Long duration finite-difference time domain (FDTD) simulations of seismic wave propagation from spatially and time varying sources are necessary to produce synthetic data of ground motion, data that is required for the development of unmanned ground sensor systems, which are the next wave in modern battlefield technology. We have generated data from moving synthetic sources that are typically found in a battlefield scenario, a generic representation of a moving tracked vehicle and a running human. The computational approach and requirements for the long-duration simulation including the geologic model, the moving vehicle force algorithm, the resulting particle velocity wave fields, and example applications of the data are discussed.

A method for the detection and localization of personnel using seismic sensors is described. This particular application of seismic signal processing is different from typical applications involving earthquakes or sonic well-logging, and thus requires the development of new techniques. The proposed approach consists of a matched filter-based detection algorithm, time of arrival association of detected footsteps from different sensors, and localization using a hyperbolic location estimator. This method was tested using data collected in southern New Hampshire from four vertical-axis geophones. The speed of sound at the test site was estimated using an impulsive source. Footsteps were reliably detected at ranges up to 30m. Localization errors were found to vary linearly with range, with an average estimation error of 8.4 m observed. With improvements in the sensitivity of the seismic sensors, this approach will yield reasonable position estimates of personnel for use in a tracking algorithm.

Persons or vehicles moving over ground generate a succession of impacts; these soil disturbances propagate away from the source as seismic waves. These seismic waves are especially useful in detecting footsteps which cannot be detected acoustically. Footstep signals can be distinguished from other seismic sources, such as vehicles or wind noise, by their impulsive nature. Even in noisy environments, statistical measures of the seismic amplitude distribution, such as kurtosis, can be used to identify a footstep. These detection methods can be used even with single component geophones. Moreover, the seismic signal is a vector wave that can be used to track the source bearing. To do such tracking a three-component measurement is needed. If multiple sources are separated in angle, we can use this bearing information to estimate the number of walkers.

It is well known that lines of bearing to an airborne broadband target can be easily measured on a small ground-based array of microphones. With a stationary target and two arrays, the target location can be estimated by direct triangulation, i.e., by the crossing point of bearing lines. With a moving source, however, one must identify arrival times on the arrays that correspond to a common emission point or, equivalently, a common emission time. This paper shows that, with two arrays, the three-dimensional track of a moving airborne target can be determined by finding the stationary points of an iterative non-linear equation. The equation is of the form (tau) _geo((tau) _bt) equals (tau) '_bt where (tau) _geo is the difference in travel times determined from geometry, (tau) _bt is the travel time difference taken from the bearing-time curves for two different arrays, and (tau) _bt is the estimated value for (tau) _bt. The stationary points, i.e., where (tau) _geo equals (tau) _bt, allow the target track to be computed directly from triangulation. Examples are discussed using simulated data.

This paper extends our development of acoustical bearings-only target localization for the case of multiple moving targets. The resulting techniques can be used to locate and track targets traveling through a network of acoustical sensor arrays. Each array computes and transmits multiple direction-of-arrival (DOA) estimates to a central processor, which employs the target localization technique. In previous work, we developed ML techniques that may or may not account for the fact that a bearing measurement points to the location of a moving target at a retarded time. By inserting a simple bearings association computation in the ML methods, we define quasi-ML techniques that can estimate the location and velocity of multiple targets using multiple bearing estimates per a sensor array.

Multiple sensor arrays distributed over a region provide the means for accurate localization of the (x,y) position of a source. When microphone arrays are used to measure aeroacoustic signals from ground vehicles, random fluctuations in the air lead to frequency-selective coherence of the signals that arrive at widely-separated arrays. We have shown previously that even in cases of imperfect spatial coherence, improvements in source localization accuracy are possible when the data from widely-separated arrays are processed jointly by a fusion center. Further, we have shown that a distributed processing scheme involving bearing estimation at individual arrays and time-delay estimation (TDE) between pairs of widely-separated sensors performs nearly as well as the optimum scheme, with significantly lower communication bandwidth. These results were obtained by studying the Cramer-Rao bound (CRB) on source localization accuracy based on a statistical model for the data measured at the sensors. Refined bounds (Ziv-Zakai) are presented in this paper that imply a threshold value of coherence is needed to achieve accurate TDE between widely-separated sensors. The threshold coherence is a function of the signal to noise ratio, fractional bandwidth, and time-bandwidth product of the observed signals. Results are presented from measured aeroacoustic data that illustrate TDE with widely-separated sensors.

