24 September 2012 Polarimetric performance of the Gemini Planet Imager
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Abstract
We report on preliminary results from laboratory calibration of the Gemini Planet Imager (GPI) polarimetry mode. Utilizing a linear polarizer and a quarterwave plate in a telescope simulator testbed, we inject a set of 15 Stokes states into GPI that sample the Poincaré sphere. Calibration of the known and measured Stokes parameters allows us to determine the Mueller matrix of the instrument, from which we find that crosstalk from Stokes I to (Q,U) is < 1.5%. This is well within the acceptance test plan requirement that instrumental linear polarization be. However, instrumental circular polarization is 15%. Further testing is needed to identify the source of the significant circular polarization in the system to mitigate its effect on data quality. We find the instrument is sensitive enough to identify stress birefringence of the last lens in the telescope simulator testbed, and we measure it to have a retardance of 0.030 waves.
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Sloane J. Wiktorowicz, Max Millar-Blanchaer, Marshall D. Perrin, James R. Graham, Sandrine J. Thomas, Daren Dillon, Michael P. Fitzgerald, Jérôme Maire, Bruce A. Macintosh, Stephen J. Goodsell, "Polarimetric performance of the Gemini Planet Imager", Proc. SPIE 8446, Ground-based and Airborne Instrumentation for Astronomy IV, 844691 (24 September 2012); doi: 10.1117/12.925239; https://doi.org/10.1117/12.925239
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