A 1995 vision statement for Air Force Modeling and Simulation (M&S) highlighted the need for a Joint Synthetic Battlespace (JSB); an environment wherein warfighters could train and exercise on their real-world equipment while immersed in a realistic contingency or wartime environment. This paper describes our efforts to develop a Joint Synthetic Battlespace for Research and Development (JSB-RD), which will provide a realistic environment within which technologies being developed at AFRL's Information Directorate can be analyzed and tested. Where possible, this environment will attach to operational systems in order to provide military realism that will ultimately improve and shorten the tech transition process. This reconfigurable testbed will provide scalability and evolve over time building upon previous federations, attaching to other federations, while incorporating lessons learned along the way.
This paper attempts to address current issues as they pertain to planning tools used to support the allocation of resources over time in a battlespace environment. It is aimed at developing a mathematical foundation for planning tools that more accurately depict the future unfolding of a dynamic battlespace. It demonstrates that, when the planning process is formulated as an optimal control problem, the requirements for an embedded prediction system become clear and distinct.
This paper introduces the concept of using simulation for both plan tracking and state estimation and prediction. Given some set of objectives the military commander must devise a sequence of actions that transform the current state to the desired one. The desire to do this in faster than real-time so that many courses of action can be considered motivates us to investigate modeling techniques that explicitly produce such courses of action. This class of problem can be modeled as a Markov decision process (MDP) whose principal solution is stochastic dynamic programming. In this paper we consider the extension of a MDP model of air operations to the partially observed case.
This paper discusses the use of modern control theoretic approaches in military command and control. The military enterprise is a highly dynamic and nonlinear environment. The desire on the part of military commanders to operate at faster operational tempos while still maintaining a stable and robust system, naturally leads to the consideration of a control theoretic approach to providing decision aids. I will present a brief history of the science of command and control of military forces and discuss how modern control theory might be applied to air operations.
High data rates of laser communication systems must be complemented by high tracking bandwidth of acousto-optic beam steering technology utilizing Bragg cells. This research investigates applications of advanced control techniques to enhance characteristics of a laser beam steering system containing a Bragg cell - quadrant detector combination. Laboratory characterization of both devices resulting in detailed mathematical description and simulation models is presented. An adaptive model reference controller is designed and validated by computer simulation.
High data rate of laser communication systems should be matched by wide operational bandwidth of beam positioning. This could be achieved by the application of non-mechanical beam steering technologies utilizing acousto-optic phenomena. Major components of acousto-optic beam steering systems, a Bragg cell and a quadrant detector, are subjected to comprehensive laboratory testing and characterization as components of a control system. Mathematical and computer simulation model of the entire steering system, addressing system dynamics, cross-coupling of azimuth and elevation channels, and nonlinearity, and facilitating synthesis of advanced control laws, is developed.
A successful controller design is crucial for establishing and maintaining an optical link between free-space communication stations engaged in a laser communication session. This task is quite difficult due to nonlinear behavior, cross-coupled dynamics, and time-varying characteristics of all known beam steering technologies. A novel adaptive control technique utilizing Lyapunov function to ensure global asymptotic stability of the system, thus resulting in a highly robust system performance, is developed. The technique applied to a piezo-electric mirror setup results in a highly efficient controller design that does not require prior knowledge of system dynamics, while providing independent access to azimuth and elevation positions of the laser beam. The paper presents the basic algorithm and demonstrates the results of its application.
We proposed the use of model reference control for the improvement in the performance characteristics of fine tracking mirrors. We present both analog and digital implementations of model reference control on a specially designed high bandwidth steering mirror and a commercially available lower bandwidth mirror. Improvement in system response and immunity to environmental jitter are demonstrated.
KEYWORDS: Satellites, Acquisition tracking and pointing, Telecommunications, Sensors, Signal processing, Laser communications, Laser systems engineering, Satellite communications, Mirrors, Digital signal processing
Satellite jitter adversely affects the pointing, acquisition, and tracking (PAT) functions of an intersatellite laser communication system. Reliable aircraft-based testing of PAT systems requires that the detrimental effects of aircraft jitter be controlled and a realistic satellite jitter environment be emulated. A novel jitter rejection technique, the self-tuning feed-forward compensation scheme, is developed to minimize the effects of aircraft vibration on the PAT terminal. The self-tuning results in the implicit characterization of the mechanical jitter propagation path, thus facilitating the injection of prerecorded satellite jitter in the control circuitry of steering mirrors.
Fine steering mirrors of satellite-based laser communication systems operate at high frequencies. Performance of such mirrors are adversely affected by bending modes of their moving parts. Application of feedforward compensation of bending modes, resulting in a model reference control scheme, is considered for 5 KHz and 500 Hz optical mirrors.
An active jitter compensation scheme intended for free space intersatellite laser communication, utilizing self-tuning feedforward compensation, is developed. It is implemented via computer-controlled analog circuitry. The theory, design and implementation of the laboratory prototype are discussed. A performance evaluation, comparing the feedforward compensator to existing closed loop control, is presented with the feedforward technique demonstrating significant jitter reduction.
Satellite laser communications offers the potential for lightweight, high speed data transfer. One of the critical aspects of such a system are small, lightweight, high power laser sources. We will evaluate the applicability of SDL's MOPA laser diode for laser communications. Methods for achieving high data rates will be discussed. Output power and beam quality measurements will be made, as well as characterization under high speed modulation (>1GHz).
Proc. SPIE. 2123, Free-Space Laser Communication Technologies VI
KEYWORDS: Mirrors, Digital signal processing, Sensors, Satellites, Telecommunications, Signal processing, Acquisition tracking and pointing, Satellite communications, Laser communications, Laser systems engineering
Satellite jitter adversely affects pointing, acquisition and tracking (PAT) functions of an intersatellite laser communication system. Reliable aircraft- based testing of PAT systems requires that the detrimental effects of aircraft jitter be controlled and a realistic satellite jitter environment be emulated. A novel jitter rejection technique, the self-tuning feedforward compensation scheme, is developed to minimize effects of aircraft vibration on the PAT terminal. The self-tuning results in the implicit characterization of the mechanical jitter propagation path thus facilitating the injection of prerecorded satellite jitter in the control circuitry of steering mirrors.
Space based optical communications offer several advantages over traditional RF systems. They include: smaller beam divergence, smaller antennas, higher data rates, low probability of intercept, reduced EMI, and low probability of jamming. Additionally, the potentials for light weight, small volume and low power terminals make laser communications a consideration for several potential DOD programs. There have been may proposed configurations for both the laser communication terminal and the satellite network but architectures have remained fairly fluid. Despite these changes, there are several enabling technologies that must be fostered to meet program requirements. Efforts at Rome Lab are currently directed to the development of higher powered laser transmitters; rapid and accurate pointing, acquisition, and tracking systems; multiple channel operation; and sensitive low noise receivers. This paper will provide an overview of these efforts.
In the area of free space optical communications a significant amount of attention has been given to the overall problems of the acquisition and tracking of satellites. Accomplishing these functions with minimal investment in hardware size, weight, and power is essential to the successful evolution of space laser communications (LASERCOM). This paper studies and compares two different types of nonmechanical laser beam steering/diverging devices. A nematic liquid crystal phased array has been tested and compared to an acousto-optic Bragg cell. Both electro-optic devices are capable of simultaneous laser beam spoiling and steering which will provide an alternative to the use of electromechanical hardware for acquisition, fine tracking and point ahead in LASERCOM terminals. Characteristics such as optical efficiency, response time, beam steer range and divergence and power consumption have been measured. Device design and performance parameters are described.