhibited and virtually eliminated. In addition, a significant increase in detection range for seismic security systems is also reported. Proprietary software was specifically developed to improve processing of the seismic signals. This software allows one to uniquely analyze over three-dozen signal shape parameters within the detected seismic signal. This novel software enables real time signal analysis, thus effectively offering a more efficient and effective alternative to using trained personnel.

A wide variety of sensors are currently available and used to measure magnetic fields. Fluxgate magnetometers and gradiometers measure the direction and magnitude of magnetic fields. Fluxgates are affordable, rugged, compact and very low-power making them ideal for a variety of sensing applications. Fluxgate magnetometer sensors are manufactured in severl geometries and recently have made significant improvements in noise performance, crossfield tolerance and power utilization.

Magnetic sensors are unaffected by rolling terrain, by vegetation and by weather phenomena, so provide a consistent and predictable performance. Most magnetic tracking algorithms work best for a limited span of closest approach distances between the target and any sensor array node and have specific requirements in terms of the relative node placement. Unlike demonstration fields, where the nodes are carefully manually placed, proposed field deployment methods cannot reliably achieve specific spacings. We propose a novel algorithm that is insensitive to variations in spacing, thereby eliminating the limit on closest approach distances, so that the sensor array can locally adapt the algorithm to the array configuration. This local adaptation also enables scalability for whole-array tracking.

In the event of a Weapons of Mass Destruction (WMD) chemical or radiological release, quick identification of the nature and source of the release can support efforts to warn, protect and evacuate threatened populations downwind; mitigate the release; provide more accurate plume forecasting; and collect critical transient evidence to help identify the perpetrator(s). Although there are systems available to assist in tracking a WMD release and then predicting where a plume may be traveling, there are no reliable systems available to determine the source location of that release. This would typically require the timely deployment of a remote sensing capability, a grid of expendable air samplers, or a surface sampling plan if the plume has dissipated. Each of these typical solutions has major drawbacks (i.e.: excessive cost, technical feasibility, duration to accomplish, etc...). This paper presents data to support the use of existing rapid-response meteorological modeling coupled with existing transport and diffusion modeling along with a prototype cost-effective situational awareness monitor which would reduce the sensor network requirements while still accomplishing the overall mission of having a 95% probability in converging on a source location within 100 meters.

We report on the development and application of an aqueous sensor network (ASN). Designed for operation in lakes or drinking water reservoirs, the immersed ASN nodes are secured in place at a controlled depth by use of anchors with a node to node separation distance of ≤ 20 m. The individual nodes are integrated with various types of sensors enabling measurement of both physical and chemical analyte parameters. Node operation is overseen by programmable microcontrollers; the software on the microcontrollers is structured in a modular format so it can adapt to different types of sensors without extensive reprogramming. Node-to-node communication is achieved using timed bursts to avoid interference from unwanted signal reflections arising from the impedance mismatch at the water-air and water-land interface. We report on the application of the ASN for monitoring temperature and pH throughout a small pool. As desired the individual nodes of the ASN can be integrated with suitable chemical/biological sensors to detect down stream effluents from a source, or to ensure water reservoir quality.

The future battlefield will require an unprecedented level of automation in which soldier-operated autonomous and semi-autonomous ground, air and sea platforms along with mounted and dismounted soldiers will function as a tightly coupled team. Sophisticated robotic platforms with diverse sensor suites will be an integral part of the Objective Force, and must be able to collaborate not only amongst themselves but also with their manned partners. The Army Research Laboratory has developed a robot-based acoustic detection system that will detect and localize on an impulsive noise event, such as a sniper's weapon firing. Additionally, acoustic sensor arrays worn on a soldier's helmet or equipment can enhance his situational awareness and RSTA capabilities. The Land Warrior or Objective Force Warrior body-worn computer can detect tactically significant impulsive signatures from bullets, mortars, artillery, and missiles or spectral signatures from tanks, helicopters, UAVs, and mobile robots. Time-difference-of-arrival techniques can determine a sound's direction of arrival, while head attitude sensors can instantly determine the helmet orientation at time of capture. With precision GPS location of the soldier, along with the locations of other soldiers, robots, or unattended ground sensors that heard the same event, triangulation techniques can produce an accurate location of the target. Data from C-4 explosions and 0.50-Caliber shots shows that both helmet and robot systems can localize on the same event. This provides an awesome capability - mobile robots and soldiers working together on an ever-changing battlespace to detect the enemy and improve the survivability, mobility, and lethality of our future warriors.