As commercial operating systems such as Microsoft Windows move from the desktop to the embedded world and low-power, low-cost embedded CPU performance increases the distinction between dedicated embedded systems and laboratory demonstration systems is blurring. Signalscape, Inc. has developed a highly flexible acoustic signal processing system with real-time performance on Pentium II class desktop computers running Microsoft Windows. In a recently awarded DARPA program, Rockwell Science Center, Signalscape, and their partners are moving the flexibility and capabilities of Signalscape's many tool kits onto low-cost, low-power systems for unattended sensor applications. In this paper we discuss the results of the first demonstrations of acoustic beamforming using a small network of sensors.

Starting in the early 1990's, uncooled microbolometer thermal imaging sensor technology began to move out of the basic development laboratories of the Honeywell Corporation in Minneapolis and into applied development at several companies which have licensed the basic technology. Now, this technology is addressing military, government, and commercial applications in the real world. Today, thousands of uncooled microbolometer thermal imaging sensors are being produced and sold annually. At the same time, applied research and development on the technology continues at an unabated pace. These research and development efforts have two primary goals: 1) improving sensor performance in terms of increased resolution and greater thermal sensitivity and 2) reducing sensor cost. Success is being achieved in both areas. In this paper we will describe advances in uncooled microbolometer thermal imaging sensor technology as they apply to the modern battlefield and to unattended ground sensor applications in particular. Improvements in sensor performance include: a) reduced size, b) increased spatial resolution, c) increased thermal sensitivity, d) reduced electrical power, and e) reduced weight. For battlefield applications, unattended sensors are used not only in fixed ground locations, but also on a variety of moving platforms, including remotely operated ground vehicles, as well as Micro and Miniature Aerial Vehicles. The use of uncooled microbolometer thermal imaging sensors on these platforms will be discussed, and the results from simulations, of an uncooled microbolometer sensor flying on a Micro Aerial Vehicle will be presented. Finally, we will describe microbolometer technology advancements currently being made or planned at BAE SYSTEMS. Where possible, examples of actual improvements, in the form of real imagery and/or actual performance measurements, will be provided.

Amorphous silicon (a-Si) microbolometer technology is a silicon fab-compatible uncooled detector technology which offers a low cost, high volume approach for infrared sensor and imager applications. Raytheon has used this detector technology to develop a 160x120 a-Si based infrared camera. The systems goal was to develop an affordable infrared imaging product that provides acceptable performance for many commercial and military applications. To meet low power goals, a non-temperature controlled detector approach was required. This led to the challenge of developing a technique for operating over ambient temperature that includes correction techniques that account for offset and responsivity non-uniformities over ambient operating temperature. This paper describes the operating performance parameters of a typical a-Si 160 X 120 IR camera. This camera is currently entering production, and will be produced by the Raytheon Commercial Infrared business.

Raytheon Electronic Systems is under contract from the DARPA Advanced Technology Office to design, fabricate and deliver the Modular Miniature Imaging Sensor (M²IS) incorporating a Er:glass eyesafe laser rangefinder. The M²IS is a rifle-mounted system that integrates a high- performance multispectral sensor with an eyesafe laser rangefinder and a digital compass. Dual FOV reflective optics provide capability to acquire and identify targets at ranges of several kilometers. The LRF and compass facilitate hand-off to remote fire power. M²IS provides the soldier an integrated surveillance, targeting, and fire control system that consumes less than 6.5 W and weighs less than 7.5 lbs. This paper reviews field data acquired with the first deliverable sensor and compares measured performance with previously acquired laboratory test data. Projections for improvements with a higher power laser, planned for incorporation in the second deliverable sensor, are summarized.

Amherst Systems is developing low-power, reconfigurable sensors that reduce video bandwidth but maintain high resolution in real-time surveillance, targeting, and precision strike applications. Our Dynamically Reconfigurable Vision (DRV) technology, through on-chip multiple windowing, seeks to reduce the amount of irrelevant spectral information that is collected, and thus make more effective use of available bandwidth than is possible with conventional imaging technology. Minimization of irrelevant data in the video processing chain reduces processing requirements and allows communication of more information in real-time over bandwidth-limited channels. This leads to a reduction in unit power consumption, complexity, size, and cost. Here we present an experiment that integrated our prototype DRV camera and omnidirectional optics supplied by the Canadian Defence Research Establishment Suffield.

