Optical Beam Jitter Control
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.
Description
The article of record as published may be found at http://dx.doi.org/10.1117/12.529457
Rights
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.Related items
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