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At least 1,441 records · Page 80
All sourcesNASA NTRSDOE OSTI
NASA NTRS1986

Optical system design, analysis, and production for advanced technology systems; Proceedings of the Meeting, Innsbruck, Austria, Apr. 15-17, 1986

The present conference considers topics in the fields of optical systems design software, the design and analysis of optical systems, illustrative cases of advanced optical system design, the integration of optical designs into greater systems, and optical fabrication and testing techniques. Attention is given to an extended range diffraction-based merit function for lens design optimization, an assessment of technologies for stray light control and evaluation, the automated characterization of IR systems' spatial resolution, a spectrum of design techniques based on aberration theory, a three-field IR telescope, a large aperture zoom lens for 16-mm motion picture cameras, and the use of concave holographic gratings as monochomators. Also discussed are the use of aspherics in optical systems, glass choice procedures for periscope design, the fabrication and testing of unconventional optics, low mass mirrors for large optics, and the diamond grinding of optical surfaces on aspheric lens molds.

Fischer, Robert E.↗
NASA NTRS1987

Moire interferometry, 1986

Current capabilities of moire interferometry are described. Several examples illustrate this whole-field optical technique for measurements of in-plane displacements. Sensitivity corresponds to moire measurements with gratings of 2400 lines/mm. The examples are taken from studies of composite members, material anomalies, plasticity, joints, micromechanics and strain concentrations. The abundance of high-sensitivity displacement information permits calculation of normal strains and shear strains in the field, including critical zones of very high gradients.

Post, D.↗
NASA NTRS1987

Exploiting the IR: Solar and stellar spectroscopy in the IR

Recent instrumental advances have provided the capability to perform high resolution spectroscopy, in the thermal infrared region of the solar spectrum, with high sensitivity. The 8 to 12 micron region was extensively observed using Fourier transform (FTS) and laser heterodyne techniques. The continuous opacity of the solar atmosphere, due to H(-), increases with wavelength in the infrared region longward of 1.6 microns. Consequently thermal infrared observations probe the upper photosphere, and give an insight into the dynamics and structure of this region. The most notable spectral features in the 10 micron window include pure rotation lines of OH, and emission lines due to high-n states in MgI and AlI. The high-n lines due to MgI and AlI are important to solar and stellar physics because of their very large Zeeman sensitivity. The recent development of a cryogenic grating postdispenser for the FTS has allowed low-noise solar observations of these lines in 90 seconds. Limited mapping of the lines in a sunspot penumbra was performed, and gives information of the structure of the penumbral magnetic field. Although the MgI lines were detected in red giant spectra, instrumental sensitivity is not yet sufficient to see them in stars where significant magnetic fields are expected.

Deming, Drake↗
NASA NTRS1987

A geostationary imaging spectrometer TOMS instrument

One design for a geostationary Total Ozone Mapping Spectrometer (TOMS) with many desirable features is an imaging spectrometer. A preliminary study makes use of a 0.25 m Czerny-Turner spectrometer with which the Earth is imaged on a charge-coupled device (CCD) in dispersed light. The wavelength is determined by a movable grating which can be set arbitrarily by ground control. The signal integration time depends on wavelength but this system allows arbitrary timing by command. Special circumstances such as a requirement to track a low-lying sulfur dioxide cloud or a need to discriminate high level ozone from total ozone at midlatitudes could be obtained by adding a particular wavelength to the normally pre-programmed time sequence. The incident solar irradiance is measured by deploying a diffuser plate in the field of view. Individual detector elements correspond to scene elements in which the several wavelengths are serially sampled and the Earth radiance is compared to the incident sunlight. Thus the problem of uncorrelated drift of multiple detectors is removed.

Krueger, Arlin J.↗
NASA NTRS1987

Hard- and software problems of spaced meteor observations by optical electronics

An optical electronic facility is being used for meteor observations along with meteor radars and astronomical TV. The main parts of the facility are cameras using UM-92 optical electronic image tubes. The three cascade optical electronic image tube with magnetic focusing has a 40 mm cathode and resolution in the center of up to 30 pairs of lines/mm. The photocathode is of a multislit S-20 type. For meteor spectra observations, replica gratings of 200 and 300 lines/mm are used as the dispersive element.

Shafiev, R. I.↗
NASA NTRS1987

Backscatter from a periodic rough surface at near grazing incidence

The effect of periodic surface roughness on the radar cross section (RCS) was studied. The surface roughness was formed by a small sinusoidal variation in a planar surface. RCS measurements were obtained for two different sinusoidal variations near grazing incidence for both principle polarizations. Significant grating lobes were observed in the measurements which directly correspond to the roughness characteristics. A physical optics solution was generated and compared to the measurements with reasonable agreement.

