Engineering topics

Hoover, Richard B.

Publications and source records attributed to Hoover, Richard B..

170 records · Page 10

NASA NTRS1989

Design and analysis of optical systems for the Stanford/MSFC Multi-Spectral Solar Telescope Array

This paper reports on the design and the theoretical ray trace analysis of the optical systems which will comprise the primary imaging components for the Stanford/MSFC Multi-Spectral Solar Telescope Array (MSSTA). This instrument is being developed for ultra-high resolution investigations of the sun from a sounding rocket. Doubly reflecting systems of sphere-sphere, ellipsoid-sphere (Dall-Kirkham), paraboloid-hyperboloid (Cassegrain), and hyperboloid-hyperboloid (Ritchey-Chretien) configurations were analyzed. For these mirror systems, ray trace analysis was performed and through-focus spot diagrams, point spread function plots, and geometrical and diffraction MTFs were generated. The results of these studies are presented along with the parameters of the Ritchey-Chretien optical system selected for the MSSTA flight. The payload, which incorporates seven of these Ritchey-Chretien systems, is now being prepared for launch in late September 1989.

Hadaway, James B.↗

NASA NTRS1988

Soft X-ray images of the solar corona with a normal-incidence Cassegrain multilayer telescope

High-resolution images of the sun in the soft X-ray to EUV regime have been obtained with normal-incidence Cassegrain multilayer telescopes operated from a sounding rocket in space. The inherent energy-selective property of multilayer-coated optics allowed distinct groups of emission lines to be isolated in the solar corona and the transition region. The Cassegrain telescopes provided images in bands centered at 173 and 256 A. The bandpass centered at 173 A is dominated by emission from the ions Fe IX and Fe X. This emission is from coronal plasma in the temperature range (8-14) x 10 to the 6th K. The images have angular resolution of about 1.0-1.5 arcsec and show no degradation because of X-ray scattering. Many features of coronal structure, including magnetically confined loops of hot plasma, coronal plumes, polar coronal holes, faint structures on the size scale of supergranulation and smaller, and features due to everlying cool prominences are visible in the images. The density structure of polar plumes, which are thought to contribute to the solar wind, has been derived from the observations out to 1.7 solar radii.

Walker, Arthur B. C., Jr.↗

NASA NTRS1988

Soft X-ray/extreme ultraviolet images of the solar atmosphere with normal incidence multilayer optics

High-resolution images of the sun in the soft-X-ray/XUV range have been obtained with normal-incidence multilayer coated optics (MCOs) during a sounding-rocket flight on October 23, 1987 from White Sands. MCOs were used in two Cassegrain telescopes, as off-axis primary mirrors, and as tertiary mirrors operating with a Wolter-Schwarzschild (WS) grazing-incidence mirror. The inherent energy-selective property of MCOs allowed distinct groups of emission lines to be isolated in the solar corona and the transition region. Images were recorded at 173 and 256 A with the Cassegrain telescopes, at 256 A with a Herschelian telescope, and at 44, 173, and 256 A with the WS hybrid telescope. In addition, soft-X-ray images in the 8-18-A bandpass were obtained at the prime focus of the WS optics. The images show many features of the solar corona and transition region, including magnetically confined loops of hot solar plasma, coronal plumes, polar coronal holes, supergranulation, and features associated with overlying cool prominences.

Lindblom, Joakim F.↗

NASA NTRS1988

Design of an imaging microscope for soft X-ray applications

An imaging soft X-ray microscope with a spatial resolution of 0.1 micron and normal incidence multilayer optics is discussed. The microscope has a Schwarzschild configuration, which consists of two concentric spherical mirrors with radii of curvature which minimize third-order spherical aberration, coma, and astigmatism. The performance of the Stanford/MSFC Cassegrain X-ray telescope and its relevance to the present microscope are addressed. A ray tracing analysis of the optical system indicates that diffraction-limited performance can be expected for an object height of 0.2 mm.

Hoover, Richard B.↗

NASA NTRS1986

Hybrid X-ray telescope systems

It has been known for some time that glancing incidence X-ray optics have sharply peaked point response functions. The spatial resolution of Wolter X-ray telescope systems is frequently limited by the performance characteristics of the X-ray detector rather than by the optics, even when high resolution detectors such as photographic emulsions are used. This problem becomes even more severe when it is desirable to take advantage of the high sensitivity and broad wavelength response afforded by modern solid state detectors such as charge coupled devices or multi-anode microchannel arrays. Results of theoretical investigations of methods for increasing the telescope plate scale by the use of glancing incidence hyperboloid/ellipsoid X-ray microscope optics and normal incidence contoured layered synthetic microstructure optics for coupling the Wolter mirrors to the detector are reported. The relative merits of the different hybrid X-ray telescope systems which result will be discussed. Considerations will be made concerning applications of these systems to high resolution imagery and spectroscopy of astronomical X-ray/XUV sources.

Shealy, David L.↗

NASA NTRS1986

Multilayer X-ray imaging systems

An assessment of the imaging properties of multilayer X-ray imaging systems with spherical surfaces has been made. A ray trace analysis was performed to investigate the effects of using spherical substrates (rather than the conventional paraboloidal/hyperboloidal contours) for doubly reflecting Cassegrain telescopes. These investigations were carried out for mirrors designed to operate at selected soft X-ray/XUV wavelengths that are of significance for studies of the solar corona/transition region from the Stanford/MSFC Rocket X-Ray Telescope. The effects of changes in separation of the primary and secondary elements were also investigated. These theoretical results are presented as well as the results of ray trace studies to establish the resolution and vignetting effects as a function of field angle and system parameters.

Shealy, David L.↗

NASA NTRS1985

Glancing incidence X-ray optics for solar X-ray astronomy

Glancing incidence X-ray optics have been developed into a highly valuable tool for high-resolution investigations of the sun in the X-ray/XUV regime. A brief overview of the development of X-ray optics technology is presented. Techniques currently under study for increasing the plate scale and improving the off-axis performance of future X-ray telescopes for solar X-ray astronomy are briefly discussed.

Hoover, Richard B.↗

NASA NTRS1985

Photographic film as a detector for solar X-ray/XUV astronomical applications

The characteristics of several films as detectors for solar soft X-ray (3-100 A) and XUV (100-600 A) radiation are discussed. The properties of soft-X-ray-sensitive films like the SO-212 make them useful for the glancing-incidence X-ray telescopes. Used for the MSFC X-Ray Telescope during the Skylab mission (at the wavelengths of 8.34 and 15.4 A), the SO-212 film functioned as a photon detector, achieving spatial resolution of 2.2 arc sec. Other high-resolution soft-X-ray-sensitive films include SO-242 and 101-07. For XUV detection, the SC-5, SC-7, 104-07, and 101-07 films are recommended.

Hoover, Richard B.↗