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9 April 2019 Principal component analysis of up-the-ramp sampled infrared array data
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Abstract
We describe the results of principal component analysis (PCA) of up-the-ramp sampled infrared (IR) array data from the Hubble Space Telescope wide field camera 3 (WFC3 IR), James Webb Space Telescope NIRSpec, and prototype Wide Field Infrared Survey Telescope’s wide field instrument detectors. These systems use, respectively, Teledyne H1R, H2RG, and H4RG-10 near-IR detector arrays with a variety of IR array controllers. The PCA shows that the Legendre polynomials approximate the principal components of these systems (i.e., they roughly diagonalize the covariance matrix). In contrast to the monomial basis that is widely used for polynomial fitting and linearization today, the Legendre polynomials are an orthonormal basis. They provide a quantifiable, compact, and (nearly) linearly uncorrelated representation of the information content of the data. By fitting a few Legendre polynomials, nearly all of the meaningful information in representative WFC3 astronomical datacubes can be condensed from 15 up-the-ramp samples down to 6 compressible Legendre coefficients per pixel. The higher order coefficients contain time domain information that is lost when one projects up-the-ramp sampled datacubes onto two-dimensional images by fitting a straight line, even if the data are linearized before fitting the line. Going forward, we believe that this time domain information is potentially important for disentangling the various nonlinearities that can affect IR array observations, i.e., inherent pixel nonlinearity, persistence, burn in, brighter-fatter effect, (potentially) nonlinear interpixel capacitance, and perhaps others.
© 2019 Society of Photo-Optical Instrumentation Engineers (SPIE) 2329-4124/2019/$25.00 © 2019 SPIE
Bernard J. Rauscher, Richard G. Arendt, Dale J. Fixsen, Alexander Kutyrev, Gregory Mosby, and Samuel H. Moseley "Principal component analysis of up-the-ramp sampled infrared array data," Journal of Astronomical Telescopes, Instruments, and Systems 5(2), 028001 (9 April 2019). https://doi.org/10.1117/1.JATIS.5.2.028001
Received: 23 April 2018; Accepted: 4 February 2019; Published: 9 April 2019
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