the integration of multiple sensors for the purpose of forming a Single Integrated Air Picture (SIAP) is currently being intensely investigated. There are only a few existing techniques that enable SIAP development. Assuming there are no sensor biases and communication latencies, the ideal picture can be formed when all the sensor information is available at each network node. The target state vectors for each picture are identical when they are generated using the same time-ordered data and algorithms. However, this is impractical in a tactical environment and several techniques, such as conventional filtering, optimal track and hybrid fusion, and tracklets, have been proposed to form the SIAP with a reduced amount of data. A combination of techniques will be needed since no single one has the ability to adequately form the picture. The estimation techniques can also be employed to perform sensor alignment. Alignment is the foundation by which the SIAP can be constructed. This paper presents track fusion and tracklet techniques for the purpose of performing target tracking and sensor alignment. Simulation results will be used to illustrate the performance of the estimation techniques.

An analytic solution for the fusion of track estimates produced from two asynchronous measurements has been recently developed. The fusion process can occur at any time in the interval between the arrival of the second measurement of a fusion interval and the first measurement of the next fusion interval. The solution was stipulated to be a weighted sum of the previous fused estimate and the two individual estimates. The matrix weights are the unknowns for which a solution was formulated. This fusion process has properties that are identical to the Kalman filter. Even though this technique is a breakthrough, it is restricted to the fusion of only two estimates. The objective of this paper is to provide a numeric solution to this track fusion problem with an arbitrary number of asynchronous measurements. Simulation results will be employed to compare the performance of the Kalman filter and the track fusion algorithm in a multisensor environment.

Modern command and control systems depend on surveillance subsystems to form an overall tactical pictures. The use of sensors with different capabilities can improve the quality of the aggregate picture. However, the quality of the fused data is highly dependent on the quality of the data that is supplied to the fusion processor. Before the fusion process takes place, sensor data has to be transformed to a common reference frame. Since each individual sensor's data may be biased, a prerequisite for successful data fusion is the removal of the bias errors contained in the data from all contributing sensors. In this paper, a technique is developed to perform absolute sensor alignment (the removal of bias errors) using information from moving objects, such as low earth orbit satellites, that obey Kepler's laws of motion.

Practical application of multi-sensor fusion is critically dependent on the sensor system's registration in both time and space. A UK MOD study involving both Government agencies and industry has explored the practical issues of the field deployment of radar and EO (IRST) sensors and the subsequent fusion of their output data at both the track and plot level. The program used commercially available GPS units as the time and position sensor on both radar and EO sensors. The same system was used to record target position. The paper will use the data collected during the practical field trials to illustrate the impact of time and positional errors on the fusion process.

The purpose of this paper is to describe an experimental procedure for verifying the navigation data provided by the NASA Goddard Space time Flight Center's Tropical Rainfall Measurement Mission (TRMM) Precipitation Radar (PR). The TRMM PR is a satellite-borne, electronically scanning, range-gated radar that produces 3D images of the structure of atmospheric precipitation. Due to the dynamic nature of precipitation events in space and time, proper collocation is critical to the accuracy of the data.11

A methodology for determining absolute inertial angular orientation of a spinning body is demonstrated utilizing independent angular measurements for two arbitrary body- fixed sensor systems. A particular application is denoted utilizing Army Research Laboratory Solar Likeness Indicating Transducers and magnetoresistive sensors which provide body- fixed, independent angular measurements with regard to their respective local fields. Knowledge of the local field orientations and a coordinate transformation provide the inertial orientation angles, commonly called psi and theta, useful for evaluation and development of advanced flight bodies and as a navigation aid for brilliant munitions. The device is called POINTER: Projectile Orientation In Navigation TERms for a spinning body containing optical and magnetic sensors. Typical sensor data and reduction processes are reviewed and alternative field measurements are discussed.

Accurate measurement of angular motions of spinning bodies with on-board sensors has long been recognized as a daunting task. Recent advances in magnetic sensor technologies have yielded devices small enough, rugged enough, and sensitive enough to be useful in systems making high-speed, high- resolution measurements of attitude relative to magnetic fields when installed on free-flying bodies. Such a measurement system, called a `MAGSONDE' (MAGnetic SONDE), has been designed for use in spinning projectiles for the estimation of in-flight angular orientation with respect to the earth's magnetic field.

