Publication:
Vibration Damping for the Segmented Mirror Telescope

Loading...
Thumbnail Image
Authors
Maly, Joseph R.
Yingling, Adam J.
Griffin, Steven F.
Agrawal, Brij N.
Cobb, Richard G.
Chambers, Trevor S.
Subjects
segmented mirror system
actuated hybrid mirror
deformable mirror
wavefront error
image jitter
state space model
passive damping
tuned mass damper
modal testing
laser vibrometry
Advisors
Date of Issue
2012
Date
Publisher
SPIE
Language
Abstract
The Segmented Mirror Telescope (SMT) at the Naval Postgraduate School (NPS) in Monterey is a next-generation deployable telescope, featuring a 3-meter 6-segment primary mirror and advanced wavefront sensing and correction capabilities. In its stowed configuration, the SMT primary mirror segments collapse into a small volume; once on location, these segments open to the full 3-meter diameter. The segments must be very accurately aligned after deployment and the segment surfaces are actively controlled using numerous small, embedded actuators. The SMT employs a passive damping system to complement the actuators and mitigate the effects of low-frequency (<40 Hz) vibration modes of the primary mirror segments. Each of the six segments has three or more modes in this bandwidth, and resonant vibration excited by acoustics or small disturbances on the structure can result in phase mismatches between adjacent segments thereby degrading image quality. The damping system consists of two tuned mass dampers (TMDs) for each of the mirror segments. An adjustable TMD with passive magnetic damping was selected to minimize sensitivity to changes in temperature; both frequency and damping characteristics can be tuned for optimal vibration mitigation. Modal testing was performed with a laser vibrometry system to characterize the SMT segments with and without the TMDs. Objectives of this test were to determine operating deflection shapes of the mirror and to quantify segment edge displacements; relative alignment of N4 or better was desired. The TMDs attenuated the vibration amplitudes by 80% and reduced adjacent segment phase mismatches to acceptable levels.
Type
Article
Description
The article of record as published may be located at http://dx.doi.org/10.1117/12.926567
Series/Report No
Department
Organization
Identifiers
NPS Report Number
Sponsors
Funder
The work described in this paper was funded by the Naval Postgraduate School, Monterey, California. Modal testing was performed with the Air Force Institute of Technology laser vibrometry system.
Format
Citation
Modern Technologies in Space- and Ground-based Telescopes and Instrumentation II, edited by Ramon Navarro, Colin R. Cunningham, Eric Prieto, Proc. of SPIE Vol. 8450, 845004, 2012.
Distribution Statement
Rights
This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.
Collections