A new slow focus sensor for GeMS

Eduardo Marin, Vincent Garrel, Gaetano Sivo, Vanessa Montes, Chadwick Trujillo, William Rambold, Pedro Gigoux, Cristian Moreno, Ramon Galvez, Gaston Gausachs, Matthieu Barreau

Research output: Contribution to conferencePaperpeer-review

1 Scopus citations


The Gemini South 8-meter telescope's Multi Conjugate Adaptive Optics System GeMS is about to enter a new era of science with an entire new upgrade for its Natural Guide Star wave front sensor (NGS2). With NGS2 the limiting magnitude of the natural guide stars used for tip/tilt sensing is expected to increase from its current limit of 15.4 to 17+ in R-band. This will provide a much greater sky coverage over the current system. NGS2 is a complete replacement of the current Natural Guide Star wave front sensor (NGS). This presents an interesting challenge as the current NGS includes a Slow Focus Sensor (SFS) used to compensate for the sodium layer mean altitude variations. With the new NGS2 setup, this SFS will be removed and a suitable replacement must be found. Within the Gemini environment there exist two facility wave front sensors, Peripheral Wave Front Sensors one and two (PWFS1 and PWFS2), that could act as an SFS. Only one of these (PWFS1) is located optically in front of the GeMS Adaptive Optics (AO) bench (Canopus). We are currently preparing this wave front sensor as the new SFS for GeMS under the NGS2 setup. The results of several nighttime and daytime tests show that PWFS1 will be an adequate SFS for GeMS in the NGS2 setup providing excellent sky coverage without compromising the GeMS Field of View (FoV).

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


  • AO
  • LGS
  • MCAO

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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