This paper presents experimental results using a ZnSe Risley prism scanner in which diffractive gratings were etched into the prism faces to correct for chromatic aberrations. Risley prism scanners, which consist of independently rotating prisms, offer distinct advantages over mirrored systems. The faces of the two scanner elements are parallel and adjacent to one another, resulting in a simple, lightweight, and compact system with extremely high pointing stability and accuracy. Laboratory results for the scanner, when used in a midwave infrared imaging system, demonstrated a total field of view +/- 22.5 degrees with almost no aberrations. The optical performance of the scanner demonstrated a factor of two improvement in resolution when compared to an equivalent scanner using no diffractive correction. We conclude that the use of diffractively corrected prisms offer a new potential for using Risley prisms as a alternative lightweight scanner in missile seekers.

This paper presents a miniature pan/tilt pointing mechanism designed to point small sensors and other payloads anywhere within a +/- 45 degree(s) range at high speeds. Unlike other pan/tilt actuators, which predominantly use a motor-on-motor design to achieve two degrees of freedom motion, this device has only one moving part mounted on a ring-in-ring gimbal that is driven by a single 2D motor. Angular positioning of the payload, which is attached to the front side of the gimbal, is achieved by the interaction between a high energy samarium cobalt magnet, mounted on the back side of the gimbal, and the fields produced by four stationary coils. The coils are arranged on the sides of a pyramid structure that encloses the magnet and gives the payload an unobstructed 180 degree(s) field of view. This scheme allows the device to be much smaller, lighter, and inherently more efficient than traditional motor-on-motor pointing mechanisms. Miniature, non-contacting capacitive angular position sensors are integrated into each of the two axes to provide instantaneous position feedback to a controller. The magnetic and mechanical design of the device will be discussed along with the derivation of the various transfer equations and control laws. Open-loop performance data will also be presented.

This work presents a method for missile autopilot design in the presence of actuator and uncertain dynamics. Nonlinear control algorithms are derived based on both missile aerodynamics and actuator dynamics. To account for system nonlinearities and uncertainties due to varying flight conditions, a memory-based compensation unit is developed and integrated into the strategy. Simulation on EMRAAT missile validates the effectiveness of the proposed control method.

Current ground-based tracking systems at Air Force test and tracking ranges require transmission of a variety of signals from rotating platform to fixed control center. At the moment, the task of signal rotating-to-fixed (RTF) transmission is exclusively handled by cable wrap structures, which provide small angular range, low speed, and are inconvenient to use. To solve this problem. Physical Optics Corporation has investigated an advanced electro- optic hybrid rotary joint (EOHRJ) technology for multiple channel RTF signal transmission. The developed EOHRJ provides the following features. First, it includes a unique two-layer electrical sip ring. This ring is able to accommodate hundreds of transmission channels, including electrical power, control, feedback, and low speed data signals. Second, it uses a unique optical fiber slip ring. This ring, by incorporating electrical time division multiplexing and optical wavelength division multiplexing technologies, is able to provide multiple channel, high data rate (over GBPS), and bi-directional signal transmission. Third, the three-layer overlapped EOHRJ, meets particular military application demands and is designed to be reliable for operation in harsh environments operation, adaptive to stringent size requirements, and accommodating to electrical and mechanical interfaces of current tracker systems.

This work addresses the problem faced by an aircraft that is off its nominal flight path. The goal is to find the optimal trajectory to safely and efficiently return the aircraft to its proper path in rugged terrain. The authors approach to this problem is to consider the space of possible trajectories as a series of linked maneuvers, so that a particular trajectory can be described by the ordered list of parameters specifying the maneuvers. A penalty function is minimized with respect to variations of the maneuver parameter list. The work considered trajectories of up to three straight flight segments linked by turns. The penalty function includes terms penalizing elapsed time for the measure, distance climbed, and closest approach to the ground as well as distance from the nominal flight path at the end of the maneuver. Minimization is performed by means of an adaptive fuzzy-logic-enhanced genetic algorithm.

