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.
This manuscript presents a review of recent advances in EUV/x-ray substrate specification, fabrication and metrology for
photolithography, synchrotron sources, free-electron laser sources, solar physics and astronomy. Highlights from ultra-low-
expansion glass substrates, silicon and silicon carbide substrates are presented. Selected emerging substrate
materials and fabrication technologies are also discussed.
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.
LMSAL and NIST are developing position-sensitive x-ray strip detectors based on Transition Edge Sensor (TES)
microcalorimeters optimized for solar physics. By combining high spectral (E/ΔE ~1600) and temporal (single photon
Δt ~10μs) resolutions with imaging capabilities, these devices will be able to study high-temperature (>10 MK) x-ray
lines as never before. Diagnostics from these lines should provide significant new insight into the physics of both
microflares and the early stages of flares. Previously, the large size of traditional TESs, along with the heat loads
associated with wiring large arrays, presented obstacles to using these cryogenic detectors for solar missions.
Implementing strip detector technology at small scales, however, addresses both issues: here, a line of substantially
smaller effective pixels requires only two TESs, decreasing both the total array size and the wiring requirements for the
same spatial resolution. Early results show energy resolutions of Δ ΕFWHM ~30eV and spatial resolutions of ~10-15 μm,
suggesting the strip-detector concept is viable.
The Micro-X High Resolution Microcalorimeter X-ray Imaging Rocket is sounding rocket experiment that will combine a transition-edge-sensor X-ray-microcalorimeter array with a conical imaging mirror to obtain high-spectral-resolution images of extended and point X-ray sources. Our first target is the Puppis A supernova remnant, which will be observed in January 2011. The Micro-X observation of the bright eastern knot of Puppis A will obtain a line-dominated spectrum with up to 90,000 counts collected in 300 seconds at 2 eV resolution across the 0.3-2.5 keV band. Micro-X will utilize plasma diagnostics to determine the thermodynamic and ionization state of the plasma, to search for line shifts and broadening associated with dynamical processes, and seek evidence of ejecta enhancement. We describe the progress made in developing this payload, including the detector, cryogenics, and electronics assemblies. A detailed modeling effort has been undertaken to design a rocket-bourne adiabatic demagnetization refrigerator with sufficient magnetic shielding to allow stable operation of transition edge sensors, and the associated rocket electronics have been prototyped and tested.
The High-resolution Lightweight Telescope for the EUV (HiLiTE) is a Cassegrain telescope that will be made entirely of
Silicon Carbide (SiC), optical substrates and metering structure alike. Using multilayer coatings, this instrument will be
tuned to operate at the 465 Å Ne VII emission line, formed in solar transition region plasma at ~500,000 K. HiLiTE will
have an aperture of 30 cm, angular resolution of ~0.2 arc seconds and operate at a cadence of ~5 seconds or less, having
a mass that is about 1/4 that of one of the 20 cm aperture telescopes on the Atmospheric Imaging Assembly (AIA)
instrument aboard NASA's Solar Dynamics Observatory (SDO). This new instrument technology thus serves as a path
finder to a post-AIA, Explorer-class missions.
Micro-X is a proposed sounding rocket experiment that will combine a transition-edge-sensor X-ray-microcalorimeter array with a conical imaging mirror to obtain high-spectral-resolution images of extended and point X-ray sources. We describe the payload and the science targeted by this mission including the discussion of three possible Micro- X targets: the Puppis A supernova remnant, the Virgo Cluster, and Circinus X-1. For example, a Micro-X observation of the bright eastern knot of Puppis A will obtain a line-dominated spectrum with 90,000 counts collected in 300 seconds at 2 eV resolution across the 0.3-2.5 keV band. Micro-X will utilize plama diagnostics to determine the thermodynamic and ionization state of the plasma, to search for line shifts and broadening associated with dynamical processes, and seek evidence of ejecta enhancement. For clusters of galaxies, Micro-X can uniquely study turbulence and the temperature distribution function. For binaries, Micro-X's high resolution spectra will separate the different processes contributing to the Fe K lines at 6 keV and give a clear view of the geometry of the gas flows and circumstellar gas.
