CHARIS Construction Status, Design, and Future Science
Abstract
Princeton University is funded by the National Astronomical Observatory of Japan to build an integral field spectrograph (IFS) dubbed the Coronagraphic High Angular Resolution Imaging Spectrograph (CHARIS). CHARIS is part of the ongoing exoplanet science effort at the Subaru Telescope, and will serve as the science imager for the Subaru Coronagraphic Extreme Adaptive Optics (SCExAO) and AO188 systems. The principal science goals are disk imaging and high contrast spectra of brown dwarfs and hot Jovian planets across J, H, and K bands. SCExAO is a coronagraphic and wavefront control system that will be capable of extreme adaptive optics and quasi-static speckle suppression. Speckle suppression is meant to reduce the residual speckle to a level that makes it possible to detect planets at very low inner working angles (~80 mas). Even so, CHARIS must mitigate spectral contamination from the residual speckle halo due to crosstalk between the closely packed spectra of the image. CHARIS mitigates crosstalk via an array of field stops behind the lenslet array and carefully toleranced relay optics. This reduces uncertainty in the measured spectrum of the exoplanets by increasing robustness of the spectrograph to nearby bright speckles. Mitigating crosstalk in hardware both improves science and reduces computational overhead. Combined with a detailed wavefront budget this improves the utility of CHARIS in the speckle control loop. Another defining feature of CHARIS is its disperser design. In addition to imaging in individual J, H, and K bands, CHARIS has a fourth mode that images across all three simultaneously. This required an improvement in the linearity of dispersion from 1.15 to 2.38 microns. To do so the CHARIS project has chosen a new high-index dispersing material and characterized its properties at cryogenic temperatures. We present the build status of the spectrograph, including status and viability of operating an H2RG detector directly using a SAM card via gigabit Ethernet over Linux. In addition to the stated and as-built specifications of the instrument hardware, we discuss the future of science impacts of CHARIS at the Subaru telescope.
- Publication:
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American Astronomical Society Meeting Abstracts #225
- Pub Date:
- January 2015
- Bibcode:
- 2015AAS...22533712G