New opportunities for battlefield surveillance and modeling are unfolding with the advent of smart sensors linked via digital wireless networks. One exciting prospect is the use of tomographic techniques in order to create real-time three-dimensional modeling and analysis of the environment that is immediately accessible to battlefield forces. We have developed a small-scale ground sensor network for this application. We discuss initial deployment of this network as a tracking system.

The development of magnetic sensors for the detection, localization, and classification of time-critical targets is of great importance in monitoring, surveillance, intelligence, and security applications. This is particularly true for the military where precision targeting of armed enemy troops, tracked and wheeled vehicles requires timely updates of their movements. To address this need, Quantum Magnetics (QM) is developing small, low power, low cost magnetic sensor modules, and high performance digital electronics that can be used to passively detect magnetic anomalies in the battlefield generated by the presence and movement of armed troops and military vehicles. The focus is on Magneto-Resistive (MR) sensors that can be fabricated by microelectronics techniques. These sensors represent a mature technology and are widely available commercially. They operate at room temperature with high sensitivity and have a broad bandwidth. The long-term vision is to integrate these modules into a network of battlefield microsensors that include a variety of other sensing technologies (acoustic, seismic, IR, etc.). We will discuss MR system design considerations and results obtained in recent field tests. A highly sensitive magnetic sensor module would also find numerous applications in security operations and surveillance of perimeters and borders, landmine/UXO detection, and detection of concealed weapons.

Micro Unattended Ground Sensor Networks will likely employ magnetic sensors, primarily for discrimination of objects as opposed to initial detection. These magnetic sensors, then, must fit within very small cost, size, and power budgets to be compatible with the envisioned sensor suites. Also, a high degree of sensitivity is required to minimize the number of sensor cells required to survey a given area in the field. Solid state magnetoresistive sensors, with their low cost, small size, and ease of integration, are excellent candidates for these applications assuming that their power and sensitivity performance are acceptable. SDT devices have been fabricated into prototype magnetic field sensors suitable for use in micro unattended ground sensor networks. They are housed in tiny SOIC 8-pin packages and mounted on a circuit board with required voltage regulation, signal amplification and conditioning, and sensor control and communications functions. The best sensitivity results to date are 289 pT/rt. Hz at 1 Hz, and and 7 pT/rt. Hz at f > 10 kHz. Expected near term improvements in performance would bring these levels to approximately 10 pT/rt Hz at 1 Hz and approximately 1 pT/rt. Hz at > 1 kHz.

The sensor community has long been presented with the problem of prioritizing among several competing sensor system variables due to the inability to produce a high confidence, low-cost, reliable, and compact device. Typically a solution for very critical scenarios has been a high-cost scale reduction of larger more laboratory based instrumentation. This often produces data on a single parameter that is beyond reproach, however this can also produce a very delicate, bulky, and costly system often requiring a vacuum system or some sort. An alternative approach involves using micro-electro-mechanical systems based sensors.

Nanocrystalline porous silicon films (nanodots) and polymeric silicon wires (nanowires) have been used to detect chemicals in gas and liquid phase. Transduction mechanisms using quantum confinement derived photoluminescence and optical reflectivity have been used. Photoluminescence intensity is modulated by energy or electron transfer induced quenching, and a shift of the Fabry-Perot reflectivity fringes from thin nanocrystalline films occurs upon molecular absorption. Examples of irreversible detection and reversible sensing modes for explosives, nerve warfare agents, and various odors of commercial interest will be provided. A catalyst can be incorporated into the nanomaterials to provide specificity for the analyte of interest.

The current trend to develop low cost, miniature unattended ground sensors will enable a cost-effective, covert means for surveillance in both urban and remote border areas. Whereas the functionality (e.g., sensing range and life in the field) of smaller UGS may be limited due to size and cost constraints, a network of these sensors working cooperatively together can provide an effective surveillance capability. A key factor is the ability of these sensors to work cooperatively to achieve a `collective' functionality that can meet the surveillance objective.

The Defence Research Establishment Valcartier has initiated in 1998 R&D work to investigate and to demonstrate key technologies required for future Defensive Aid Suite to protect Light Armoured Vehicles. A basic Defensive Aid Suite demonstrator (Phase I) was built and integrated into the LAV vetronics by Litton Systems Canada and his consortium. The Defensive Aid Suite consisted of a 2-band HARLID^TM-based laser detection head, a processor capable to control and deploy countermeasures and a DAS touch-screen display all integrated in a Light Armored Vehicle. The crew was able to select the operation mode for direct fire or smoke deployment by pushing one of the pair of buttons available at the bottom of the display. This system was successfully demonstrated in October 1999 during an international trial. This article gives an overview of the results obtained in the field as well as some of the lessons learnt. It also describes laboratory and field measurements made on the Laser Warning Receiver unit itself. The results of the DAS tactical use and of Human factor evaluation will illustrate its performance within typical laser threat scenarios. This work will serve as the basis for the recommendation of a future DAS demonstrator (Phase II) integrating more sensors and countermeasures.

