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Proceedings Paper

MMT adaptive secondary: performance evaluation and field testing
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Paper Abstract

The adaptive secondary for the MMT (called MMT336) is the first mirror of its kind. It was designed to allow the application of wavefront corrections (including tip-tilt) directly at the secondary mirror location. Among the advantages of such a choice for adaptive optics operation are higher throughput, lower emissivity, and simpler optical setup. The mirror also has capabilities that are not found in most correctors including internal position feedback, large stroke (to allow chopping) and provision for absolute position calibration. The 336 actuator adaptive secondary for MMT has been used daily for over one year in our adaptive optics testing facility which has built confidence in the mirror operation and allowed us to interface it to the MMT adaptive optics system. Here we present the most recent data acquired in the lab on the mirror performance. By using interferometer measurements we were able to achieve a residual surface error of approximately 40nm rms. Coupling the mirror with a Shack-Hartmann wavefront sensor we obtained a stable closed loop operation with a -3dB closed loop bandwidth of approximately 30Hz limited by the wavefront sensor frame rate. We also present some preliminary results that show a 5Hz, 90% duty cycle, ±5 arcsec chopping of the mirror. Finally the experience gained and the problems encountered during the first light adaptive optics run at the telescope will be briefly summarized. A more extensive report can be found in another paper also presented at this conference.

Paper Details

Date Published: 7 February 2003
PDF: 12 pages
Proc. SPIE 4839, Adaptive Optical System Technologies II, (7 February 2003); doi: 10.1117/12.459786
Show Author Affiliations
Guido Brusa, Steward Observatory/Univ. of Arizona and Osservatorio Astrofisico di Arcetri (United States)
Armando Riccardi, Osservatorio Astrofisico di Arcetri (Italy)
Piero Salinari, Osservatorio Astrofisico di Arcetri (Italy)
Francois P. Wildi, Steward Observatory/Univ. of Arizona (United States)
Michael Lloyd-Hart, Steward Observatory/Univ. of Arizona (United States)
Hubert M. Martin, Steward Observatory/Univ. of Arizona (United States)
Richard Allen, Steward Observatory/Univ. of Arizona (United States)
Donald Fisher, Steward Observatory/Univ. of Arizona (United States)
Doug L. Miller, Steward Observatory/Univ. of Arizona (United States)
Roberto Biasi, Microgate S.r.l. (Italy)
Daniele Gallieni, ADS International S.r.l. (Italy)
Fabio Zocchi, Media Lario S.r.l. (Italy)

Published in SPIE Proceedings Vol. 4839:
Adaptive Optical System Technologies II
Peter L. Wizinowich; Domenico Bonaccini, Editor(s)

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