Construction and status of the CHARIS high contrast imaging spectrograph

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.

Temperature-dependent refractive index measurements of CaF2, Suprasil 3001, and S-FTM16 for the Euclid near-infrared spectrometer and photometer

“…To that end, CHARMS has supported a wide variety of international programs including JWST, the Keck Multi-Object Spectrometer for Infra-Red Exploration (MOSFIRE) 5 , the ESO UT1 CRyogenic high-resolution InfraRed Echelle Spectrograph (CRIRES) 6 and VLT K-band Multi-Object Spectrograph (KMOS) 7 and X-shooter near IR spectrograph 8 , the GMT Near Infrared Multi-Object Spectrograph (NIRMOS) 9 , the Euclid Near Infrared Spectrometer and Photometer (NISP) 10,11 , NASA's Transiting Exoplanet Survey Satellite (TESS) 12 and Wide Field Infrared Survey Telescope (WFIRST) 13 , and the CHARIS high contrast imaging spectrograph for the Subaru telescope. 14,15 CHARMS has now been used for measurements at wavelengths as low as 0.35 µm in the near UV and to temperatures as high as 335 K (62 C). Figure 1 is a photograph of CHARMS at GSFC.…”

SEEDS — Strategic explorations of exoplanets and disks with the Subaru Telescope —

“… 60 ) These are equipped with extreme adaptive optics with ∼1–2 k actuators and integrated field spectrometers (IFS). The Subaru Telescope is being upgraded to include its own extreme adaptive optics with ∼2 k actuator (SCExAO) 61 , 62 ) and IFS (CHARIS), 63 ) which will be in its full performance and available in the coming years, respectively. An infrared high-precision radial spectrometer (IRD) equipped with a laser frequency comb is also near commissioning for earth-like planets and super-earths around nearby red dwarfs.…”

DARKNESS: A Microwave Kinetic Inductance Detector Integral Field Spectrograph for High-contrast Astronomy

“…Finally, the remaining light is sent to the science instrument backend for imaging, spectroscopy, and/or polarimetry depending on the particular system's science instrument suite. While the exact capabilities vary from one system to another, each of the systems listed above features an integral field spectrograph (IFS) among their science instruments that returns a spectrum at each spatial element in the final image (Hinkley et al 2008;Larkin et al 2014;Claudi et al 2008;Groff et al 2014). With this configuration the majority of the overwhelming starlight can be suppressed, revealing nearby faint companions or disk systems with simultaneous imaging and spectroscopy (Oppenheimer et al 2013).…”