TY - JOUR
T1 - Data reduction pipeline for the CHARIS integral-field spectrograph I
T2 - Detector readout calibration and data cube extraction
AU - Brandt, Timothy D.
AU - Rizzo, Maxime
AU - Groff, Tyler
AU - Chilcote, Jeffrey
AU - Greco, Johnny P.
AU - Kasdin, N. Jeremy
AU - Limbach, Mary Anne
AU - Galvin, Michael
AU - Loomis, Craig
AU - Knapp, Gillian
AU - McElwain, Michael W.
AU - Jovanovic, Nemanja
AU - Currie, Thayne
AU - Mede, Kyle
AU - Tamura, Motohide
AU - Takato, Naruhisa
AU - Hayashi, Masahiko
N1 - Funding Information:
This work was performed in part under contract with the Jet Propulsion Laboratory funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. This work was performed in part under a Grant-in-Aid for Scientific Research on Innovative Areas from MEXT of the Japanese government (No. 23103002). This research was based on data collected at the Subaru Telescope, which is operated by the National Astronomical Observatories of Japan. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Mauna Kea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain.
Publisher Copyright:
© 2017 The Authors.
PY - 2017/10/1
Y1 - 2017/10/1
N2 - We present the data reduction pipeline for CHARIS, a high-contrast integral-field spectrograph for the Subaru Telescope. The pipeline constructs a ramp from the raw reads using the measured nonlinear pixel response and reconstructs the data cube using one of three extraction algorithms: Aperture photometry, optimal extraction, or χ2 fitting. We measure and apply both a detector flatfield and a lenslet flatfield and reconstruct the wavelength-A nd position-dependent lenslet point-spread function (PSF) from images taken with a tunable laser. We use these measured PSFs to implement a χ2-based extraction of the data cube, with typical residuals of ∼5% due to imperfect models of the undersampled lenslet PSFs. The full two-dimensional residual of the χ2 extraction allows us to model and remove correlated read noise, dramatically improving CHARIS's performance. The χ2 extraction produces a data cube that has been deconvolved with the line-spread function and never performs any interpolations of either the data or the individual lenslet spectra. The extracted data cube also includes uncertainties for each spatial and spectral measurement. CHARIS's software is parallelized, written in Python and Cython, and freely available on github with a separate documentation page. Astrometric and spectrophotometric calibrations of the data cubes and PSF subtraction will be treated in a forthcoming paper.
AB - We present the data reduction pipeline for CHARIS, a high-contrast integral-field spectrograph for the Subaru Telescope. The pipeline constructs a ramp from the raw reads using the measured nonlinear pixel response and reconstructs the data cube using one of three extraction algorithms: Aperture photometry, optimal extraction, or χ2 fitting. We measure and apply both a detector flatfield and a lenslet flatfield and reconstruct the wavelength-A nd position-dependent lenslet point-spread function (PSF) from images taken with a tunable laser. We use these measured PSFs to implement a χ2-based extraction of the data cube, with typical residuals of ∼5% due to imperfect models of the undersampled lenslet PSFs. The full two-dimensional residual of the χ2 extraction allows us to model and remove correlated read noise, dramatically improving CHARIS's performance. The χ2 extraction produces a data cube that has been deconvolved with the line-spread function and never performs any interpolations of either the data or the individual lenslet spectra. The extracted data cube also includes uncertainties for each spatial and spectral measurement. CHARIS's software is parallelized, written in Python and Cython, and freely available on github with a separate documentation page. Astrometric and spectrophotometric calibrations of the data cubes and PSF subtraction will be treated in a forthcoming paper.
KW - Data processing
KW - deconvolution
KW - infrared spectroscopy
KW - multispectral imaging
KW - point-spread functions
KW - tunable lasers
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U2 - 10.1117/1.JATIS.3.4.048002
DO - 10.1117/1.JATIS.3.4.048002
M3 - Article
AN - SCOPUS:85038612792
SN - 2329-4124
VL - 3
JO - Journal of Astronomical Telescopes, Instruments, and Systems
JF - Journal of Astronomical Telescopes, Instruments, and Systems
IS - 4
M1 - 048002
ER -