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At least 379 records · Page 21

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NASA NTRS1973

Identification and analysis of structures in the corona from X-ray photography

This paper summarizes the results of a program of rocket observations of the solar corona with grazing incidence X-ray telescopes. A series of five flights of a Kanigen-surfaced telescope with a few arc seconds resolution, together with the first flight of a newer telescope have resulted in the identification of six classes of coronal structures observable in the X-ray photographs. These are: active regions, active region interconnections, large loop structures associated with unipolar magnetic regions, coronal holes, coronal bright points, and the structures surrounding filament cavities. Two solar flares have been observed. The methods involved in deriving coronal temperature and density information from X-ray photographs are described and the analysis of a bright active region (McMath plage 11035) observed at the west limb on November 24, 1970 is presented as an example of these techniques.

Vaiana, G. S.↗

NASA NTRS1974

Observations of the extreme ultraviolet nightglow

An extreme ultraviolet telescope system was flown on an Aerobee 170 rocket from the White Sands Missile Range on Oct. 22, 1971. Measurements of extreme ultraviolet radiation from the night sky were made with a set of Parylene, aluminum, and tin filters behind a grazing incidence concentrator. If the aluminum and tin filter data are interpreted as being due to only the He I 584-A and He II 304-A lines, the nightglow flux at 25 deg zenith angle and 270 deg azimuth angle at 180-km altitude was I(584) = 4.4 plus or minus 1.9 R and I(304) = 1.3 plus or minus 0.5 R.

Riegler, G. R.↗

NASA NTRS1974

Design of an X-ray telescope system for an orbiting astronomical observatory

The design and construction is described of a package of X-ray telescopes launched in the NASA satellite Copernicus (OAO-3), which began stellar observations in September 1972. It contains three grazing incidence reflectors covering a range of wavelengths from 0.3 to 8 nm, and having a combined collecting area of 40.9 sq cm, with angular resolutions up to 1 minute of arc. This is believed to be the first satellite application of such reflectors in stellar X-ray astronomy. A collimated detector of wavelengths 0.1-0.3 nm has a 17.8 sq cm collecting area. A visible light star tracker detects package misalignment if this should occur.

Bowles, J. A.↗

NASA NTRS1973

Remote sensing for monitoring a water transportation project - The California Aqueduct

Land use changes were investigated on the west side of the San Joaquin Valley, California, an arid region presently importing water via the California Aqueduct, utilizing airphoto mosaics (1957), high-altitude photography (1971), and Earth Resources Technology Satellite (ERTS-1) data (1972). Attention was focused on land use characteristics for the three dates, changes which had occurred, and the sequence of land use category change. Research indicated that water importation was contributing to an overall pattern of regional change trending from an oil-producing and grazing area into a cropping region. Furthermore, the general pattern of specific category change was trending in the direction of higher economic intensity land use succession.

Estes, J. E.↗

NASA NTRS1974

Fabrication of an extreme ultraviolet glancing incidence telescope

A technique is described for use in the fabrication of glancing incidence telescopes which operate at large grazing angles (i.e., 8 to 15 degrees). Precision conic section plunge laps are used in a controlled grinding procedure to initially generate imaging surfaces which have a minimum of subsurface damage. A numerically controlled Moore Number 3 Measuring Machine is used throughout the fabrication procedure. Surface geometry accuracies on the order of one-tenth micron have been achieved.

Fleetwood, C. M.↗

NASA NTRS1974

Optical grating analyzer studies

A spectrometer was specifically designed and developed to observe grating spectra over a range of incidence angles from normal to almost grazing incidence. A unique scanning and focusing mechanism is utilized to keep the exit slit on the Rowland circle. Polarization effects in the vacuum were investigated, and efficiency measurements and spectral scans were made simultaneously with the spectrometer. Results of measurements are given. Applications of the spectrometer to the space program and to the study of contamination on optical surfaces are indicated.

Mcdonald, J. K.↗

NASA NTRS1973

Principles of cost-benefit analysis for ERTS experiments, volumes 1 and 2

The basic elements of a cost-benefit study are discussed along with special considerations for ERTS experiments. Elements required for a complete economic analysis of ERTS are considered to be: statement of objectives, specification of assumptions, enumeration of system alternatives, benefit analysis, cost analysis nonefficiency considerations, and final system selection. A hypothetical cost-benefit example is presented with the assumed objective of an increase in remote sensing surveys of grazing lands to better utilize available forage to lower meat prices.

