Wolter Type Research Articles

The Rosat mission

The primary scientific objective of the ROSAT mission is to perform the first all sky survey with an imaging X-ray telescope leading to an improvement in sensitivity by several orders of magnitude compared with previous surveys. Consequently a large number of new sources (> 105) will be discovered and located with an accuracy of 1 arcmin. After completion of the survey which will take about half a year the instrument will be used for detailed observations of selected targets. The X-ray telescope consists of a fourfold nested Wolter type I mirror system with 80 cm aperture and 240 cm focal length, and three focal plane detectors. In the baseline version these will be imaging proportional counters (0.1 – 2 keV) providing a field of view of 20 × 20.

Comparison Of Wolter I And Kirkpatrick-Baez X-Ray Optics For A Spacelab LAMAR Facility

An x-ray astronomical observatory called the LAMAR, utilizing multiple grazing incidence x-ray telescopes for high sensitivity observations, is being considered by NASA for a Spacelab facility. A LAMAR utilizing Wolter Type I x-ray optics figured by diamond turning is described and its performance compared with a similar facility involving x-ray optics of Kirkpatrick-Baez design. Effective areas, imaging properties, and relative sensitivities of these two LAMAR facilities have been calculated with the aid of computer ray tracing codes. We conclude that the two optical designs provide comparable effective areas. Therefore, the ability to achieve the highest possible angular resolution within cost constraints will be decisive in the choice of x-ray optics for the LAMAR.

<title>High Performance Extreme Ultraviolet (EUV) Telescope</title>

A nested array of Wolter type II grazing incidence telescopes for use in the extreme ultraviolet is described. It is demonstrated by an example that it is possible to design the array with all subsystems having matching focal lengths, matching field radii, the same grazing angle at the primary elements, and only slightly different grazing angles on the secondary elements.

Properties of a transmission grating behind a grazing incidence telescope for cosmic x-ray spectroscopy

Third-order aberrations are discussed of a transmission grating positioned behind a Wolter type I telescope, using Fermat's principle. We describe the conditions required to obtain a coma-free grating. The performance of a grating spectrometer for cosmic x-ray spectroscopy is discussed in some detail.

Variation of energy throughput with off-axis angle for the S056 x-ray telescope

The S056 solar X-ray telescope, a paraboloidal-hyperboloidal Wolter type I instrument, was used in the Skylab solar observatory to photograph the sun in various soft X-ray wavelength bands. It is necessary to know how the energy throughput of the telescope varies as a function of off-axis angle at various wavelengths in order to compare the relative intensities of solar X-ray emission from various areas of the sun captured on the same photographic frame.

The GSFC EUV and X-ray spectroheliograph on OSO-7

The Goddard Space Flight Center instrument carried on the pointed section of the OSO-7 satellite is described. This instrument contains: An extreme ultraviolet spectroheliograph using glancing incidence optics of Wolter's Type II to focus the Sun's light on the entrance slit of a concave grating spectrometer; an auxiliary Hα system; two X-ray spectroheliographs using mechanical collimators for spatial resolution and Ross filters to isolate spectral bands of interest, and a flare polarimeter operating in the 15–40 keV X-ray region. These subsystems may be operated in a number of modes which, when combined with the spacecraft modes, give the instrument great flexibility for making solar observations. Representative results from each of the subsystems are presented.

Evidence for the 300-SECOND Oscillation from OSO-7 Extreme-Ultraviolet Observations

The detection and significance of 300-second oscillations in extreme-ultraviolet lines formed in the solar transition region are discussed. Detection was accomplished with the Goddard extreme-ultraviolet spectroheliograph and the Wolter type II grazing-incidence telescope. The Cooley-Tukey algorithm was used to compute the required Fourier transform of the discrete data. Presence of significant power in the observed lines around 262 sec seems to be the first observational evidence that periodic waves in this frequency range persist at heights where local kinetic temperatures are close to one million degrees K. The observed horizontal extent of the wave fronts appears to be much greater than the extent of coherent oscillating elements at chromospheric heights. Several implications are stated for the problem of heating of the transition region and low corona.

Glancing Incidence Optics for X-Ray and Ultraviolet Astronomy

Glancing incidence telescopes of the kind first described by Wolter have now been physically realized, so that it is now possible to obtain high resolution images of celestial objects at all wavelengths greater than about 3 Å. In this paper we shall describe two such instruments: the GSFC-MSFC X-ray telescope for the Apollo telescope mount uses Wolter type 1 optics and is capable of forming images of the sun in the 8–70 Å region with spatial resolution of the order of one arc second. The GSFC extreme ultraviolet spectroheliometer for OSO H uses type 2 optics and can obtain images of the Sun in spectral lines in the 170–400 Å region with a spatial resolution of about ten arc seconds. Theoretical (ray trace) and laboratory data on these systems will be presented.

Optical Design of Glancing Incidence Extreme Ultraviolet Telescopes

Glancing incidence telescope designs employing surfaces of revolution and of the same geometry as the Wolter type 2 telescope (a concave paraboloid followed by a confocal convex hyperboloid) are investigated for primarily solar physics applications in the spectral region greater than 100 A. The optical properties of the telescopes are evaluated in terms of minimum spot size and flattened focal surface as a function of optical acceptance (throughput) and folding ratio (physical length of the telescope/effective focal length). One meter focal length systems with full fields of 0.8 deg, throughputs of 15 x 10(-4) sr and 30 x 10(-4) sr, and maximum grazing angles of 13 deg are shown to exhibit optimum imaging properties for a folding ratio on the order of 0.85.

Optical Design of a Glancing Incidence X-ray Telescope

The optical design of a Wolter type 1 glancing incidence x-ray telescope for the wavelength region 6-100 A is described. The theoretical performance of the instrument is evaluated by ray tracing. The results of laboratory and rocket flight tests on a prototype instrument are briefly described.

A glancing incidence solar telescope for the soft x-ray region

This paper describes the instrumentation of an Aerobee rocket (NASA 4.95 GS) which was launched from White Sands Missile Range on May 20th 1966, to observe the Sun in the soft X-ray region. The experiment package, which was pointed at the sun by a control system stabilized about all three axes, carried two Wolter type I glancing incidence telescopes to photograph the sun in wavelength regions (determined by bandpass filters) between 3 and 75 Å, and two proportional counters to obtain flux data and rough spectral shapes in the regions 2–11 Å and 8–20 Å. The spatial resolution obtained was about 20 arc seconds. Limb brightening and polar darkening are very pronounced at the longer wavelengths. A tuft of emission was observed at the North Pole in addition to an arch-like structure on the NW limb. Several of the photographs are presented, and some preliminary results are discussed.