Recent advances in wireless communication and microelectronics have enabled the development of low-cost sensor devices leading to interest in large-scale sensor networks for military applications. Sensor networks consist of large numbers of networked sensors that can be dynamically deployed and used for tactical situational awareness. One critical challenge is how to dynamically integrate these sensor networks with information fusion processes to support real-time sensing, exploitation and decision-making in a rich tactical environment. In this paper, we describe our work on an extensible prototype to address the challenge. The prototype and its constituent technologies provide a proof-of-concept that demonstrates several fundamental new approaches for implementing next generation battlefield information systems. Many cutting-edge technologies are used to implement this system, including semantic web, web services, peer-to-peer network and content-based routing. This prototype system is able to dynamically integrate various distributed sensors and multi-level information fusion services into new applications and run them across a distributed network to support different mission goals. Agent technology plays a role in two fundamental ways: resources are described, located and tasked using semantic descriptions based on ontologies and semantic services; tracking, fusion and decision-making logic is implemented using agent objects and semantic descriptions as well.

Energy-efficient tracking of a target using a sensor network has received significant attention in recent research. Our earlier study on energy-quality tradeoffs in target tracking with binary sensors showed that optimal selective activation of sensor nodes based on prediction of the target's trajectory could achieve orders of magnitude savings in the energy expenditure over naive and random activation, while achieving almost the same tracking quality. In this paper, we consider a more realistic sensor model and extend the analysis of activation strategies to account for the presence of noise in sensor measurements. Our results confirm that the best quality of tracking that can be obtained with selective activation depends on the noise level in sensor measurements and that the optimal radius of activation depends on the noise level and the density of deployment. We also show how duty cycling with selective activation can be used to obtain flexible tradeoffs between the energy expenditure and quality of tracking.

Short-range RF propagation models with antenna elements placed at or near the earth's surface often fail to accurately predict path loss. Adequate mathematical models can be developed and validated to ensure deployed communication systems maintain link closure. Specifically, Unattended Ground Sensor (UGS) systems are deployed to be physically undetected, that is, the units are frequently buried with the antenna extended above earth's surface. This paper reviews the physical effects that determine propagation loss and synthesizes a mathematical model to predict this loss. These predictions are compared to real world propagation measurements in both open fields and in dense foliage for ranges up to 500m.

A convergence of technologies is making deployment of unattended ground nanosensors operationally feasible in terms of energy, communications for both arbitrated and self-organizing distributed, collective behaviors. A number of nano communications technologies are already making network-centric systems possible for MicroElectrical Mechanical (MEM) sensor devices today. Similar technologies may make NanoElectrical Mechanical (NEM) sensor devices operationally feasible a few years from now. Just as organizational behaviors of large numbers of nanodevices can derive strategies from social insects and other group-oriented animals, bio-inspired heuristics for threat assessment provide a conceptual approach for successful integration of nanosensors into unattended smart sensor networks. Biological models such as the organization of social insects or the dynamics of immune systems show promise as biologically-inspired paradigms for protecting nanosensor networks for security scene analysis and battlespace awareness. The paradox of nanosensors is that the smaller the device is the more useful it is but the smaller it is the more vulnerable it is to a variety of threats. In other words simpler means networked nanosensors are more likely to fall prey to a wide-range of attacks including jamming, spoofing, Janisserian recruitment, Pied-Piper distraction, as well as typical attacks computer network security. Thus, unattended sensor technologies call for network architectures that include security and countermeasures to provide reliable scene analysis or battlespace awareness information. Such network centric architectures may well draw upon a variety of bio-inspired approaches to safeguard, validate and make sense of large quantities of information.

The networked communications requirements for programs such as Future Combat Systems and others have spawned numerous developments in the area of low profile, low cost, yet high performance transceivers. A primary objective for these next-generation unattended devices is maximum mission life, hence the radios employ not only low power circuit designs, but also power-efficient routing protocols and fast acquisition waveforms to support duty cycling. The network architecture of the systems employing these transceivers is similarly optimized. In numerous scenarios, low power (< 1 watt transmitted output) transceivers compose the local network that interconnects relatively closely spaced nodes, typically front line sensors. A typically higher-powered, and higher data rate transceiver within the network provides the longer link (tens of kilometers) to a Command and Control Station. Operational considerations specific to each system, such as the number of nodes, anticipated traffic volume, latency requirements, forward error correction, encryption, etc., are used to determine the data rate for both the local and long haul links. Additional requirements for low probability of detection, low probability of intercept, and anti-jam protection provide the final input to the process of waveform selection or design. In many cases, unique transceivers are designed to satisfy the requirements for each of the two links. However, judicious trade-offs between the two can yield a single dual-mode device capable of operating in a low power, low rate mode for sensor interoperability while also offering higher layer communications. This paper outlines the design considerations for networked sensor system transceivers and presents performance data for prototype systems.