We describe test results using the FIRST (Fast InfraRed Sniper Tracker) to detect, track, and range to bullets in flight for determining the location of the bullet launch point. The technology developed for the FIRST system can be used to provide detection and accurate 3D track data for other small threat objects including rockets, mortars, and artillery in addition to bullets. We discuss the radiometry and detection range for these objects, and discuss the trade-offs involved in design of the very fast optical system for acquisition, tracking, and ranging of these targets.

The operational lifetime of an Unattended Ground Sensor (UGS) depends on the power consumption of the package and the space allocated for batteries. Solar cells have the potential of dramatically increasing operational lifetimes of UGS instruments by providing supplemental power, but in this application solar cells are subject to a number of non-traditional constraints. There are UGS applications where the solar array will need to be covert or have a high shock resistance. It is also possible that a UGS-solar array will be placed in a shaded area or randomly oriented with respect to the path of the sun. This paper will first survey conventional approaches towards solar battery charging and then discuss non-conventional approaches applicable to randomly oriented and covert UGS solar cell arrays.

The force that is able to obtain the greatest amount of information will dominate tomorrow's battlefields. Although battlefield situation information can come from a number of sources, one particularly important segment of intelligence gathering is aerial surveillance. For the small, lightly armed unit in the field, the location and force structure of local enemy troops is critically important. Systems Planning and Analysis has conceived and performed a preliminary analysis of a low-cost, lighter-than-air surveillance system. The preliminary analysis includes the concept definition, a detailed trade study to determine the optimal configuration of the surveillance system, high-pressure inflation tests, and a control analysis. This paper will provide the details in these areas of the design and provide an insight into the feasibility of such a system.

A system has been developed for delivering and attaching a sensor payload to a target using a standard 40-mm grenade launcher. The projectile incorporates an attachment mechanism, a shock mitigation system, a power source, and a video-bandwidth transmitter. Impact and launch g-loads have been limited to less than 10,000 g's, enabling sensor payloads to be assembled using Commercial Off-The-Shelf components. The GLIMPS projectile is intended to be a general-purpose delivery system for a variety of sensor payloads under the Unattended Ground Sensors program. Test results and development issues are presented.

Accurate Automation Corporation has completed the conceptual design of a mortar launched air vehicle system to perform close range or over-the-horizon surveillance missions. Law enforcement and military units require an organic capability to obtain real time intelligence information of time critical targets. Our design will permit law enforcement to detect, classify, locate and track these time critical targets. The surveillance system is a simple, unmanned fixed-winged aircraft deployed via a conventional mortar tube. The aircraft's flight surfaces are deployed following mortar launch to permit maximum range and time over target. The aircraft and sensor system are field retrievable. The aircraft can be configured with an engine to permit extended time over target or range. The aircraft has an integrated surveillance sensor system; a programmable CMOS sensor array. The integrated RF transmitter is capable of down- linking real-time video over line-of-sight distances exceeding 10 kilometers. The major benefit of the modular design is the ability to provide surveillance or tracking quickly at a low cost. Vehicle operational radius and sensor field coverage as well as design trade results of vehicle range and endurance performance and payload capacity at operational range are presented for various mortar configurations.

This paper examines the use of arrays of seismic sensors to enhance signals where multiple sources and an inhomogeneous medium complicate the received signal. Array processing is useful because it offers the opportunity to enhance SNR of the target signal while attenuating noise sources via spatiotemporal filtering. We used an adaptive beamforming algorithm to isolate the particular signal of interest from ambient noise and an interferer. The unpredictable nature of the noise and interferer environment was addressed by having the beamformer adapt to the environment. We present the results of using the beamformer on data from a thirty- geophone array. Initial results indicate inhomogeneities in the vacinity of the seismic sensors caused the significant perturbations to the wavefront. The adaptive algorithm was able to compensate for this and thereby performed better than the traditional delay-and-sum algorithm at isolating the target signal from the interfering signals.

A new approach to Automatic Target Recognition and unmanned navigation based on sensor fusion, theory of catastrophes, and real-time processing is described.