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Cornell Caltech Atacama Telescope primary mirror surface sensing and controllability

MacDonald, Daniel and Woody, David and Bradford, C. Matt and Chamberlin, Richard and Dragovan, Mark and Goldsmith, Paul and Radford, Simon and Sebring, Thomas and Zmuidzinas, Jonas (2008) Cornell Caltech Atacama Telescope primary mirror surface sensing and controllability. In: Ground-based and Airborne Telescopes II. Proceedings of SPIE. No.7012. Society of Photo-optical Instrumentation Engineers (SPIE) , Bellingham, WA, Art. No. 701211. ISBN 9780819472229. https://resolver.caltech.edu/CaltechAUTHORS:20181113-084624022

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Abstract

To meet the 10 µm RMS half wavefront error requirement for the 25 m diameter Cornell Caltech Atacama Telescope (CCAT), active control of the approximately 200 primary mirror panels is required. The CCAT baseline design includes carbon fiber aluminum honeycomb sandwich mirror panels. Distortions of the panels due to thermal gradients, gravity and the mounting scheme need to be taken into consideration in the control system design. We have modeled the primary mirror surface as both flat and curved surfaces and have investigated mirror controllability with a variety of sensor types and positions. To study different mirror segmentation schemes and find acceptable sensor configurations, we have created a software package that supports multiple segment shapes and reconfigurable panel sizing and orientation. It includes extensible sensor types and flexible positioning. Inclusion of panel and truss deformations allows modeling the effects of thermal and gravity distortions on mirror controllability. Flat mirrors and curved mirrors with the correct prescription give similar results for controlled modes, but show significant differences in the unsensed flat mirror modes. Both flat and curved mirror models show that sensing schemes that work well with rigid, thermally stable panels will not control a mirror with deformable panels. Sensors external to the mirror surface such as absolute distance measurement systems or Shack-Hartmann type sensors are required to deal with panel deformations. Using a combination of segment based sensors and external sensors we have created a promising prototype control system for the CCAT telescope.


Item Type:Book Section
Related URLs:
URLURL TypeDescription
https://doi.org/10.1117/12.790528DOIArticle
ORCID:
AuthorORCID
Bradford, C. Matt0000-0001-5261-7094
Goldsmith, Paul0000-0002-6622-8396
Additional Information:© 2008 Society of Photo-optical Instrumentation Engineers (SPIE). This research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration.
Funders:
Funding AgencyGrant Number
NASA/JPL/CaltechUNSPECIFIED
Subject Keywords:CCAT, large telescopes, segmented mirrors, mirror alignment, telescope control
Series Name:Proceedings of SPIE
Issue or Number:7012
Record Number:CaltechAUTHORS:20181113-084624022
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20181113-084624022
Official Citation:Daniel MacDonald, David Woody, C. Matt Bradford, Richard Chamberlin, Mark Dragovan, Paul Goldsmith, Simon Radford, Thomas Sebring, Jonas Zmuidzinas, "Cornell Caltech Atacama Telescope primary mirror surface sensing and controllability," Proc. SPIE 7012, Ground-based and Airborne Telescopes II, 701211 (17 July 2008)
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:90854
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:13 Nov 2018 17:48
Last Modified:09 Mar 2020 13:18

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