Abstract. 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 Multi-Spectral Solar Telescope Array (MSSTA) is a sounding rocket-borne observatory composed of a set of normalincidence multilayer-coated telescopes that obtained selected bandpass spectroheliograms (44A -1550A) of the Solar atmosphere. These spectroheliograms were recorded on specially fabricated XUV and FUV 70mm Kodak film. Rocket launches of this instrument payload took place in 1991 (MSSTA 1) and 1994 (MSSTA II) at the White Sands Missile Test Range in New Mexico, sponsored by the NASA sounding rocket experiment program. Immediately prior to the 1994 launch, visible light focusing tests of each telescope were performed in-situ using a 195 1 Standard Air Force High Resolution Testtarget, to measure optical resolution performance. We determined that the MSSTA II telescopes performed at diffractionlimited resolutions down to 0.70 arc-second at visible wavelengths. Based on these measurements, we calculated an upperbound to the focusing errors that incorporate the sum of all uncorrelated system resolution errors that affect resolution performance. Coupling these upper-bound estimates with the in-band diffraction limits, surface scattering errors and payload pointing jitter, we demonstrate that eleven of nineteen MSSTA II telescopeshaving negligible figures of focus errors in comparison to the corresponding visible diffraction limitsperformed at sub arc-second resolution at their operational FUV/EUV/XUV wavelengths during flight. We estimate the in-band performance down to 0.14 0.08 second of arc. Downloaded From: http://proceedings.spiedigitallibrary.org/ on 03/03/2016 Terms of Use: http://spiedigitallibrary.org/ss/TermsOfUse.aspx measurement of the in-band point spread function was not performed as it is a difficult and expensive measurement to conduct properly.Prior to the initial flight of multilayer telescopes in wavelength bands centered at I 73A and 256A, the Stanford-MSFC-LLNL consortium carried out a resolution test on a specially prepared Cassegrain telescope at 44.3A (identical to the 173A Cassegrain) using multilayer mirrors designed to reflect the C Ka line. These tests were carried out in the MSFC Xray Calibration Facility (XRCF) by Lindblom et al., 10, 11 who showed that the resolution of the multilayer mirrors was limited by the aberrations of the mirror substrates and also because of a mechanical deformation of the primary mirror introduced by its holding mechanism. Although efficiency tests have been carried out on all multilayer optical systems subsequently flown, the difficulty and expense of fabricating optical testing systems that can image the characteristic soft xray and EUV wavelengths that can be generated with laboratory sources, has precluded in-band resolution testing. Instead, we have carried out resolution tests at optical wavelengths using laser interferometric techniques to verify the optical figure, alignment and spatial frequency response of our flight telescopes. Coupled with these interferometric tests, visible light imaging measurements using a calibrated, standard high r...
A coronal funnel model, developed by D. Rabin, was tested against a calibrated spectroheliogram recorded in the 170-175 Å bandpass. This image was recorded on board a sounding-rocket experiment flown on 1994 November 3, called the Multi-Spectral Solar Telescope Array II (MSSTA II). MSSTA, a joint project of Stanford University, the NASA Marshall Space Flight Center, and the Lawrence Livermore National Laboratory, is an observing platform composed of a set of normal-incidence, multilayer-coated optics designed to obtain narrow-bandpass, high-resolution images (1 00 -3 00 ) at selected far-ultraviolet (FUV), extreme-ultraviolet (EUV), and soft X-ray wavelengths (44-1550 Å ). Using full-disk images centered at 1550 Å (C iv) and 173 Å (Fe ix/x), the funnel model, which is based on coronal back-heating, was tested against the data incorporating observed constraints on global coverage and measured flux. Found was a class of funnel models that could account for the quiescent, globally diffuse and unresolved emission seen in the 171-175 Å bandpass, where the funnels are assumed to be rooted in the C iv supergranular network. These models, when incorporated with the CHIANTI spectral code, suggest that this emission is mostly of upper transition region origin and primarily composed of Fe ix plasma. The funnels are found to have constrictions, À $ 6 20, which is in good agreement with the observations. Further, the fitted models simultaneously satisfy global areal constraints seen in both images; namely, that a global network of funnels must cover $70%-95% of the total solar surface area seen in the 171-175 Å image, and j45% of the disk area seen in the 1550 Å bandpass. These findings support the configuration of the EUV magnetic network as suggested by Reeves et al. and put forth in more detail by Gabriel. Furthermore, the models are in good agreement with differential emission measure estimates made of the transition region by J. C. Raymond & J. G. Doyle for temperatures 250;000 K T 650;000 K, based on full-disk observations made on board Skylab.
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