Technological breakthroughs in the field of imaging sensors for missile-seekers and related signal processors helped the military users to achieve `force multiplication'. Fourth generation missile seekers use millimeter-wave and/or infrared-imaging technologies to benefit from the high- resolution capabilities to home on a selected aim-point on a given target using multi-mode signal processing. The drive behind such technologies is to get a first-pass mission- success against the target.

Most greylevel threshold-selection algorithms find thresholds that are optimal according to specific regional or global statistics. These traditional approaches do not involve any model of the target except that it is expected to be separable from the background by a threshold suite. Thus, they fail to make use of the most important feature of imaging target trackers: the well-known location of the target in each frame. We present a technique that uses knowledge of the target location to build up a temporally- smoothed greylevel distribution map from which we extract two thresholds that separate from the background the greylevels with a high probability of belonging to the target under track.

This paper discuses a simulation approach that has streamlined the real-time software development process for a closed loop image-based tracking system. The MATLAB/SIMULINK simulation consists of elements constructed from common source modules shared with the deliverable system. The simulation has provided a tool to support algorithm development for the fundamental system components, including a system controller, a servo controller, and an image processor. In addition, the simulation has provided a testbed for verification of system performance. The context for this application is the low rate initial production phase of a tactical airborne avionics system that includes an image-based tracking system.

This paper presents a prototype Dynamically Reconfigurable Vision (DRV) system. DRV is based on the intelligent, dynamic allocation of spatial and temporal resources in order to maximize system performance. Minimization of irrelevant data in the video processing chain reduces on- board processing requirements, power consumption, and payload, and increases the amount of relevant information that can be communicated over bandwidth-limited channels. Our DRV system employs a real-time reconfigurable CMOS image sensor which supports multiple variance-resolution, independently-configurable windows per exposure, operates in a snapshot capture mode to minimize smear, and outputs data through multiple video ports to minimize readout time. Multiple, time-correlated windows enable the vision system to better support multiple targeting functions concurrently, and achieve a maximum level of situational awareness. This imager is capable of reconfiguring itself in microseconds upon demand; frame-by-frame configurable parameters include frame rate, integration time, and parameters defining the position, shape, size, and resolution of each window. The system additionally features a small footprint and very low power, resulting from a CMOS implementation and on-chip signal processing using passive circuitry. The advantages of DRV over conventional imaging techniques are discussed, and the overall design and performance of our DRV sensor and camera are presented.

Automatic target detection and tracking for an infrared imaging seeker is a complex topic. The IR sensor images are processed in real time to detect and discriminate the targets in the seeker's field of view. A multitude of image processing and target discrimination algorithms can be implemented in the seeker. The complexity of these algorithms must take into account the potential processing limitation of the seeker on-board processor. Tunable band- pass spatial filters have been considered to optimize the target detection in the input image of the seeker. The spatial frequency features are extracted from the target which is selected by the tracking algorithm. The center spatial frequency of the filter is then automatically tuned to that of the target. Various techniques to derive 2D tunable band-pass filters are presented in this paper. The convolution windows must be characterized by a limited size for real-time application. The sensitivity of the filters to an amplitude threshold variation int he target detection will be evaluated.

Air-to-Air Homing Missile has widely adopted infrared seeker, which makes use of thermal energy emitted from the target to detect it exactly. The target is equipped with countermeasure (CM) such as flare to protect itself from homing missile. The purpose of this paper is to develop counter-countermeasure (CCM) to cope with the CM operated by the target. Not only the radiant features of the target but also that of the flare at ultraviolet band have been compared and analyzed to select the band that can effectively remove the effects of the flare. We use a reference level for removal of the noise effects and the background. The simulation results show that our CCM algorithm can detect precisely the target location in spite of the presence of the flare.

Temporal profiles of point-like dim targets and the extended cloud pixels provide useful information in detecting the target. Among the recent methods that utilize temporal profile of pixel in detecting point target are Triple Temporal Filter (TTF) and Continuous Wavelet Transform (CWT). TTF uses two damped sinusoidal filters, an exponential averaging filter with six appropriate coefficients to deal with different aspects of clutter. TTF is recursive and efficient in detecting point targets without applying any threshold techniques. The performance of CWT is comparable to TTF but all the frames in a sequence need to be stored. Therefore it is computationally complex algorithm.

