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LSST M1M3 active mirror support system optimized to accommodate rapid telescope motions
Author(s): Felipe Daruich; Douglas Neill; Michael Warner; Edward Hileman; Myung Cho; Christoph Dribusch; Constanza Araujo; Michael Booth; Christopher Contaxis; Ron Harris; Brian Johnson; Garry Knight; Neill Mills; Gary Muller; Edward Stover; Oliver Wiecha; Bo Xin
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Paper Abstract

The Large Synoptic Survey Telescope is an 8.4m telescope now in construction on Cerro Pachón, in Chile. This telescope is designed to conduct a 10-year survey of the southern sky in which it will map the entire night sky every few nights. In order to achieve this goal, the telescope mount has been designed to achieve high accelerations that will allow the system to change the observing field in just 2 seconds. These rapid slews will subject the M1M3 mirror to high inertial and changing gravitational forces that has to be actively compensated for in order to keep the mirror safe, aligned, and properly figured during operations. The LSST M1M3 active support system is composed of six “hard point” actuators and 156 pneumatic actuators. The hard points define the mirror position in the mirror cell (with little or no applied force) and hold that position while observing in order to maintain the alignment of the telescope optics. The pneumatic actuators provide the force-distributed mirror support plus a known (static) figure correction as well as dynamic optical figure optimizations coming from other components of the Active Optics System. Optimizing this mirror support system required the introduction of innovative control concepts in the control loops (Inner and Outer). The Inner Loop involves an extensive pressure control loop to ensure precise force feedback for each pneumatic actuator while the Outer Loop includes telescope motion sensors to provide the real-time feedback to compensate for the changing external inertial and gravitational forces. These optimizations allow the mirror support system to maximize the hard point force-offloading while keeping the glass safe when slewing and during seismic events.

Paper Details

Date Published: 6 July 2018
PDF: 16 pages
Proc. SPIE 10700, Ground-based and Airborne Telescopes VII, 107003G (6 July 2018); doi: 10.1117/12.2313724
Show Author Affiliations
Felipe Daruich, Large Synoptic Survey Telescope (United States)
Douglas Neill, Large Synoptic Survey Telescope (United States)
Michael Warner, Large Synoptic Survey Telescope (Chile)
Edward Hileman, Large Synoptic Survey Telescope (United States)
Myung Cho, National Optical Astronomy Observatory (United States)
Christoph Dribusch, National Optical Astronomy Observatory (United States)
Constanza Araujo, Large Synoptic Survey Telescope (United States)
Michael Booth, Large Synoptic Survey Telescope (United States)
Christopher Contaxis, Large Synoptic Survey Telescope (United States)
Ron Harris, National Optical Astronomy Observatory (United States)
Brian Johnson, Large Synoptic Survey Telescope (United States)
Garry Knight, Garry Knight LLC (United States)
Neill Mills, Large Synoptic Survey Telescope (United States)
Gary Muller, Large Synoptic Survey Telescope (United States)
Edward Stover, Large Synoptic Survey Telescope (United States)
Oliver Wiecha, Large Synoptic Survey Telescope (United States)
Bo Xin, Large Synoptic Survey Telescope (United States)


Published in SPIE Proceedings Vol. 10700:
Ground-based and Airborne Telescopes VII
Heather K. Marshall; Jason Spyromilio; Roberto Gilmozzi, Editor(s)

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