Source record↗

NASA NTRS1975

Radiative property investigation

Measurements of the bidirectional reflections of NASA paints Z-93 and S-13G were made for 0.5, 1.78, and 2.5 microns, source incidence angles of 0, 30, 60, and 75 deg, and four detector azimuth positions. The bidirectional reflectance distribution was found to be near Lambert for azimuth positions not to close to 180 deg from the source incident azimuth. The reflectance distribution at an azimuth of 180 deg from the source is close to Lambert for near normal source incidents angles, and becomes much larger than Lambert as the source incident angle approach grazing. The reflectance deviates from Lambert as the wavelength increases. Comparison of data for the paints shows Z-93 reflectance is much closer to Lambert than S-13G. When there is a peak in the reflectance distribution it occurred at the specular angle or an angle larger than the specular angle.

Scott, R. L., Jr.↗

NASA NTRS1974

The X-ray spectrographic telescope

The S-054 X-ray telescope, which operated successfully throughout the eight-month Skylab mission, is a grazing incidence instrument with a spatial resolution of the order of 2 arc sec on axis. The total wavelength range observed by the instrument is 2 to 60 A. Crude spectral resolution within this range is achieved by means of a series of six X-ray filter materials. A spectrographic mode of operation, employing an objective grating, is used to obtain spectra of flare events and selected coronal features.

Vaiana, G. S.↗

NASA NTRS1975

Scanning Kirkpatrick-Baez X-ray telescope to maximize effective area and eliminate spurious images - Design

We consider the design of a Kirkpatrick-Baez grazing-incidence X-ray telescope to be used in a scan of the sky and analyze the distribution of both properly reflected rays and spurious images over the field of view. To obtain maximum effective area over the field of view, it is necessary to increase the spacing between plates for a scanning telescope as compared to a pointing telescope. Spurious images are necessarily present in this type of lens, but they can be eliminated from the field of view by adding properly located baffles or collimators. Results of a computer design are presented.

Kast, J. W.↗

NASA NTRS1975

Large area extreme ultraviolet focusing collector

A grazing incidence one-dimensional focusing collector for use in the extreme ultraviolet is described. The collector has a field of view of 1 x 50 deg, a focal length of 3015 cm, and a total unobstructed area of 224 sq cm. The instrument employs an interchangeable detector package of either channel-electron multipliers or proportional counters which yield a limiting sensitivity of 1.0 photons/sq cm sec A at 170 A and 0.05 photons/sq cm sec A at 90 A, respectively, for one second integrations. The design and calibration of the instrument are described in detail. Data obtained by this instrument during recent rocket flights are presented.

Henry, P.↗

NASA NTRS1975

One-dimensional focusing X-ray telescope for stellar X-ray astronomy

A one-dimensional X-ray telescope of the Kirkpatrick-Baez design is described. The instrument consists of a grazing-incidence X-ray telescope and a multiwire proportional counter. The optics were provided with a gold reflecting surface to yield an energy response from below 0.25 to above 4.0 keV. The angular resolution of the system is 6 min by 9.5 deg over a 1.1 deg by 9.5 deg field of view.

Helava, H.↗

NASA NTRS1974

The ERTS-1 investigation (ER-600). Volume 4: ERTS-1 range analysis

The Range Analysis Team conducted an investigation to determine the utility of using LANDSAT 1 data for mapping vegetation-type information on range and related grazing lands. Two study areas within the Houston Area Test Site (HATS) were mapped to the highest classification level possible using manual image interpretation and computer aided classification techniques. Rangeland was distinguished from nonrangeland (water, urban area, and cropland) and was further classified as woodland versus nonwoodland. Finer classification of coastal features was attempted with some success in differentiating the lowland zone from the drier upland zone. Computer aided temporal analysis techniques enhanced discrimination among nearly all the vegetation types found in this investigation.

