Gemini planet imager observational calibrations V: Astrometry and distortion

Quinn M. Konopacky, Sandrine J. Thomas, Bruce A. MacIntosh, Daren Dillon, Naru Sadakuni, Jérôme Maire, Michael Fitzgerald, Sasha Hinkley, Paul Kalas, Thomas Esposito, Christian Marois, Patrick J. Ingraham, Franck Marchis, Marshall D. Perrin, James R. Graham, Jason J. Wang, Robert J. De Rosa, Katie Morzinski, Laurent Pueyo, Jeffrey K. ChilcoteJames E. Larkin, Daniel Fabrycky, Stephen J. Goodsell, Ben R. Oppenheimer, Jenny Patience, Leslie Saddlemyer, Anand Sivaramakrishnan

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

40 Scopus citations


We present the results of both laboratory and on sky astrometric characterization of the Gemini Planet Imager (GPI). This characterization includes measurement of the pixel scale∗ of the integral field spectrograph (IFS), the position of the detector with respect to north, and optical distortion. Two of these three quantities (pixel scale and distortion) were measured in the laboratory using two transparent grids of spots, one with a square pattern and the other with a random pattern. The pixel scale in the laboratory was also estimate using small movements of the artificial star unit (ASU) in the GPI adaptive optics system. On sky, the pixel scale and the north angle are determined using a number of known binary or multiple systems and Solar System objects, a subsample of which had concurrent measurements at Keck Observatory. Our current estimate of the GPI pixel scale is 14.14 ± 0.01 millarcseconds/pixel, and the north angle is -1.00 ± 0.03°. Distortion is shown to be small, with an average positional residual of 0.26 pixels over the field of view, and is corrected using a 5th order polynomial. We also present results from Monte Carlo simulations of the GPI Exoplanet Survey (GPIES) assuming GPI achieves ∼1 milliarcsecond relative astrometric precision. We find that with this precision, we will be able to constrain the eccentricities of all detected planets, and possibly determine the underlying eccentricity distribution of widely separated Jovians.

Original languageEnglish (US)
Title of host publicationGround-Based and Airborne Instrumentation for Astronomy V
EditorsSuzanne K. Ramsay, Ian S. McLean, Hideki Takami
ISBN (Electronic)9780819496157
StatePublished - 2014
EventGround-Based and Airborne Instrumentation for Astronomy V - Montreal, Canada
Duration: Jun 22 2014Jun 26 2014

Publication series

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


ConferenceGround-Based and Airborne Instrumentation for Astronomy V


  • GPI
  • Gemini Planet Imager
  • astrometry
  • calibration
  • distortion
  • high contrast imaging
  • integral field spectroscopy
  • planetary dynamics

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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