Space Shuttle Proximity Operation Sensor Study

The performance of the Kuband radar was analyzed in detail, and the performance was updated and summarized. In so doing, two different radar design philosophies were described, and the corresponding differences in losses were enumerated. The resulting design margins were determined for both design philosophies and for both the designated and nondesignated range modes of operation. In some cases, the design margin was about zero, and in other cases it was significantly less than zero. With the point of view described above, the recommended solution is to allow more scan time but at the present scan rate. With no other changes in the present configuration, the radar met design detection specifications for all design philosophies at a range of 11.3 nautical miles

Mean-Field Stochastic Differential Game for Fine Alignment Control of Cooperative Optical Beam Systems

The deployment of autonomous optical link communication platforms that benefit from mobility and optical data rates is essential in public safety communications. However, maintaining an accurate line-of-sight and perfect tracking between mobile platforms or unmanned aerial vehicles (UAVs) in free-space remains challenging for cooperative optical communication due to the underlying mechanical vibration and accidental shocks. Indeed, a misalignment can result in optical channel disconnection, leading to connectivity loss. To address this challenge, we propose a two-way optical link that coordinates mobile UAVs' closed-loop fine beam tracking operation in a swarm architecture to enhance terrestrial public safety communication systems. We study a dynamic of the optical beam tracking games in which each agent's dynamic and cost function are coupled with the other optical beam transceiver agents' states via a mean-field term. We describe a line-of-sight stochastic cooperative beam tracking communication through a mean field game paradigm that can provide reliable network structure and persistent distributed connectivity and communicability. We derive two optimal mean-field beam tracking control frameworks through decentralized and centralized strategies. The solutions of these strategies are derived from forward-backward ordinary differential equations and rely on the linearity Hamilton-Jacobi-Bellman Fokker-Planck (HJB-FP) equations and stochastic maximum principle. Furthermore, we numerically compute the solution pair to the two joint equations using Newton and fixed point iterations methods to verify the existence and uniqueness of the equilibrium that drives the control to a Nash equilibrium for both differential games

Cavity-enhanced superradiant Rayleigh scattering with ultra-cold and Bose-Einstein condensed atoms

We report on the observation of collective atomic recoil lasing and superradiant Rayleigh scattering with ultracold and Bose-Einstein condensed atoms in an optical ring cavity. Both phenomena are based on instabilities evoked by the collective interaction of light with cold atomic gases. This publication clarifies the link between the two effects. The observation of superradiant behavior with thermal clouds as hot as several tens of $\mu\textrm{K}$ proves that the phenomena are driven by the cooperative dynamics of the atoms, which is strongly enhanced by the presence of the ring cavity.Comment: 10 pages, 10 figure

NONLINEAR DETECTION, ESTIMATION, AND CONTROL FOR FREE-SPACE OPTICAL COMMUNICATION

In free-space optical communication, the intensity of a laser beam is modulated by a message, the beam propagates through free-space or atmosphere, and eventually strikes the receiver. At the receiver, an optical sensor converts the optical energy into an electrical signal, which is processed to reconstruct the original message. The promising features of this communication scheme such as high-bandwidth, power efficiency, and security, render it a viable means for high data rate point-to-point communication. In this dissertation, we adopt a stochastic approach to address two major issues associated with free-space optics: digital communication over an atmospheric channel and maintaining optical alignment between the transmitter and the receiver, in spite of their relative motion. Associated with these issues, we consider several detection, estimation, and optimal control problems with point process observations. Although these problems are motivated by applications in free-space optics, they are also of direct relevance to the general field of estimation theory and stochastic control. We study the detection aspect of digital communication over an atmospheric channel. This problem is formulated as an M-ary hypothesis testing problem involving a doubly stochastic marked and filtered Poisson process in white Gaussian noise. The formal solutions we obtain for this problem are hard to express in an explicit form, thus we approximate them by appropriate closed form expressions. These approximations can be implemented using finite-dimensional, nonlinear, causal filters. Regarding the optical alignment issue, we consider two problems: active pointing and cooperative optical beam tracking. In the active pointing scheme that we develop for short range applications, the receiving station estimates the center of its incident optical beam based on the output of a position-sensitive photodetector. The transmitter receives this estimate via an independent communication link and incorporates it to accurately aim at the receiving station. A cooperative optical beam tracking system consists of two stations in such a manner that each station points its optical beam toward the other one. The stations employ the arrival direction of the incident optical beams as a guide to precisely point their own beam toward the other station. We develop a detailed stochastic model for this system and employ it to determine a control law which maximizes the flow of optical energy between the stations. In so doing, we consider the effect of light propagation delay, which requires a point-ahead mechanism to compensate for the displacement of the receiving station during propagation time

Air Force Institute of Technology Research Report 2006

This report summarizes the research activities of the Air Force Institute of Technology’s Graduate School of Engineering and Management. It describes research interests and faculty expertise; lists student theses/dissertations; identifies research sponsors and contributions; and outlines the procedures for contacting the school. Included in the report are: faculty publications, conference presentations, consultations, and funded research projects. Research was conducted in the areas of Aeronautical and Astronautical Engineering, Electrical Engineering and Electro-Optics, Computer Engineering and Computer Science, Systems and Engineering Management, Operational Sciences, Mathematics, Statistics and Engineering Physics