Dominek, A. K.↗
NASA NTRS1988

High resolution infrared absorption spectra of various trace gases present in the upper atmosphere of the Earth

The objective of NASA Grant NsG 7473 was to obtain and analyze high resolution infrared absorption spectra of various trace gases present in the Earth's upper atmosphere. The goal of the spectral analysis was to obtain values of absorption line strengths, widths and frequencies of sufficient accuracy for use in upper atmosphere trace gas monitoring. During the early phase of the grant, high resolution spectra were obtained from two instruments. One was the 0.02/cm resolution vacuum grating spectrometer at the Florida State University and the other was the 0.01/cm resolution Fourier transform spectrometer at the McMath solar telescope at the Kitt Peak Observatory. Using these instruments, a considerable amount of spectra of methane and hydrogen peroxide were obtained and analyzed. During the latter years of the project, data taking was halted while efforts were devoted to building a new 0.0025/cm resolution vacuum Fourier transform spectrometer. Progress during this phase of the grant then became greatly slowed due to a lack of suitable graduate students in the program. However, the instrument was completed and brought to the point of producing interferograms.

Hunt, Robert H.↗
NASA NTRS1988

A very wide frequency band pulsed/IF radar system

A pulsed/IF radar for compact range radar cross section measurements has been developed which converts RF returns to a fixed IF, so that amplification and grating may be performed at one frequency. This permits the use of components which have optimal performance at this frequency which results in a corresponding improvement in performance. Sensitivity and dynamic range are calculated for this system and compared with our old radar, and the effect of pulse width on clutter level is also studied. Sensitivity and accuracy tests are included to verify the performance of the radar.

Jones, D. N.↗
NASA NTRS1987

High resolution absorption cross-sections and band oscillator strengths of the Schumann-Runge bands of oxygen at 79 K

Cross sections of O2 at 79 K have been obtained from photoabsorption measurements at various pressures throughout the wavelength region 179.3-198.0 nm with a 6.65-m photoelectric scanning spectrometer equipped with a 2400-lines/mm grating and having an instrumental width (FWHM) of 0.0013 nm. The measured absorption cross sections of the Schumann-Runge bands (12,0) through (2,0) are independent of the instrumental width. The measured cross-sections are presented graphically here and are available at wavenumber intervals of about 0.1/cm as numerical compilations stored on magnetic tape from the National Space Science Data Center, NASA/Goddard. Band oscillator strengths of these bands have been determined by direct numerical integration of the measured cross sections.

Yoshino, K.↗
NASA NTRS1986

Calibration of a 1 meter diameter normal incidence extreme ultraviolet telescope/spectrometer

A 1-meter normal incidence telescope, with a normal incidence concave diffraction grating spectrometer at its focus, has been developed. The instrument's spectral coverage is 350 to 1150A with a spectral resolution of 5A and a peak effective area of 6 sq cm at 500A. The instrument was launched on an Aries sounding rocket on November 27, 1983 in an effort to determine the hydrogen and helium abundance in the local interstellar medium. A description of this instrument, with the primary emphasis on the methods used to calibrate it, is presented.

Jelinsky, Patrick↗
NASA NTRS1986

The soft X-ray/EUV calibration facility at the University of Colorado

The components of the calibration facility at the University of Colorado are described. The system is capable of analyzing the performance of optical components in the wavelength range from 2.7 to 2500 A. The system uses two light sources: a water-cooled hollow cathode gas discharge source and a soft X-ray source. The 2.2-m grazing incidence monochrometer, slits, large chamber, and computer-controlled manipulator are examined. The NBS aluminum oxide photodiode, a flowing gas proportional counter, and an imaging microchannel plate device are employed to detect the light. The optics, detectors, and data acquisition system are computer controlled. The facility is applicable for evaluating the performance of diffraction gratings, multilayer mirrors, reflective coatings, spectrographs, surface roughness scattering, and absolute detector efficiencies. Examples demonstrating the capabilities of the facility and a diagram of the facility are presented.

Windt, David L.↗
NASA NTRS1987

Fabrication of imaging X-ray optics

The design, fabrication, and performance of optics for X-ray astronomy and laboratory applications are described and illustrated with diagrams, drawings, graphs, photographs, and sample images. Particular attention is given to the Wolter I telescope developed for spectroscopic observation of 8-30-A cosmic X-ray sources from a rocketborne X-ray Objective Grating Spectrometer; this instrument employs three nested paraboloid-hyperboloid mirrors of 5083 Al alloy, figured by diamond turning and covered with a thin coating of acrylic lacquer prior to deposition of a 40-nm-thick layer of Sn. In calibration tests at NASA Marshall, the FWHM of the line-spread function at 1.33 nm was found to be 240 microns, corresponding to 21 arcsec. Also presented are the results of reflectivity measurements on C and W multilayers sputtered on Si and fusion glass substrates.

