Robert J. De Rosa, European Southern Observatory Santiago
Meiji M. Nguyen, University of California, Berkeley
Jeffrey Chilcote, University of Notre Dame
Bruce MacIntosh, Stanford University
Marshall D. Perrin, Space Telescope Science Institute
Quinn Konopacky, Center for Astrophysics & Space Sciences
Jason J. Wang, California Institute of Technology
Gaspard Duchêne, University of California, Berkeley
Eric L. Nielsen, Stanford University
Julien Rameau, Université Grenoble Alpes
S. Mark Ammons, European Southern Observatory Santiago
Vanessa P. Bailey, European Southern Observatory Santiago
Travis Barman, European Southern Observatory Santiago
Joanna Bulger, European Southern Observatory Santiago
Tara Cotten, European Southern Observatory Santiago
Rene Doyon, Institut de Recherche sur les Exoplanètes
Thomas M. Esposito, University of California, Berkeley
Michael P. Fitzgerald, European Southern Observatory Santiago
Katherine B. Follette, European Southern Observatory Santiago
Benjamin L. Gerard, European Southern Observatory Santiago
Stephen J. Goodsell, Stanford University
James R. Graham, University of California, Berkeley
Alexandra Z. Greenbaum, Stanford University
Pascale Hibon, European Southern Observatory Santiago
Li Wei Hung, Stanford University
Patrick Ingraham, Stanford University
Paul Kalas, University of California, Berkeley
James E. Larkin, European Southern Observatory Santiago
Jérôme Maire, Center for Astrophysics & Space Sciences
Franck Marchis, Stanford University
Mark S. Marley, Stanford University
Christian Marois, European Southern Observatory Santiago
Kimberly Ward-Duong, Amherst CollegeFollow
et al, Various Institutions

Document Type


Publication Date


Publication Title

Journal of Astronomical Telescopes, Instruments, and Systems


We present a revision to the astrometric calibration of the Gemini Planet Imager (GPI), an instrument designed to achieve the high contrast at small angular separations necessary to image substellar and planetary-mass companions around nearby, young stars. We identified several issues with the GPI data reduction pipeline (DRP) that significantly affected the determination of the angle of north in reduced GPI images. As well as introducing a small error in position angle measurements for targets observed at small zenith distances, this error led to a significant error in the previous astrometric calibration that has affected all subsequent astrometric measurements. We present a detailed description of these issues and how they were corrected. We reduced GPI observations of calibration binaries taken periodically since the instrument was commissioned in 2014 using an updated version of the DRP. These measurements were compared to observations obtained with the NIRC2 instrument on Keck II, an instrument with an excellent astrometric calibration, allowing us to derive an updated plate scale and north offset angle for GPI. This revised astrometric calibration should be used to calibrate all measurements obtained with GPI for the purposes of precision astrometry.


astrometric calibration, data processing, Gemini Planet Imager, high-contrast imaging










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