Real-Time implementation of an LQG tip-Tilt controller for regular science observation on GeMS

Gaetano Sivo, Rémy Juvénal, Caroline Kulcsár, Vincent Garrel, Pedro Gigoux, Henri François Raynaud, Eduardo Marin, Jean Marc Conan, Cyril Petit, William Rambold, Vanessa Montes, Cristian Moreno, Jeff Donahue, Rodrigo Carrasco, Marcos Van Dam, Benoît Neichel, Lucie Leboulleux, Chad Trujillo

Research output: Chapter in Book/Report/Conference proceedingConference contribution

3 Scopus citations


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.

Original languageEnglish (US)
Title of host publicationAdaptive Optics Systems V
EditorsEnrico Marchetti, Jean-Pierre Veran, Laird M. Close
ISBN (Electronic)9781510601970
StatePublished - 2016
Externally publishedYes
EventAdaptive Optics Systems V - Edinburgh, United Kingdom
Duration: Jun 26 2016Jul 1 2016

Publication series

NameProceedings of SPIE - The International Society for Optical Engineering
ISSN (Print)0277-786X
ISSN (Electronic)1996-756X


ConferenceAdaptive Optics Systems V
Country/TerritoryUnited Kingdom


  • Adaptive Optics
  • GeMS
  • Kalman Filter
  • LQG
  • Multi-Conjugated Adaptive Optics
  • Optimal Control
  • Vibrations Rejection

ASJC Scopus subject areas

  • Electronic, Optical and Magnetic Materials
  • Condensed Matter Physics
  • Computer Science Applications
  • Applied Mathematics
  • Electrical and Electronic Engineering


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