Catura, R. C.↗
NASA NTRS1987

The advanced X-ray astrophysics facility - An overview

This paper presents an overview of NASA's Advanced X-Ray Astrophysics Facility (AXAF), which is planned for launch in the 1990s and is expected to operate in space for at least 15 years. The design of the X-ray telescope is discussed and the instruments that may fly at the start of the AXAF mission, the principal investigator of each instrument, and the instrument performance parameters are listed. The AXAF instruments will include low-energy and high-energy transimission gratings, a Bragg crystal spectrometer, CCD imagers, an X-ray calorimeter, and a microchannel plate imager. The long lifetime of the AXAF will make it possible to follow up on the HEAO-2/Einstein results, the more recent X-ray observations performed by European and Japanese satellites, and the future ROSAT all-sky survey. The long lifetime of the AXAF, together with the servicing capability that will be offered by the Space Station, will also provide the opportunity of incorporating other instruments into the observatory.

Weisskopf, Martin C.↗
NASA NTRS1987

The AXAF CCD Imaging Spectrometer Experiment (ACIS)

The ACIS experiment consists of an array of charge coupled device (CCD) chips placed at the focus of the AXAF mirror assembly. The instrument offers a powerful combination of the best qualities of the entire generation of Einstein Observatory detectors. The pixel size is well matched to the resolution of the telescope, while the high quantum efficiency nondispersive spectroscopy capability means that every object imaged will produce a moderate resolution spectrum. In conjunction with the objective gratings the energy resolution increases to 1000 with a loss of efficiency of only 50 percent. While the great capability of ACIS will naturally make it attractive for a wide range of AXAF investigations, ACIS has a particular advantage in fields where it can simultaneously acquire imaged spectra of many objects. These include compact star clusters, star formation regions, the nuclear regions of nearby galaxies, entire galaxies in the Virgo Cluster and the entire Coma Cluster.

Nousek, J. A.↗
NASA NTRS1987

The MIT spectroscopy investigations on AXAF and the study of supernova remnants

The MIT High Resolution X-Ray Spectroscopy experiment on the AXAF, which will study physical conditions in celestial sources by means of detailed measurements of emission and absorption features in their spectra, involves two complementary dispersive instruments: Bragg Crystal Spectrometer (BCS) and High Energy Transmission Grating (HETG). This paper discusses the principles of operation of BCS and HETG and the results that will be obtained by these instruments. Measurements of individual line strengths obtained by the AXAF spectrometers will allow the application of plasma diagnostic techniques to a study of the detailed physical conditions in celestial objects, particularly in the optically thin plasma of supernova remnants, which is particularly well suited to the application of plasma diagnostics.

Canizares, C. R.↗
NASA NTRS1988

X-ray spectral models of Galactic bulge sources - The emission-line factor

Current difficulties in finding unique and physically meaningful models for the X-ray spectra of Galactic bulge sources are exacerbated by the presence of strong, variable emission and absorption features that are not resolved by the instruments observing them. Nine Einstein solid state spectrometer (SSS) observations of five Galactic bulge sources are presented for which relatively high resolution objective grating spectrometer (OGS) data have been published. It is found that in every case the goodness of fit of simple models to SSS data is greatly improved by adding line features identified in the OGS that cannot be resolved by the SSS but nevertheless strongly influence the spectra observed by SSS.

Vrtilek, S. D.↗
NASA NTRS1987

Photon noise and constant-volume operators

In a previous paper, a class of constant volume (CV) operators designed to maximize spatial resolution in the presence of photon noise was introduced. In this paper, the statistical properties are derived of the output images created by CV operators applied to photon-noisy versions of input images consisting of edges, spots, and gratings. The results are used to calculate the input image parameters that would permit any test image to be discriminated from a uniform field with a given level of reliability and consequently to compare the predictions of a CV operator model with psychophysical data. These results also allow the potential usefulness of CV operators in artificial image processing applications to be assessed.

Yellott, John I., Jr.↗
NASA NTRS1987

Rocket ultraviolet observations of Comet Halley

Ultraviolet observations of Comet Halley have been obtained in February and March, 1986 with two instrument payloads, one with the Faint Object Telescope and one with a direct imaging electrographic Schmidt camera and an objective grating spectrograph. The observations include spectroscopic imagery in the 1200-200 A wavelength range and imagery of the comet in hydrogen Lyman-alpha (1216 A) radiation. The present observations have been reduced to intensity contour plots in the different emission wavelengths, and production rates are given for the emitting species H, C, O, S, and CO.

Carruthers, George R.↗