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Proceedings Paper

Advances in edge sensors for the Thirty Meter Telescope primary mirror
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Paper Abstract

The out-of-plane degrees of freedom (piston, tip, and tilt) of each of the 492 segments in the Thirty Meter Telescope primary mirror will be actively controlled using three actuators per segment and two edge sensors along each intersegment gap. We address two important topics for this system: edge sensor design, and the correction of fabrication and installation errors. The primary mirror segments are passively constrained in the three lateral degrees of freedom. We evaluate the segment lateral motions due to the changing gravity vector and temperature, using site temperature and wind data, thermal modeling, and finite-element analysis. Sensor fabrication and installation errors combined with these lateral motions will induce errors in the sensor readings. We evaluate these errors for a capacitive sensor design as a function of dihedral angle sensitivity. We also describe operational scenarios for using the Alignment and Phasing System to correct the sensor readings for errors associated with fabrication and installation.

Paper Details

Date Published: 10 July 2008
PDF: 13 pages
Proc. SPIE 7012, Ground-based and Airborne Telescopes II, 701210 (10 July 2008); doi: 10.1117/12.790415
Show Author Affiliations
Chris Shelton, Jet Propulsion Lab. (United States)
Terry Mast, Univ. of California, Santa Cruz (United States)
Gary Chanan, Univ. of California, Irvine (United States)
Jerry Nelson, Univ. of California, Santa Cruz (United States)
Lewis C. Roberts Jr., Jet Propulsion Lab. (United States)
Mitchell Troy, Jet Propulsion Lab. (United States)
Mark J. Sirota, Thirty Meter Telescope Corp. (United States)
Byoung-Joon Seo, Jet Propulsion Lab. (United States)
Daniel R. MacDonald, Jet Propulsion Lab. (United States)

Published in SPIE Proceedings Vol. 7012:
Ground-based and Airborne Telescopes II
Larry M. Stepp; Roberto Gilmozzi, Editor(s)

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