The Solar Ultraviolet Imager (SUVI) is one of the several instruments that will fly on board the next generation of Geostationary Operational Environmental Satellites R-U platforms, as part of the National Oceanic and Atmospheric Administration’s space weather monitoring fleet. SUVI is a generalized Cassegrain telescope that employs multilayer-coated optics that operate in six extreme ultraviolet (EUV) narrow bandpasses centered at 93.9, 131.2, 171.1, 195.1, 284.2 and 303.8 Å. The innovation of the design is that SUVI is the first EUV solar telescope that has six different wavelength channels accommodated on each mirror. And despite having six segmented multilayer-coatings, shadowing (due to the mask) is minimized allowing SUVI to exceed its effective area specifications. Once operational, SUVI will record full-disk, spectroheliograms every few minutes, where this data will be used to better understand the effects of solar produced EUV radiation on Earth and the near-Earth environment. The material presented discusses general aspects of the SUVI optical design, mirror fabrication, super polishing, and metrology carried out to verify optical surface quality and in-band, EUV reflectivity performance of the multilayer coatings. The power spectral density and EUV measurements are shown to exceed performance requirements and are critical for the overall calibration and monitoring of SUVI’s throughput and imaging performance, once operational.
The Solar Ultraviolet Imager (SUVI) is one of several instruments that will fly on board the next generation of
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-coated optics that operate in six
extreme ultraviolet (EUV) narrow bandpasses centered at 93.9, 131.2, 171.1, 195.1, 284.2 and 303.8 Å. Once
operational, over the mission lifetime expected to last up to 10 years, SUVI will record full disk, EUV spectroheliograms
every few minutes, where this data will be used to better understand the effects of solar produced EUV radiation on
Earth and the near-Earth environment. The material presented herein will touch upon general aspects of the SUVI optical
design, as well as the fabrication, super polishing and metrology of the fabricated mirrors, including measured EUV
spectral performance.
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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