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Proceedings Paper

Advanced control of low order modes in laser guide star multi-conjugate adaptive optics systems
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Paper Abstract

Laser-guide-star-based multi-conjugate adaptive optics (MCAO) systems require natural guide-stars to measure tilt and tilt-anisoplanatism modes. This paper focuses on the parameter optimisation of sub-optimal integrator-based controllers using a single and a double integrator (baseline option) to drive the low-order loop of NFIRAOS, the 1st light MCAO system for the Thirty-Meter Telescope. The minimum-variance (MV) controller is outlined, against which integrators are compared. Simulations using ~500 asterisms considered in sky-coverage simulations for the TMT show that the double integrator gives competitive results thoughout the range of asterisms and magnitudes considered. It is shown that using an optimal modal gain integrator can further improve the performance with respect to using an averaged gain for all of part of the modes. However, it is outperformed by the MV controller, in particular for asterisms with relatively dim stars (lower bound is magnitude 22 in H-band) requiring low temporal frame-rates (as low as 16Hz) to integrate more flux. Over all the cases tested, an average of ~100 nm rms (23 nm rms median) improvement can be achieved with the MV. The MV further increases by 15% the probability of working below the 50th-percentile residual of the double integrator.

Paper Details

Date Published: 13 September 2012
PDF: 12 pages
Proc. SPIE 8447, Adaptive Optics Systems III, 84471S (13 September 2012); doi: 10.1117/12.926872
Show Author Affiliations
Carlos Correia, NRC Herzberg Institute of Astrophysics (Canada)
Jean-Pierre Véran, NRC Herzberg Institute of Astrophysics (Canada)
Glen Herriot, NRC Herzberg Institute of Astrophysics (Canada)
Brent Ellerbroek, Thirty Meter Telescope Observatory Corp. (United States)
Lianqi Wang, Thirty Meter Telescope Observatory Corp. (United States)
Luc Gilles, Thirty Meter Telescope Observatory Corp. (United States)

Published in SPIE Proceedings Vol. 8447:
Adaptive Optics Systems III
Brent L. Ellerbroek; Enrico Marchetti; Jean-Pierre Véran, Editor(s)

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