Analysis of GeMS tip-tilt on-sky data: LQG implementation for vibration rejections

Lucie Leboulleux, Gaetano Sivo, Rémy Juvénal, Caroline Kulcsár, Vincent Garrel, Henri François Raynaud, Jean Marc Conan, Cyril Petit, William Rambold, Pedro Gigoux, Eduardo Marin, Vanessa Montes, Cristian Moreno, Chad Trujillo

Research output: Contribution to conferencePaperpeer-review

1 Scopus citations


Adaptive Optics (AO) systems aim at detecting and correcting for optical distortions induced by atmospheric turbulences on ground based telescopes astronomical images. They are also extremely sensitive to extraneous sources of perturbations such as vibrations, which degrade their performance. A new well defined vibration at 37Hz has been detected in January 2015 and is still currently affecting the Gemini South telescope secondary mirror. We show how its existence limits the performance of the operational systems at Gemini South: The Gemini Planet Imager (GPI) and the Gemini Multi-Conjugated AO system (GeMS). We further focus on how these vibrations are affecting GeMS performance and propose to implement the Tip-Tilt control strategy first tested on CANARY and routinely used on SPHERE. It combines identification of a sum of auto-regressive models of order 2 with a Linear Quadratic Gaussian (LQG) control. LQG is now routinely used for Tip-Tilt and focus control for GPI and has been successfully tested on all modes on CANARY. We show that the expected gain in performance brought by this LQG Tip-Tilt control strategy on GeMS compared with an Integral Controller is on the order of 15 to 20mas. The analysis was conducted in "replay mode" using GeMS Tip-Tilt on-sky data. This allows realistic performance assessment before implementation inside the Real-Time Computer (RTC) of GeMS and on-sky tests during the first semester of 2016.

Original languageEnglish (US)
StatePublished - 2015
Externally publishedYes
Event4th Adaptive Optics for Extremely Large Telescopes, AO4ELT 2015 - Lake Arrowhead, United States
Duration: Oct 26 2015Oct 30 2015


Conference4th Adaptive Optics for Extremely Large Telescopes, AO4ELT 2015
Country/TerritoryUnited States
CityLake Arrowhead


  • Adaptive optics
  • GeMS
  • Kalman filter
  • LQG
  • Multi conjugated adaptive optics
  • Optimal control
  • Vibrations rejection

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Instrumentation
  • Electronic, Optical and Magnetic Materials
  • Space and Planetary Science
  • Astronomy and Astrophysics
  • Mechanical Engineering


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