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Proceedings Paper

Construction and status of the CHARIS high contrast imaging spectrograph
Author(s): Tyler D. Groff; N. Jeremy Kasdin; Mary Anne Limbach; Michael Galvin; Michael A. Carr; Gillian Knapp; Timothy Brandt; Craig Loomis; Norm Jarosik; Kyle Mede; Michael W. McElwain; Markus Janson; Olivier Guyon; Nemanja Jovanovic; Naruhisa Takato; Frantz Martinache; Masahiko Hayashi
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Paper Abstract

Princeton University is building the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS), an integral field spectrograph (IFS) for the Subaru telescope. CHARIS is funded by the National Astronomical Observatory of Japan and is designed to take high contrast spectra of brown dwarfs and hot Jovian planets in the coronagraphic image provided by the Coronagraphic Extreme Adaptive Optics (SCExAO) and the AO188 adaptive optics systems. The project is now in the build and test phase at Princeton University. Once laboratory testing has been completed CHARIS will be integrated with SCExAO and AO188 in the winter of 2016. CHARIS has a high-resolution characterization mode in J, H, and K bands. The average spectral resolution in J, H, and K bands are R82, R68, and R82 respectively, the uniformity of which is a direct result of a new high index material, L-BBH2. CHARIS also has a second low-resolution imaging mode that spans J,H, and K bands with an average spectral resolution of R19, a feature unique to this instrument. The field of view in both imaging modes is 2.07x2.07 arcseconds. SCExAO+CHARIS will detect objects five orders of magnitude dimmer than their parent star down to an 80 milliarcsecond inner working angle. The primary challenge with exoplanet imaging is the presence of quasi-static speckles in the coronagraphic image. SCExAO has a wavefront control system to suppress these speckles and CHARIS will address their impact on spectral crosstalk through hardware design, which drives its optical and mechanical design. CHARIS constrains crosstalk to be below 1% for an adjacent source that is a full order of magnitude brighter than the neighboring spectra. Since CHARIS is on the Nasmyth platform, the optical alignment between the lenslet array and prism is highly stable. This improves the stability of the spectra and their orientation on the detector and results in greater stability in the wavelength solution for the data pipeline. This means less uncertainty in the post-processing and less overhead for on-sky calibration procedures required by the data pipeline. Here we present the science case, design, and construction status of CHARIS. The design and lessons learned from testing CHARIS highlights the choices that must be considered to design an IFS for high signal-to-noise spectra in a coronagraphic image. The design considerations and lessons learned are directly applicable to future exoplanet instrumentation for extremely large telescopes and space observatories capable of detecting rocky planets in the habitable zone.

Paper Details

Date Published: 18 July 2014
PDF: 10 pages
Proc. SPIE 9147, Ground-based and Airborne Instrumentation for Astronomy V, 91471W (18 July 2014); doi: 10.1117/12.2055769
Show Author Affiliations
Tyler D. Groff, Princeton Univ. (United States)
N. Jeremy Kasdin, Princeton Univ. (United States)
Mary Anne Limbach, Princeton Univ. (United States)
Michael Galvin, Princeton Univ. (United States)
Michael A. Carr, Princeton Univ. (United States)
Gillian Knapp, Princeton Univ. (United States)
Timothy Brandt, Princeton Univ. (United States)
Craig Loomis, Princeton Univ. (United States)
Norm Jarosik, Princeton Univ. (United States)
Kyle Mede, National Astronomical Observatory of Japan (Japan)
Michael W. McElwain, NASA Goddard Space Flight Ctr. (United States)
Markus Janson, Princeton Univ. (United States)
Olivier Guyon, Subaru Telescope, National Astronomical Observatory of Japan (United States)
Nemanja Jovanovic, Subaru Telescope, National Astronomical Observatory of Japan (United States)
Naruhisa Takato, Subaru Telescope, National Astronomical Observatory of Japan (United States)
Frantz Martinache, Subaru Telescope, National Astronomical Observatory of Japan (United States)
Masahiko Hayashi, National Astronomical Observatory of Japan (Japan)

Published in SPIE Proceedings Vol. 9147:
Ground-based and Airborne Instrumentation for Astronomy V
Suzanne K. Ramsay; Ian S. McLean; Hideki Takami, Editor(s)

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