This paper reports progress in the development of a miniature photovoltaic (PV) arrays consisting of monolithically series connected AlGaAs/GaAs PV cells used in combination with polymeric photoluminescent fibers to recharge batteries of unattended ground sensors (UGS). Outdoor tests of the arrays showed feasibility of this approach. Optimization of the fibers design (material used, diameter, coupling, etc.) is discussed. Better optical matching of the fibers and PV cells was achieved through replacing of GaAs photoactive layers by AlGaAs ones having a higher bandgap.

MesoFuel, Inc. has developed and demonstrated hydrogen generation systems that, when deployed in conjunction with proton exchange membrane (PEM) or solid oxide fuel cell (SOFC) based power systems, can allow extended mission operations for 30 to 60 days at greatly reduced volume and mass from current power supply technologies. This hydrogen generator-fuel cell system can reduce overall power system mass by 55 to 70% over conventional batteries, and in excess of 80% when compared to available hydrogen storage systems when coupled with a fuel cell. Key innovations in microreactor and hydrogen separation membrane design are the enabling features which make possible these much longer run times than can be realized using state-of-the art power generation systems. In addition, the hydrogen generation units can produce either pure hydrogen or a reformate stream from a diverse set of fuels such as light hydrocarbons (methane, propane, butane), heavy hydrocarbons (JP-8, bio-diesel), and ammonia.

In our current military environment, many operations are fought with small, highly mobile reconnaissance and strike forces that must move in and out of hostile terrain, setting up temporary bases and perimeters. As such, today's warfighter has to be well equipped to insure independent operation and survival of small, deployed groups. The use of unattended ground sensors in reconfigurable sensor networks can provide portable perimeter security for such special operations. Since all of the equipment for the missions must be carried by the warfighter, weight is a critical issue. Currently, batteries constitute much of that weight, as batteries are short-lived and unreliable. An alternative power source is required to eliminate the need for carrying multiple replacement batteries to support special operations. Such a battery-free, replenishable, energy management technology has been developed by Ambient Control Systems. Ambient has developed an advanced mid-door photovoltaic technology, which converts light to energy over a wide range of lighting conditions. The energy is then stored in supercapacitors, a highly robust, long-term storage medium. Ambient's advanced energy management technology will power remote sensor and control systems 24 hours/day, 7 days/week for over 20 years, without batteries, providing for ongoing detection, surveillance and other remote operations.

Within the framework of the NATO AC 323 / RTO TG 25 group, relating to advanced concepts of acoustic and seismic technology for military applications, Technical Establishment of Bourges welcomed and organized a joint campaign of experiment intending to demonstrate the interest of a networked unattented ground sensors for vehicles detection and tracking in an area defense context. Having reminded the principle of vehicles tracking, this paper describes the progress of the test campaign and details particularly sensors and participants deployment, the solution of interoperability chosen by the group and the instrumentation used to acquire, network, process and publish in real-time data available during the test: meteorological data, trajectography data and targets detection reports data. Finally, some results of the campaign are presented.

This paper presents different ways to process acoustic data in order to localize targets.Beamforming and the MUSIC high resolution method have been tested for different propagation conditions during a NATO experimental campaign. This campaign,organized by DG /DCE/ETBS,has involved 6 countries in October 2002 in Bourges (France). Different localization methods were used to get the position of moving sources on a 4 kilometres circuit.The I.S.L. (French-German research institute of Saint Louis)has deployed a network of arrays nearby the circuit to test those localization techniques in different propagation conditions (day/night,early morning,...).Variance and mean error of the localization are compared for the different techniques used.

NATO's Task Group (TG-25) on acoustic and seismic sensing is responsible for assessing the potential technologies that can be cooperatively developed and shared within NATO's countries to provide effective, robust and low-cost battlefield sensor systems. The primary applications will be detection and/or classification of ground troops, ground vehicles, airborne vehicles, artillery and sniper. TG-25 has 3 main objectives: (1) to establish acoustic and seismic standards and data exchange procedures, (2) to compare, analyze, exchange, and develop analytical techniques, computational models and signal processing algorithms, and (3) to plan and conduct joint field experiments. In this paper, we discuss participation in the joint NATO field experiment conducted in France in October 2002. The experiment's goal is to demonstrate interoperability of unattended ground sensors from various participating nations. Results of the experiments will be briefed and discussed. Keywords: TG-25, unattended ground sensor, vehicle tracking

