Phillip C. Baker

Multi-Spectral Solar Telescope Array II: soft x-ray EUV reflectivity of the multilayer mirrors

We have developed seven compact soft x-ray/EUV (XUV) multilayer- coated and two compact FUV interference-film-coated Cassegrain and Ritchey-Chretien telescopes for a rocket-borne observatory, the Multi-Spectral Solar Telescope Array. We report here on extensive measurements of the efficiency and spectral band pass of the XUV telescopes carried out at the Stanford Synchrotron Radiation Laboratory.

Polarimetry of H-Lyman α for coronal magnetic field diagnostics

We discuss and analyze the possible sources of observational and instrumental uncertainty that can be encountered in measuring magnetic fields of the solar corona through polarimetric observations of the Hanle effect of the coronal Ly-alpha line. The Hanle effect is the modification of the linear polarization of a resonantly scattered line, due to the presence of a magnetic field. Simulated observations are used to examine how polarimetric measurements of this effect are affected by the line-of-sight integration, the electron collisions, and the Ly-alpha geocorona. We plan to implement the coronal magnetic field diagnostics via the Ly-alpha Hanle effect using an all-reflecting Ly-alpha coronagraph/polarimeter (Ly-alphaCoPo) which employs reflecting multilayer mirrors, polarizers, and filters. We discuss here the requirements for such an instrument, and analyze the sources of instrumental uncertainty for polarimetric observations of the coronal Ly-alpha Hanle effect. We conclude that the anticipated polarization signal from the corona and the expected performance of the Ly-alphaCoPo instrument are such that the Ly-alpha Hanle effect method for coronal field diagnostics is feasible.

Stray light analysis of a reflecting UV Coronagraph/Polarimeter with multilayer optics

An analysis is presented of the stray light expected in a Coronagraph/Polarimeter operating at the H I Lyman (alpha) (Ly-(alpha) ) line ((lambda) 121.6 nm) and utilizing multilayer interference film optics and ultrasmooth substrates (i.e., rms-smoothness Optics & Photonics OP 40 1993-07-11|1993-07-16 SPIEs 1993 International Symposium on Optics, Imaging, and Instrumentation SD93 51144 San Diego, CA, United States X-Ray and Ultraviolet Polarimetry 2010 Astronomical XUV Polarimetry II 2

Performance of compact multilayer coated telescopes at soft X-ray/EUV and far ultraviolet wavelengths

We have developed compact soft x-ray/EUV (XUV) and farultraviolet (FUV) multilayer coated telescopes for the study of the solar chromosphere corona, and corona/solar wind interface. Because they operate at short wavelengths (~40 < ? < 1550 A), the modest apertures of 40 to 127 mm allow observations at very high angular resolution (0.1 to 0.7 arcsec). In addition to permitting traditional normal incidence optical configurations such as Cassegrain, Ritchey-Chretien, and Herschelian to be used at XUV wavelengths, multilayer coatings also allow a narrow wavelength band (?/?? ~30 to 100) to be selected for imaging. The resuIting telescopes provide a very powerful and flexible diagnostic instrument for the study of both the fine scale structure of the chromosphere/ corona interface and the large scale structure of the corona and corona/ solar wind interface. In previous papers we described a new solar rocket payload, the Multi-Spectral Solar Telescope Array (MSSTA), composed of 17 of these compact telescopes. In this paper we report on the performance of the seven MSSTA Ritchey-Chretien telescopes.