Superconducting Transition-Edge Sensors (TESs) are generating a great deal of interest in the areas of x-ray astrophysics and space science, particularly to develop them as large-array, imaging x-ray spectrometers. We are developing a novel concept that is based on position-sensitive macro-pixels placing TESs on the backside of a silicon or germanium absorber. Each x-ray absorbed will be position (X/δX and Y/δY ~ 100) and energy (E/δE ~ 1000) resolved via four distributed TES readouts. In the future, combining such macropixels with advances in multiplexing could lead to 30 by 30 arrays of close-packed macro-pixels equivalent to imaging instruments of 10 megapixels or more. We report on our progress to date and discuss its application to a plausible solar satellite mission and plans for future development.
In this paper we present preliminary work on a spatial, arrival time and energy resolving x-ray detector for the study of magnetic reconnection in the solar corona. Our detectors are cryogenic phonon-mediated superconducting Transition-Edge Sensors (TESs). X-rays are incident on a silicon substrate; the generated phonons propagate to the opposite side of the substrate and are absorbed in the tungsten TES electron system. Through a novel spatial distribution of four TESs we aim to achieve simultaneous measurement resolutions of ~10 μm, sub μs, and ~4 eV and with count rates of ~1 kHz. This four TES system is described and preliminary data obtained with a prototype two-channel detector is presented.
We are developing a new sounding rocket payload, the Advanced Technology Solar Spectroscopic Imager (ATSSI), that will use an 8 X 8 array of transition edge sensors (TES) to obtain true spectroheliograms in a spectral bandpass spanning approximately 50 eV to approximately 3 keV. The TES array will be flown at the focus of a Wolter I telescope, where it will image as 3 arc-min by 3 arc-min field of view with a pixel resolution of approximately 6 arc-sec. In this way, it will obtain approximately 1000 individual spectra with an expected average energy resolution of approximately 3 eV FWHM. In addition to the TES array, the ATSSI will employ six multilayer telescopes with bandpasses centered on atomic lines at 17.1 angstrom (Fe XVII), 195.1 angstrom (Fe XII), 171.1 angstrom (Fe IX), 57.9 angstrom (Mg X), 98.3 angstrom (Ne VIII), and 150.1 angstrom (O VI). Two additional telescopes with bandpasses centered at 1550 angstrom (C IV) and 1216 angstrom (H I) will also be used. The eight narrowband telescopes will provide high spatial resolution (<EQ 1 arc- sec), full-disk solar images and will be complemented by two grating slit spectroheliographs. One grating will obtain high resolution spectroheliograms between 2750 angstrom and 2850 angstrom (for Mg II h- and k-line studies), and the other will be multilayer-based and will probe the Fe IX/X - O V/VI complex around 171 Angstrom (73 eV). With this set of instruments, we expect to explore more fully the nature of the energy flow between small-scale coronal, chromospheric and transition region structures, as well as to address the issue of what mechanisms are responsible for heating the quiescent solar atmosphere.
We describe a new payload, the Chromospheric/Coronal Spectroheliograph (CCS), that is optimized for the study of the chromospheric/coronal interface and the search for the sources of energy that sustain the quiescent solar atmosphere. We will utilize the existing optical bench, electronics, and some imaging system from the inventory of multilayer telescopes built up in our previous successful rocket flights of the Multi-Spectral Telescope Array. We will develop several new optical systems to explore more fully the thermal structure of the transition region and introduce a multilayer grating spectroheliograph to permit a more precise determination of the temperature of the structures that control the flow of energy between the chromosphere and the corona.
The Multi-Spectral Solar Telescope Array (MSSTA) is a sounding rocket-borne observatory composed of a set of normal-incidence multilayer-coated telescopes that obtained selected bandpass spectroheliograms 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 and 1994 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 test of each telescope were performed in-situ using a 1951 Standard Air Force High Resolution Test-target, to measure optical resolution performance. We determined that the MSSTA II telescopes performed at diffraction-limited resolutions down to 0.70 arc-second at visible wavelengths. Based on these measurements, we calculated an upper-bound 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 telescopes - having negligible figures of focus errors in comparison to the corresponding visible diffraction limits - performed at sub arc-second resolution at their operation FUV/EUV/XUV wavelengths during flight. We estimate the in-band performance down to 0.14 +/- 0.08 second of arc.
