Optical Beam Jitter Control
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Authors
Watkins, R.J.
Chen, J.
Agrawal, B.N.
Shin, Y.S.
Subjects
Advisors
Date of Issue
2004
Date
January 2004
Publisher
Language
Abstract
For several future imaging and communications spacecraft, a challenging area of technology development is the fine
acquisition, tracking, and pointing (ATP) control of the spacecraft and its payload. For example, some spacecraft with
large aperture(s) in the range of 10~30 m diameter requires a few arc-seconds accuracy, 10~15 nano-radians jitter, and a
fast slewing rate to acquire the target. Furthermore these stringent requirements are at risk of great structure and control
interactions. This paper we will focus on the control of optical beam jitter. A Laser Jitter Control (LJC) testbed has
been constructed to test jitter algorithms. The testbed consists of two fast steering mirrors (FSM), three position sensing
modules (PSM), one diode laser, and several beam splitters and mirrors, all on an isolated Newport optical bench. Jitter
is injected with one FSM and the other FSM is used to control it. The jitter spectrum, representing the on-orbit spacecraft and beam jitter environment, contains not only narrow band noise due to rotating devices such as gyroscopes and reaction wheels but also broadband noise. The performance of a Wiener Filter - adaptive algorithm with ideal reference signal is established as the baseline for comparison of adaptive control methods in suppressing both broadband and narrowband disturbances. Specifically, the Least Mean Squares (LMS) approach and the Gradient Adaptive Lattice (GAL) approach are investigated during these experiments.
For several future imaging and communications spacecraft, a challenging area of technology development is the fine
acquisition, tracking, and pointing (ATP) control of the spacecraft and its payload. For example, some spacecraft with
large aperture(s) in the range of 10~30 m diameter requires a few arc-seconds accuracy, 10~15 nano-radians jitter, and a
fast slewing rate to acquire the target. Furthermore these stringent requirements are at risk of great structure and control
interactions. This paper we will focus on the control of optical beam jitter. A Laser Jitter Control (LJC) testbed has
been constructed to test jitter algorithms. The testbed consists of two fast steering mirrors (FSM), three position sensing
modules (PSM), one diode laser, and several beam splitters and mirrors, all on an isolated Newport optical bench. Jitter
is injected with one FSM and the other FSM is used to control it. The jitter spectrum, representing the on-orbit spacecraft and beam jitter environment, contains not only narrow band noise due to rotating devices such as gyroscopes and reaction wheels but also broadband noise. The performance of a Wiener Filter - adaptive algorithm with ideal reference signal is established as the baseline for comparison of adaptive control methods in suppressing both broadband and narrowband disturbances. Specifically, the Least Mean Squares (LMS) approach and the Gradient Adaptive Lattice (GAL) approach are investigated during these experiments.
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Description
The article of record as published may be found at http://dx.doi.org/10.1117/12.529457
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Department
Department of Mechanical and Aerospace Engineering
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Citation
Proceedings of the SPIE Conference on Lasers and Applications in Science and Technology, SPIE paper 5338-20, January 2004.
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This publication is a work of the U.S. Government as defined
in Title 17, United States Code, Section 101. As such, it is in the
public domain, and under the provisions of Title 17, United States
Code, Section 105, is not copyrighted in the U.S.