Terrain Commander is a fully automated forward observation post that provides the most advanced capability in surveillance and remote situational awareness. The Terrain Commander system was selected by the Australian Government for its NINOX Phase IIB Unattended Ground Sensor Program with the first systems delivered in August of 2002. Terrain Commander offers next generation target detection using multi-spectral peripheral sensors coupled with autonomous day/night image capture and processing. Subsequent intelligence is sent back through satellite communications with unlimited range to a highly sophisticated central monitoring station. The system can "stakeout" remote locations clandestinely for 24 hours a day for months at a time. With its fully integrated SATCOM system, almost any site in the world can be monitored from virtually any other location in the world. Terrain Commander automatically detects and discriminates intruders by precisely cueing its advanced EO subsystem. The system provides target detection capabilities with minimal nuisance alarms combined with the positive visual identification that authorities demand before committing a response. Terrain Commander uses an advanced beamforming acoustic sensor and a distributed array of seismic, magnetic and passive infrared sensors to detect, capture images and accurately track vehicles and personnel. Terrain Commander has a number of emerging military and non-military applications including border control, physical security, homeland defense, force protection and intelligence gathering. This paper reviews the development, capabilities and mission applications of the Terrain Commander system.

A methodology and system is presented for phenomenological research for near and far-field data collection, processing, and analysis of seismic, acoustic, and electromagnetic signatures associated with facilities in operation or under construction. A discussion of sensor selection and positioning considers the signature sources, the background environment, the signal propagation media, and the signal levels of interest. To acquire data of sufficient quality for robust analysis, the Enhanced Field Data Acquisition Logging sensors (EFDALS) system is utilized, providing a rugged and portable, high-fidelity digital recording capability. This system, comprised of a variety of transducers, front-end signal conditioners, digitizers, and digital audio tape recorder, has been integrated with the data reduction, processing, and archiving capabilities developed during seven years of reliable data acquisition.

Counter battery operations have traditionally relied upon weapon locating radar and long range acoustic detection to locate hostile systems, friendly artillery fire is then used to destroy the enemy. At short ranges the timelines are such that this can be achieved, however at longer ranges with extended flight times and reduced out of action times, the 'shoot and scoot' tactics of enemy systems, this process is not effective. This capability can be regained with forward deployed sensors which detect and track the enemy indirect fire systems both during and after firing. This paper explains how netted sensors working co-operatively can solve the system level problems of long range counter battery operations, to ensure that the munition engages the target. Results show that low cost sensors placed close to areas of interest can locate artillery targets with accuracies exceeding current more expensive detection systems. Once the target has been located and identified it may be tracked using the same sensor network. Updating the munition with these details will ensure successful engagement. Results will be shown demonstrating the location capability of a low cost netted sensor system against rockets, mortars and shells.

Smaller numbers of own forces scattered over wide areas and time pressed for solutions demand the availability of highly mobile, rapidly deployable reconnaissance forces that are equipped with advanced surveillance systems. The recce patrols of the armored reconnaissance corps are one element of reconnaissance. The ground sensor equipment BSA^TM (Bodensensorausstattung) will be one of the technical reconnaissance means available to recce patrols. The BSA^TM comprises a set of passive sensors with intelligent evaluation and fusion as well as radio transmission. The BSA^TM consists of several ground sensor units which are positioned in the reconnaissance area, and the receive and display units which, for instance, are integrated in the reconnaissance vehicle. The main tasks of the BSA^TM for surveillance of roads and critical points are the autonomous detection, classification and type-identification of combat and combat support vehicles, the recognition of the direction of movement and speed as well as the determination of the number of vehicles. In a close-in security mode, the BSA^TM is also used to detect and classify personnel. The system and some results are presented as well as the concept for the integration of the sensor reports into a C³-system.

changed substantially and that surveillance systems designed to operate against heavy armor following conventional tactics have to adapt to a “New Threat” environment. This observation is very pertinent to the use of acoustic and seismic sensors. These sensing modalities have been used with success against a threat consisting of armored vehicles powered by large Diesel engines. In the type of conflicts that we are likely to encounter in places like Afghanistan, Yemen and other SE Asian countries, US forces will be faced by a threat that can move about in converted civilian vehicles, Figure 1. Systems like the Wide Area Mine (a.k.a. Hornet) and the Brilliant Anti-Tank Munition (BAT) exploited the loud and distinctive signatures of combat vehicles to direct their fire control system. Other surveillance systems such as Steel Rattler / Steel Eagle and DARPA’s Micro-IUGS focused on “high value targets”, also military vehicles of considerable size. All of these target vehicles are powered by large, noisy diesel engines and have large tires or tracks that produce substantial seismic signatures.The object of this paper is to present an analysis of the signatures of civilian vehicles that may be adapted to military or terrorist activities. We will then look at the sensor configurations that are best adapted to detect and track these vehicles. Some examples of the type of surveillance data that we can obtain are also shown in the paper.

