Date of Award

9-2006

Document Type

Thesis

Degree Name

Master of Science in Space Systems

Department

Department of Electrical and Computer Engineering

First Advisor

Juan R. Vaquez, PhD

Abstract

A dual fine tracking control system (FTCS) is developed for a single aperture optical communication receiver to compensate for high frequency disturbances affecting tracking of two incident laser communication beams. The optical communication receiver resides within a payload module aboard a geosynchronous satellite, while each laser communication transmitter is housed within a module aboard a high altitude unmanned aerial vehicle (UAV). In addition to platform specific disturbances, the impact of atmospheric optical disturbances affecting tracking error are investigated. The system dynamics and FTCS are modeled and evaluated in MATLAB and SIMULINK. An optimal controller is developed to mitigate these disturbances and provide tracking errors commensurate with a bit error rate (BER) that does not exceed 10-6.
Based on the respective optimal state estimates of each beam, the dual control technique regulates the fine tracking error for each beam by switching in time between each state estimate and applying linear quadratic regulator (LQR) control to a single fast steering mirror (FSM). Optical turbulence induced random beam wander effects revealed limited impact to tracking error due to spatial separation between transmitters, due to the defined communication architecture geometry. Moreover, simulation results indicated that dual control did not achieve the tracking error limit; however, single control of one beam at the cost of tracking error on the other beam, achieved a sufficient temporal mean tracking error to meet the required BER.

AFIT Designator

AFIT-GSS-ENG-06-02

DTIC Accession Number

ADA456047

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