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13 September 2012 Wavefront sensing and correction with the Gemini Planet Imager
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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.
© (2012) COPYRIGHT Society of Photo-Optical Instrumentation Engineers (SPIE). Downloading of the abstract is permitted for personal use only.
S. Thomas, L. Poyneer, D. Savransky, B. Macintosh, M. Hartung, D. Dillon, D. Gavel, Jennifer Dunn, K. Wallace, D. Palmer, and Robert De Rosa "Wavefront sensing and correction with the Gemini Planet Imager", Proc. SPIE 8447, Adaptive Optics Systems III, 844714 (13 September 2012); doi: 10.1117/12.926680;


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