Erb, R. B.↗

NASA NTRS1976

Extreme ultraviolet survey experiment MA-083

A grazing incidence telescope sensitive to radiation in the 5- to 100-nanometer band was flown in the Apollo service module. On 10 nighttime revolutions, the command and service module was maneuvered to point the instrument at 30 different stellar targets for periods of 1 to 20 minutes, thus constituting the first sensitive search for extreme ultraviolet radiation from nonsolar sources. Several hours of supplementary data were also obtained during nighttime orbits when other experiments in the scientific instrument module bay were operating. Preliminary analysis of a small fraction of the total data indicates the definite detection of a strong source of extreme ultraviolet radiation during observations made during revolution 109. The source is located in Coma Berencies. The suggested optical identification is the white dwarf HZ 43. If this association is correct, the star has the highest temperature of any known white dwarf. Regardless of the optical identification, however, this object is the first nonsolar source to be detected in the extreme ultraviolet band.

Bowyer, S.↗

NASA NTRS1976

Prediction of the acoustic impedance of duct liners

Recent research which contributes to the prediction of the acoustic impedance of duct liners is reviewed. This review includes the linear and nonlinear properties of sheet and bulk type materials and methods for the measurement of these properties. It also includes the effect of grazing flow on the acoustic properties of materials. Methods for predicting the properties of single or multilayered, point reacting or extended reaction, and flat or curved liners are discussed. Based on this review, methods for predicting the properties of the duct liners which are typically used in aircraft engines are recommended. Some areas of needed research are discussed briefly.

Zorumski, W. E.↗

NASA NTRS1976

Discovery of a nonsolar extreme-ultraviolet source

Results are reported for observations of EUV emission from an extrasolar object which were made with a grazing-incidence telescope during the Apollo-Soyuz mission. The total energy flux in the spectral band between 170 and 620 A is estimated to be approximately 4 by 10 to the -9th power erg/sq cm per sec. It is shown that the data support the identification of the EUV object with the ultrasoft X-ray source in Coma Berenices. The source of both emissions is suggested to be the hot white dwarf HZ 43, located at right ascension 13 hr 43 min and declination +29 deg 22 min (1950). The temperature of HZ 43 is estimated as 110,000 K, giving it the highest temperature of any known white dwarf.

Lampton, M.↗

NASA NTRS1976

High-resolution imaging X-ray detector

The paper describes an X-ray detector using microchannel plates as a photocathode surface and imaging photoelectron multiplier, and a crossed wire grid as a two-dimensional position-sensitive detector. The position resolution is 10 microns. The crossed wire grid consists of 100-micron-diam wires on 200-micron centers. Position sensing is accomplished by electronic interpolation to 1/20 of the wire spacing. The quantum efficiency of the microchannel plates varies from 29% at 0.28 keV to 5% at 3 keV. This detector will provide second-of-arc X-ray imaging in the focal plane of the 342.9-cm focal length grazing-incidence telescope being prepared for the HEAO-B observatory. By addition of suitable photocathodes, it can be used for single-photon imaging light detection in the UV, visible, and near-IR-ranges. In all cases, it gives a very low dark counting rate, allows timing of individual events to 1 microsec or less, and can handle counting rates up to 10,000 per sec.

Kellogg, E.↗

NASA NTRS1975

Spatial structure and temporal development of a solar X-ray flare observed from Skylab on June 15, 1973

Morphological and quantitative analyses are presented of a 1B solar flare that was observed with high spatial and temporal resolution by the S-054 grazing-incidence X-ray telescope aboard Skylab. It is found that the flare had the configuration of a compact region with a characteristic size of the order of 30 arcsec at the intensity peak, the interior of the region appeared to be highly structured and to consist of temporally changing complex loop systems, brightening over an extended part of the active region preceded the flare onset, and the impulsive phase was marked by rapid brightening in the loop structures. The X-ray photographs also indicate that the X-ray emission was centered over the neutral line of the longitudinal magnetic field, loop systems formed at successively increasing heights during the decay phase, and different regions of the flare had distinctly different light curves. The flux profiles for the different regions are shown to suggest continued heating during the decay phase. It is concluded that flare models should be based on a multiplicity of volumes ordered in loops of successively larger scale lengths and heights rather than on a single point of energy release and deposition.

Pallavicini, R.↗