The redesigned payload of the Multi-Spectral Solar Telescope Array (MSSTA), the MSSTA II, was successfully flown on November 3, 1994. The multilayer mirrors used in the normal incidence optical systems of the MSSTA II are efficient reflectors for soft x-ray/extreme ultraviolet (EUV) radiation at wavelengths that satisfy the Bragg condition, thus allowing a narrow band of the soft x-ray/EUV spectrum to be isolated. When applied to solar observations the temperature response of an optical system is quite sensitive to telescope bandpass because of the high density of lines in the coronal spectrum. We have designed a set of thin foil filters in conjunction with our multilayer optics to eliminate contaminant lines and specular reflectivity, thus enhancing the temperature diagnostic capabilities of our instruments. Extensive measurements have recently been carried out on the thin foil filters at the Stanford Synchrotron Radiation Laboratory. We describe here the design and performance of thin foil filters developed for the MSSTA II.
KEYWORDS: Space telescopes, Iron, Telescopes, Solar processes, Coronagraphy, Image resolution, Spatial resolution, Temperature metrology, Reflector telescopes, Solar telescopes
The Multi Spectral Solar Telescope Array (MSSTA) is a rocket borne observatory that utilizes an array of multi-layer and interference film coated telescopes to observe the solar atmosphere from the chromosphere to the corona, over a broad spectral range (VUV - soft x rays). The MSSTA is continuously evolved to incorporate new instruments, and to improve its ability to investigate specific topics related to the structure and dynamics of the solar atmosphere. We describe chromospheric and coronal observations recorded during the second flight of the MSSTA on November 3, 1994 at 1915 UT.
The Multi-Spectral Solar Telescope Array II (MSSTA II), a rocket-borne solar observatory, was successfully flown on November 3, 1994 obtaining solar images in multiple XUV and FUV bands with an array of compact multilayer telescopes. Extensive measurements have recently been carried out on some of the multilayer telescopes at the Stanford Synchrotron Radiation Laboratory. These measurements are the first high spectral resolution calibrations of newly introduced MSSTA II instruments and instruments with lambda0 less than 130 angstrom. Previous measurements and/or calculations of telescope throughputs have been confirmed with greater accuracy. Results are presented on Mo/Si multilayer bandpasses, and multilayer bandpass changes with time.
The Multi-Spectral Solar Telescope Array, a rocket-borne solar observatory, was successfully flown in May, 1991, obtaining solar images in eight XUV and FUV bands with 12 compact multilayer telescopes. We report on recent measurements of the performance of multilayer coated mirrors for the Multi Spectral Solar Telescope Array, carried out at the Stanford Synchrotron Radiation Laboratory.
The Multi-Spectral Solar Telescope Array (MSSTA), a rocket-borne solar observatory, was successfully flown in May, 1991, obtaining solar images in eight XUV and FUV bands with 12 compact multilayer telescopes. Extensive measurements have recently been carried out on the multilayer telescopes and thin film filters at the Stanford Synchrotron Radiation Laboratory. These measurements are the first high spectral resolution calibrations of the MSSTA instruments. Previous measurements and/or calculations of telescope throughputs have been confirmed with greater accuracy. Results are presented on Mo/Si multilayer bandpass changes with time and experimental potassium bromide and tellurium filters.
Multilayer optics operated at normal incidence offer a powerful new technology for the study of the solar spectrum in the XUV. The spectra of most cosmic X-ray sources are strongly extinguished at wavelengths above 40 A due to absorption and scattering by interstellar grains. We describe a number of configurations which allow multilayer optics to be used at nonnormal angles of incidence in conjunction with grazing incidence optics to analyze the spectra of cosmic X-ray sources in the wavelength interval between 1.5 and 40 A. These optical configurations utilize both multilayer mirrors and gratings, and permit the efficient observation of extended sources using stigmatic spectrographs. The response of the instruments described to typical cosmic X-ray sources is also discussed.
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