Advances in edge sensors for the Thirty Meter Telescope primary mirror

Chris Shelton; Terry Mast; Gary Chanan; Jerry Nelson; Lewis C. Roberts Jr.; Mitchell Troy; Mark J. Sirota; Byoung-Joon Seo; Daniel R. MacDonald

doi:10.1117/12.790415

10 July 2008 Advances in edge sensors for the Thirty Meter Telescope primary mirror

Chris Shelton, Terry Mast, Gary Chanan, Jerry Nelson, Lewis C. Roberts Jr., Mitchell Troy, Mark J. Sirota, Byoung-Joon Seo, Daniel R. MacDonald

Author Affiliations +

Proceedings Volume 7012, Ground-based and Airborne Telescopes II; 701210 (2008) https://doi.org/10.1117/12.790415
Event: SPIE Astronomical Telescopes + Instrumentation, 2008, Marseille, France

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.

Citation Download Citation

Chris Shelton, Terry Mast, Gary Chanan, Jerry Nelson, Lewis C. Roberts Jr., Mitchell Troy, Mark J. Sirota, Byoung-Joon Seo, and Daniel R. MacDonald "Advances in edge sensors for the Thirty Meter Telescope primary mirror", Proc. SPIE 7012, Ground-based and Airborne Telescopes II, 701210 (10 July 2008); https://doi.org/10.1117/12.790415

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