Paul F. X. Boerner

High resolution imaging with multilayer telescopes: resolution performance of the MSSTA II telescopes

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 (44 to 1550 Aa) of the solar atmosphere. These spectroheliograms were recorded on specially fabricated XUV and FUV 70-mm Kodak film. Rocket launches of this instrument payload took place in 1991 (MSSTA I) and 1994 (MSSTA II) at the White Sands Missile Test Range in New Mexico, sponsored by the National Aeronautics and Space Administration (NASA) sounding rocket experiment program. Immediately prior to the 1994 launch, visible light focusing tests 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 arcsec at visible wavelengths. Based on these measurements, we calculate an upper bound to the focusing errors that incorporate the sum of all uncorrelated system focus 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 11 of 19 MSSTA II telescopes--having negligible figures of focus errors in comparison to the corresponding visible diffraction limits--performed atmorexa0» sub arcsecond resolution at their operational FUV/EUV/XUV wavelengths during flight. We estimate the in-band performance down to 0.14{+-}0.08 arcsec. (c) 2000 Society of Photo-Optical Instrumentation Engineers.«xa0less

INTERNETWORK CHROMOSPHERIC BRIGHT GRAINS OBSERVED WITH IRIS AND SST

The Interface Region Imaging Spectrograph (IRIS) reveals small-scale rapid brightenings in the form of bright grains all over coronal holes and the quiet Sun. These bright grains are seen with the IRIS 1330, 1400, and 2796 A slit-jaw filters. We combine coordinated observations with IRIS and from the ground with the Swedish 1 m Solar Telescope (SST) which allows us to have chromospheric (Ca II 8542 A, Ca II H 3968 A, Hα, and Mg II k 2796 A) and transition region (C II 1334 A, Si IV1403 A) spectral imaging, and single-wavelength Stokes maps in Fe I 6302 A at high spatial ( uf0b2 0 .3 3), temporal, and spectral resolution. We conclude that the IRIS slit-jaw grains are the counterpart of so-called acoustic grains, i.e., resulting from chromospheric acoustic waves in a nonmagnetic environment. We compare slit-jaw images (SJIs) with spectra from the IRIS spectrograph. We conclude that the grain intensity in the 2796 A slit-jaw filter comes from both the Mg II k core and wings. The signal in the C II and Si IV lines is too weak to explain the presence of grains in the 1300 and 1400 A SJIs and we conclude that the grain signal in these passbands comes mostly from the continuum. Although weak, the characteristic shock signatures of acoustic grains can often be detected in IRIS C II spectra. For some grains, a spectral signature can be found in IRIS Si IV. This suggests that upward propagating acoustic waves sometimes reach all the way up to the transition region.

The high-resolution lightweight telescope for the EUV (HiLiTE)

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 NASAs Solar Dynamics Observatory (SDO). This new instrument technology thus serves as a path finder to a post-AIA, Explorer-class missions.

High-resolution imaging with multilayer telescopes: resolution performance of the MSSTA II telescopes

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.

Chromospheric/coronal spectroheliograph

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.

SDO-AIA mirror performance

We will discuss the design, specification, construction, and assembly of the 4 mirror systems that make up the Solar Dynamics Observatory (SDO) Atmospheric Imaging Array (AIA). We will include the extensive imaging performance measurements made on the mirror throughout the post-polishing mirror processing period.

Sounding rocket mission to study the solar soft x-ray and EUV emission using transition-edge sensor technology

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.