A system architecture, and a hardware implementation leveraging the architecture, has been developed for energy-aware, networked, embedded systems designed for use in tactical unattended ground sensor (UGS) applications. This modular system architecture is designed around a flexible bus design that meets the needs for low-power embedded systems, incorporating support for 32-bit inter-module data transfers, module synchronization, power control, and power distribution. A Linux-based software framework operating on the main system processor has been developed to provide application developers with the ability to easily leverage the hardware functionality of the system. The low-power design methods employed in the system design are discussed along with a system implementation using these methods.

McQ Associates, Inc. has worked on a number of efforts to develop practical, fieldable infrared imaging systems which are intended to be used as an integral part of low power remote sensor and surveillance systems. Recent efforts contributing to such an integrated system have been funded through the Office of Naval Research, the U.S. Army Picatinny Arsenal, and the Air Force Research Lab in Rome, NY. The efforts have culminated in developing a digital signal processor based platform capable of detecting, tracking, and extracting multiple targets within either a 360 degree or fixed field of view. This paper discusses the challenges in the developments of such a sensor, focusing on extending achieving reasonable operating ranges, achieving low power, lowering size and cost, and applications for this technology.

There is a general need for improved detection range and false alarm performance for seismic sensors used for personnel detection. In this paper we describe a novel footstep detection algorithm which was developed and run on seismic footstep data collected at the Aberdeen Proving Ground in December 2000. The initial focus was an assessment of achievable detection range. The conventional approach to footstep detection is to detect transients corresponding to individual footfalls. We feel this is an error-prone approach. Because many real-world signals unrelated to human locomotion look like transients, transient-based footstep detection will inevitably either suffer from high false alarm rates or will be insensitive. Instead, we examined the use of spectrum analysis on envelope-detected seismic signals and have found the general method to be quite promising, not only for detection, but also for discrimination against other types of seismic sources. In particular, gait patterns and their corresponding signatures may help discriminate between human intruders and animals. In the APG data set, mean detection ranges of 64 meters (at P_D=50%) were observed for normal walking, significantly improving on ranges previously reported. For running, mean detection ranges of 84 meters were observed. However, stealthy walking (creeping) remains a considerable problem. Even at short ranges (10 meters), in some cases the detection rate was less than 50%. In future efforts, additional data sets for a range of geologic and environmental conditions should be acquired and analyzed. Improvements to the detection algorithms are possible, including estimation of direction of travel and the number of intruders.

This paper describes a digital-ultrasonic ground network, which forms an unique “unattended mote sensor system” for monitoring the environment, personnel, facilities, vehicles, power generation systems or aircraft in Counter-Terrorism, Force Protection, Prognostic Health Monitoring (PHM) and other ground applications. Unattended wireless smart sensor/tags continuously monitor the environment and provide alerts upon changes or disruptions to the environment. These wireless smart sensor/tags are networked utilizing ultrasonic wireless motes, hybrid RF/Ultrasonic Network Nodes and Base Stations. The network is monitored continuously with a 24/7 remote and secure monitoring system. This system utilizes physical objects such as a vehicle’s structure or a building to provide the media for two way secure communication of key metrics and sensor data and eliminates the “blind spots” that are common in RF solutions because of structural elements of buildings, etc. The digital-ultrasonic sensors have networking capability and a 32-bit identifier, which provide a platform for a robust data acquisition (DAQ) for a large amount of sensors. In addition, the network applies a unique “signature” of the environment by comparing sensor-to-sensor data to pick up on minute changes, which would signal an invasion of unknown elements or signal a potential tampering in equipment or facilities. The system accommodates satellite and other secure network uplinks in either RF or UWB protocols. The wireless sensors can be dispersed by ground or air maneuvers. In addition, the sensors can be incorporated into the structure or surfaces of vehicles, buildings, or clothing of field personnel.

Remote surveillance sensors are expected to play an increasing role in support of battlefield operations of the future. This paper discusses the developments within remote ground sensors, particularly the miniaturisation of these devices such that they could now be deployed and monitored from UAVs.

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