This paper presents the most up-to-date experimental results obtained during the integration of a 3D Laser Scanner Tracking System and the current Space Vision System used by NASA. Half scale models of modules of the Space Station Freedom have been built for this demonstration and comparison between the current method using video cameras and the Laser Scanner System are presented. The variable resolution laser scanner can track, in real time, targets and geometrical features of an object. The Laser Scanner System uses two high-speed galvanometers and a collimated laser beam to address individual targets on the object. Very high-resolution images and excellent tracking accuracy are obtained using Lissajous figures that provide high pointing accuracy of a laser beam. The prototype automatically searches and tracks, in 3D, targets attached to the object. The locations of the centroid of the detected targets are fed directly into the existing photosolution and attitude control modules of the Space Vision System.

Physical Optics Corporation has developed an automatic polarization sensitive multispectral imaging system for real-time object-to-background contrast enhancement. This system is built around an acousto-optic tunable filter and liquid crystal achromatic rotator of light polarization.

A counter-countermeasures (CCM) algorithm in a target tracking system is required for efficient target tracking under countermeasures (CM) such as infrared flares. Most of the CCM algorithms employ some forms of spectral band discrimination to distinguish between a target and CM. We adopt two detection bands based on the spectral distribution characteristics (SDC) of a target and flares and define the energy ratio between the two band signals (MNR) to represent their SDC and to distinguish them. The proposed algorithm computes the MNR of the incident band signals and its histogram, detects the MNR of flare signal from the histogram, and extracts target signal only from the target and flare mixed signal. To estimate the performance of the proposed algorithm, we simulate it under various conditions. The simulation results show that the proposed algorithm can eliminate the effect of CM well.

Space-based laser communication (LASERCOM) requires precision tracking and pointing in the microradian range. However, the angular vibrations of a satellite platform may be of the magnitude of milliradian and the frequency of 100 Hz or higher. For rejection of the platform vibrations there are two ways: line-of-sight stabilization technology or a fine steering mirror (control system with high closed-loop bandwidth. The former is much more complex in structure and difficult in implement than the latter. So, the latter is always adopted in actual space optical communication engineering. This paper describes a linear quadratic (LQ) optimal controller based on modern control theory for FSM system. Compared with classical controller, the proposed LQ has several advantages: (1) the LQ controller widens the system's closed loop bandwidth; (2) the large improvement in the system dynamic performance; (3) the significant improvement of the system rejection capability on high frequencies disturbance. The FSM system with the LQ controller have been designed and tested. The results confirm the advantages of the LQ controller above and show that it is an efficient control approach for FSM system in LASERCOM.

This paper describes the angular error of the tracking antenna system for LEO (Low Earth Orbit) satellite through the alignment experiment. The purpose of this alignment experiment is to reduce the angular error due to the structural alignment and the monopulse null point alignment error. The angular error that can occur during installation on-site, is the key performance parameter of the tracking antenna system. The angular error is analyzed via a simulation and boresight measurement. The simulation is done with formulas to be derived from vector concept for 3-axis movement. The formulas of the structural alignment are verified by comparing the formula result with the field measurement. Also, the angular error due to monopulse null shift is obtained via boresight measurement. The calibration results for both alignments are described.

The application in image and signal processing, for programmable devices such as EPLDs and FPGAs combined with high volume components developed for the TV set top box and PC markets, can provide a flexible solution where a number of conflicting requirements exist. The mix of technologies provides the designer with potentially higher performance at lower cost and size over DSP or RISC processor solutions for the rugged environment market applications.

Optical platforms increasingly require attitude knowledge and optical instrument pointing at sub-microradian accuracy. No low-cost commercial system exists to provide this level of accuracy for guidance, navigation, and control. The need for small, inexpensive inertial sensors, which may be employed in pointing control systems that are required to satisfy angular line-of-sight stabilization jitter error budgets to levels of 1-3 microradian rms and less, has existed for at least two decades. Innovations and evolutions in small, low-noise inertial angular motion sensor technology and advances in the applications of the global positioning system have converged to allow improvement in acquisition, tracking and pointing solutions for a wide variety of payloads. We are developing a small, inexpensive, and high-performance inertial attitude reference system that uses our innovative magnetohydrodynamic angular rate sensor technology.