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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.
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