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Proceedings Paper

Wavefront sensing and correction with the Gemini Planet Imager
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Paper Abstract

High-contrast imaging is a growing observational technique aimed at discovering and characterizing extrasolar planets. The Gemini Planet Imager (GPI) is designed to achieve contrast ratios of 10-6 - 10-7 and requires unprecedented wavefront correction and coronagraphic control of diffraction. G PI is a facility instrument now undergoing integration and testing and is scheduled for first light on the 8-m Gemini South telescope towards the end of 2012. In this paper, we focus on the wavefront sensing and correction aspects of the instrument. To measure the wavefront, GPI combines a Shack-Hartmann wavefront sensor and a high-accuracy infrared interferometric wavefront calibration system. The Shack-Hartmann wavefront sensor uses 1700 subapertures to precisely sample the wavefront at 1.5 kHz and features a spatial filter to prevent aliasing. The wavefront calibration system measures the slower temporal frequency errors as well as non-common path aberrations. The wavefront correction is performed using a two-stage adaptive optics system employing a 9x9 piezoelectric deformable mirror and a 43x43 actuators MEMS deformable mirror operating in a woofer-tweeter configuration. Finally, an image sharpening technique is used to further increase the contrast of the final image. In this paper, we describe the three wavefront sensing methods and how we combine their respective information to achieve the best possible contrast.

Paper Details

Date Published: 13 September 2012
PDF: 12 pages
Proc. SPIE 8447, Adaptive Optics Systems III, 844714 (13 September 2012); doi: 10.1117/12.926680
Show Author Affiliations
S. Thomas, Gemini Observatory (United States)
L. Poyneer, Lawrence Livermore National Lab. (United States)
D. Savransky, Lawrence Livermore National Lab. (United States)
B. Macintosh, NRC Herzberg Institute of Astrophysics (Canada)
M. Hartung, Gemini Observatory (United States)
D. Dillon, UCO Lick Observatory (United States)
D. Gavel, UCO Lick Observatory (United States)
Jennifer Dunn, NRC Herzberg Institute of Astrophysics (Canada)
K. Wallace, Jet Propulsion Lab. (United States)
D. Palmer, Lawrence Livermore National Lab. (United States)
Robert De Rosa, Univ. of Exeter (United Kingdom)

Published in SPIE Proceedings Vol. 8447:
Adaptive Optics Systems III
Brent L. Ellerbroek; Enrico Marchetti; Jean-Pierre Véran, Editor(s)

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