29 July 2010 A novel forward-model technique for estimating EUV imaging performance: design and analysis of the SUVI telescope
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Abstract
The Solar Ultraviolet Imager (SUVI) is one of several instruments being fabricated for use on board the upcoming Geostationary Operational Environmental Satellites, GOES-R and -S platforms, as part of NOAA's space weather monitoring fleet. SUVI is a Generalized Cassegrain telescope that employs multilayer coatings optimized to operate in six extreme ultraviolet (EUV) narrow bandpasses centered at 93.9, 131.2, 171.1, 195.1, 284.2 and 303.8 Å. Over the course of its operational lifetime SUVI will image and record full disk, EUV spectroheliograms approximately every few minutes, and telemeter the data to the ground for digital processing. This data will be useful to scientists and engineers wanting to better understand the effects of solar produced EUV radiation with the near-Earth environment. At the focus of the SUVI telescope is a thin, back-illuminated CCD sensor with 21 μm (2.5 arc sec) pixels. At the shortest EUV wavelengths, image degradation from mirror surface scatter effects due to residual optical fabrication errors dominate the effects of both diffraction and geometrical aberrations. Discussed herein, we present a novel forward model that incorporates: (i) application of a new unified surface scatter theory valid for moderately rough surfaces to predict the bidirectional reflectance distribution function (BRDF) produced by each mirror (which uses optical surface metrology to determine the power spectral density, PSD, that characterizes the "smoothness" of an optical surface); (ii) use of the BRDF for each mirror at each EUV wavelength, in tandem with the optical design, to calculate the in-band point spread function (PSF); (iii) use of the PSF to calculate the fractional ensquared energy in the focal plane of SUVI; (iv) comparison of BRDF measurements taken at 93.9 Å with the forward model predictions and (v) final prediction of the in-band, total system responsivity.
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Dennis Martínez-Galarce, Dennis Martínez-Galarce, James Harvey, James Harvey, Marilyn Bruner, Marilyn Bruner, James Lemen, James Lemen, Eric Gullikson, Eric Gullikson, Regina Soufli, Regina Soufli, Evan Prast, Evan Prast, Shayna Khatri, Shayna Khatri, } "A novel forward-model technique for estimating EUV imaging performance: design and analysis of the SUVI telescope", Proc. SPIE 7732, Space Telescopes and Instrumentation 2010: Ultraviolet to Gamma Ray, 773237 (29 July 2010); doi: 10.1117/12.864577; https://doi.org/10.1117/12.864577
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