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Calibration of the instrumental polarization effects of SCExAO-CHARIS’ spectropolarimetric mode

van Holstein, Rob G. and Bos, Steven P. and Ruigrok, Jasper and Lozi, Julien and Guyon, Olivier and Norris, Barnaby and Snik, Frans and Chilcote, Jeffrey and Currie, Thayne and Groff, Tyler D. and 't Hart, Joost and Jovanovic, Nemanja and Kasdin, Jeremy and Kudo, Tomoyuki and Martinache, Frantz and Mazin, Ben and Sahoo, Ananya and Tamura, Motohide and Vievard, Sébastien and Walter, Alex and Zhang, Jin (2020) Calibration of the instrumental polarization effects of SCExAO-CHARIS’ spectropolarimetric mode. In: Ground-based and Airborne Instrumentation for Astronomy VIII. Proceedings of SPIE. No.11447. Society of Photo-Optical Instrumentation Engineers (SPIE) , Bellingham, WA, Art. No. 114475B. ISBN 9781510636811.

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SCExAO at the Subaru telescope is a visible and near-infrared high-contrast imaging instrument employing extreme adaptive optics and coronagraphy. The instrument feeds the near-infrared light (JHK) to the integral field spectrograph CHARIS. Recently, a Wollaston prism was added to CHARIS’ optical path, giving CHARIS a spectropolarimetric capability that is unique among high-contrast imaging instruments. We present a comprehensive and detailed Mueller matrix model describing the instrumental polarization effects of the complete optical path, thus the telescope and instrument, using measurements with the internal source and observations of standard stars. The 22 wavelength bins of CHARIS provide a unique opportunity to investigate in detail the wavelength dependence of the instrumental polarization effects. We find that the image derotator (K-mirror) produces strongly wavelength-dependent crosstalk, in the worst case converting ~95% of the incident linear polarization to circularly polarized light that cannot be measured. We fit the crosstalk of the half-wave plate (HWP) for all wavelengths with a simple two-parameter model of an achromatic HWP consisting of a layer of quartz and a layer of MgF2. While the magnitude of the telescope-induced polarization varies with wavelength, its angle varies solely with the altitude angle of the telescope. We show initial steps toward correcting on-sky data for the instrumental polarization effects, with which we aim to achieve a polarimetric accuracy <0.1% in the degree of linear polarization. Our calibrations of CHARIS’ spectropolarimetric mode enable unique quantitative polarimetric studies of circumstellar disks and planetary and brown dwarf companions.

Item Type:Book Section
Related URLs:
URLURL TypeDescription
van Holstein, Rob G.0000-0003-1520-8405
Lozi, Julien0000-0002-3047-1845
Guyon, Olivier0000-0002-1097-9908
Norris, Barnaby0000-0002-8352-7515
Snik, Frans0000-0003-1946-7009
Chilcote, Jeffrey0000-0001-6305-7272
Currie, Thayne0000-0002-7405-3119
Groff, Tyler D.0000-0001-5978-3247
Jovanovic, Nemanja0000-0001-5213-6207
Kasdin, Jeremy0000-0002-6963-7486
Kudo, Tomoyuki0000-0002-9294-1793
Martinache, Frantz0000-0003-1180-4138
Sahoo, Ananya0000-0003-2806-1254
Tamura, Motohide0000-0002-6510-0681
Vievard, Sébastien0000-0003-4018-2569
Additional Information:© 2020 Society of Photo-Optical Instrumentation Engineers (SPIE). Based on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. R.G. van Holstein thanks ESO for the studentship at ESO Santiago during which part of this project was performed. The research of S.P. Bos and F. Snik leading to these results has received funding from the European Research Council under ERC Starting Grant agreement 678194 (FALCONER). The development of SCExAO was supported by the Japan Society for the Promotion of Science (Grant-in-Aid for Research #23340051, #26220704, #23103002, #19H00703 & #19H00695), the Astrobiology Center of the National Institutes of Natural Sciences, Japan, the Mt Cuba Foundation and the director's contingency fund at Subaru Telescope. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are very fortunate to have the opportunity to conduct observations from this mountain.
Funding AgencyGrant Number
European Southern Observatory (ESO)UNSPECIFIED
European Research Council (ERC)678194
Japan Society for the Promotion of Science (JSPS)23340051
Japan Society for the Promotion of Science (JSPS)26220704
Japan Society for the Promotion of Science (JSPS)23103002
Japan Society for the Promotion of Science (JSPS)19H00703
Japan Society for the Promotion of Science (JSPS)19H00695
National Institutes of Natural Sciences of JapanUNSPECIFIED
Mt. Cuba Astronomical FoundationUNSPECIFIED
Subaru TelescopeUNSPECIFIED
Subject Keywords:SCExAO-CHARIS, spectropolarimetry, high-contrast imaging, near-infrared, instrumental polarization, crosstalk, Mueller matrix model, polarimetric accuracy
Series Name:Proceedings of SPIE
Issue or Number:11447
Record Number:CaltechAUTHORS:20201222-120433541
Persistent URL:
Official Citation:Rob G. van Holstein, Steven P. Bos, Jasper Ruigrok, Julien Lozi, Olivier Guyon, Barnaby Norris, Frans Snik, Jeffrey Chilcote, Thayne Currie, Tyler D Groff, Joost 't Hart, Nemanja Jovanovic, Jeremy Kasdin, Tomoyuki Kudo, Frantz Martinache, Ben Mazin, Ananya Sahoo, Motohide Tamura, Sébastien Vievard, Alex Walter, and Jin Zhang "Calibration of the instrumental polarization effects of SCExAO-CHARIS’ spectropolarimetric mode", Proc. SPIE 11447, Ground-based and Airborne Instrumentation for Astronomy VIII, 114475B (13 December 2020);
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107255
Deposited By: Tony Diaz
Deposited On:22 Dec 2020 20:30
Last Modified:16 Nov 2021 19:01

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