4 October 2016 Real-time implementation of an LQG tip-tilt controller for regular science observation on GeMS
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Abstract
AO systems aim at detecting and correcting for optical distortions induced by atmospheric turbulences. They are also extremely sensitive to extraneous sources of perturbation such as vibrations, which degrade the performance. The Gemini South telescope has currently two main AO systems: the Gemini Multi Conjugated AO System GeMS and the Gemini Planet Imager GPI. GeMS is operational and regularly used for science observation delivering close to diffraction limit resolution over a large field of view (85×85 arcsec2). Performance limitation due to the use of an integrator for tip-tilt control is here explored. In particular, this type of controller does not allow for the mitigation of vibrations with an arbitrary natural frequency. We have thus implemented a tip-tilt Linear Quadratic Gaussian (LQG) controller with different underlying perturbation models: (i) a sum of autoregressive models of order 2 identified from an estimated power spectrum density (s-AR2) of the perturbation,1 already tested on CANARY2 and routinely used on SPHERE;3 (ii) cascaded ARMA models of order 2 identified using prediction error minimization (c-PEM) as proposed in.4, 5 Both s-AR2 and c-PEM were parameterized to produce tip or tilt state-space models up to order 20 and 30 respectively. We discuss the parallelized implementation in the real time computer and the expected performance. On-sky tests are scheduled during the November 2016 run or the January 2017 run.
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Gaetano Sivo, Gaetano Sivo, Rémy Juvénal, Rémy Juvénal, Caroline Kulcsár, Caroline Kulcsár, Vincent Garrel, Vincent Garrel, Pedro Gigoux, Pedro Gigoux, Henri-François Raynaud, Henri-François Raynaud, Eduardo Marin, Eduardo Marin, Jean-Marc Conan, Jean-Marc Conan, Cyril Petit, Cyril Petit, William Rambold, William Rambold, Vanessa Montes, Vanessa Montes, Cristian Moreno, Cristian Moreno, Jeff Donahue, Jeff Donahue, Rodrigo Carrasco, Rodrigo Carrasco, Marcos van Dam, Marcos van Dam, Benoît Neichel, Benoît Neichel, Lucie Leboulleux, Lucie Leboulleux, Chad Trujillo, Chad Trujillo, } "Real-time implementation of an LQG tip-tilt controller for regular science observation on GeMS", Proc. SPIE 9909, Adaptive Optics Systems V, 99094Y (4 October 2016); doi: 10.1117/12.2233191; https://doi.org/10.1117/12.2233191
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