Design and fabrication of the all-reflecting H-Lyman alpha coronagraph/polarimeter

We have designed, analyzed, and are now fabricating an All-Reflecting H-Lyman-alpha Coronagraph/Polarimeter for solar research. This new instrument operates in a narrow bandpass centered at 215.7 A - the neutral hydrogen Ly-alpha line. It is shorter and faster than the telescope which produced solar Ly-alpha images as a part of the MSSTA payload that was launched on May 13, 1991. The Ly-alpha line is produced and linearly polarized in the solar corona by resonance scattering, and the presence of a magnetic field modifies this polarization according to the Hanle effect. The Lyman-alpha Coronagraph/Polarimeter instrument has been designed to measure coronal magnetic fields by interpreting, via the Hanle effect, the measured linear polarization of the coronal Ly-alpha line. Ultrasmooth mirrors, polarizers, and filters are being flow-polished for this instrument from CVD silicon carbide substrates. These optical components will be coated using advanced induced transmission and absorption thin film multilayer coatings to optimize the reflectivity and polarization properties at 1215.7 A. We describe some of the solar imaging results obtained with the MSSTA Lyman-alpha coronagraph. We also discuss the optical design parameters and fabrication plans for the All-Reflecting H-Lyman-alpha Coronagraph/Polarimeter.

High-resolution imaging with multilayer soft x-ray, EUV, and FUV telescopes of modest aperture and cost

The development of multilayer reflective coatings now permits soft X-ray, EUV and FUV radiation to be efficiently imaged by conventional normal incidence optical configurations. Telescopes with quite modest apertures can, in principle, achieve images with resolutions which would require apertures of 1.25 meters or more at visible wavelengths. The progress is reviewed which has been made in developing compact telescopes for ultra-high resolution imaging of the sun at soft X-ray, EUV and FUV wavelengths, including laboratory test results and astronomical images obtained with rocket-borne multilayer telescopes. The factors are discussed which limit the resolution which has been achieved so far, and the problems which must be addressed to attain, and surpass the 0.1 arc-second level. The application of these technologies to the development of solar telescopes for future space missions is also described.

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.

Performance of the Multi-Spectral Solar Telescope Array. III - Optical characteristics of the Ritchey-Chretien and Cassegrain telescopes

The Multi-Spectral Solar Telescope Array (MSSTA) is a sounding rocket borne observatory for investigations of the Sun in the soft x-ray/EUV and FUV regimes of the electromagnetic spectrum. At soft x-ray wavelengths (),\ < 100 A), the MSSTA utilizes single reflection multilayer coated Herschelian telescopes. For selected wavelengths in the EUV (100 - 1000 A) the MSSTA employs five doubly reflecting, multilayer coated Ritchey-Chretien and two Cassegrain telescopes. In the FUV ()\ > 1000 A) the MSSTA utilizes two Ritchey-Chretien telescopes, with optics coated with thin film interference coatings. In this paper, we describe the interferometric alignment, testing, focusing, visible light testing, and optical performance characteristics of the Ritchey-Chretien and Cassegrain telescopes.

Fabrication and test of a wide-field H-Lyman alpha coronagraph/polarimeter

The Wide Field H-Lyman (alpha) Coronagraph/Polarimeter is currently being developed for solar research. This instrument has been designed to produce high resolution full-disk images of the Sun in a narrow bandpass centered at the neutral hydrogen Lyman (alpha) (Ly-(alpha) ) line ((lambda) 1215.7 angstroms). It has higher sensitivity and a wider field-of-view than the coronagraph which produced solar Ly-(alpha) images on May 13, 1991 during the MSSTA flight. The all-reflecting polarizers use advanced induced transmission and absorption thin film multilayer coatings to optimize the reflectivity and polarization properties at 1215.7 angstroms. We describe the instrument and discuss the current status of the fabrication of the Wide Field H-Lyman (alpha) Coronagraph/Polarimeter.

Performance of the repolished S-056 grazing incidence mirror in the MSFC AXAF test facility

The S-056 Wolter I soft x-ray mirror used originally on Skylab for x-ray observations of the Sun is still in use today. The mirror has been flow polished to a surface finish of 5 angstroms for spatial frequencies from 1 - 1000 mm-1 and has been tested in the AXAF x- ray calibration facility located at Marshall Space Flight Center, Alabama. The mirror performance was enhanced by a new polishing technique and was found to have an experimental point spread function full width half maximum of less than 1 arc second at 8.3 angstroms. No change in the figure was observed.