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Results for “X-ray image analysis”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 55 records · Page 3
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NASA NTRS1976

A correlation study based on Al/Si X-ray fluorescence data from southwestern part of Mare Serenitatis

A correlation study based on Al/Si intensity ratios, broad-spectrum visible-albedo measurements, color-difference photography, color-ratio images, and spectral-reflectivity curves was undertaken to understand why the Tacquet Formation in southwestern Mare Serenitatis has unusually low visible albedos for the Al/Si intensity ratios measured by the Apollo 15 X-ray fluorescence experiment. The statistical analysis of the Al/Si data is described, general correlations among all the remote-sensing data are noted, and correlations in the area of the Tacquet Formation are examined. It is shown that the discrepancy between visible albedos and Al/Si intensities may be due primarily to the presence of unevenly deposited highland-type ejecta from Menaleus crater, although the possibility cannot be excluded that the Tacquet Formation is more complex than a simple mixture of highland and mare materials.

Andre, C. G.↗
NASA NTRS1979

HEAO Science Symposium

Scientific results from the early analysis of data from the HEAO 1 mission are presented. Development of astronomical catalogs and maps, X-ray variability, extragalactic astronomy, X-ray iron line emission, and optical identification and spectroscopy of X-ray sources are among the topics discussed. Results from HEAO 2 imaging and nonimaging instruments are included.

Dailey, C.↗
NASA NTRS1980

Remote sensing data applied to the evaluation of soil erosion caused by land-use. Ribeirao Anhumas Basin Area: A case study

Formerly covered by a tropical forest, the study area was deforested in the early 40's for coffee plantation and cattle raising, which caused intense gully erosion problems. To develop a method to analyze the relationship between land use and soil erosion, visual interpretations of aerial photographs (scale 1:25.000), MSS-LANDSAT imagery (scale 1:250,000), as well as automatic interpretation of computer compatible tapes by IMAGE-100 system were carried out. From visual interpretation the following data were obtained: land use and cover tapes, slope classes, ravine frequency, and a texture sketch map. During field work, soil samples were collected for texture and X-ray analysis. The texture sketch map indicate that the areas with higher slope angles have a higher susceptibilty to the development of gullies. Also, the over carriage of pastureland, together with very friable lithologies (mainly sandstone) occuring in that area, seem to be the main factors influencing the catastrophic extension of ravines in the study site.

Dejesusparada, N.↗
NASA NTRS1981

Multi-spacecraft observations of solar hard X-ray bursts

The role of multi-spacecraft observations in solar flare research is examined from the point of view of solar hard X-ray bursts and their implications with respect to models of the impulsive phase. Multi-spacecraft measurements provide a stereoscopic view of the flare region, and hence represent the only direct method of measuring directivity of X-rays. In absence of hard X-ray imaging instruments with high spatial and temporal resolution, multi-spacecraft measurements provide the only means of determining the radial (vertical) structure of the hard X-ray source. This potential of the multi-spacecraft observations is illustrated with an analysis of the presently available observations of solar hard X-ray bursts made simultaneously by two or more of the following spacecraft: International Sun Earth Explorer-3, Pioneer Venus Orbiter, Helios-B and High Energy Astrophysical Observatory-A.

Kane, S. R.↗
NASA NTRS1976

Evidence for opposed currents in active region loops

EUV and X-ray images of the sun are used as tracers of the magnetic-field structure in the solar atmosphere in order to study the existence of currents in active regions. Criteria are suggested for comparing the data with theoretical extrapolations of magnetic-field lines above the level of magnetograph observations. Analysis of the data presented in conjunction with force-free field calculations suggests the existence of currents flowing in opposite directions in nearby sets of loops in the active regions considered. Some simple qualitative implications of opposed current structures are suggested.

Levine, R. H.↗
NASA NTRS1975

The interpretation of simultaneous soft X-ray spectroscopic and imaging observations of an active region

Simultaneous soft X-ray spectroscopic and broad-band imaging observations of an active region have been analyzed together to determine the parameters which describe the coronal plasma. From the spectroscopic data, models of temperature-emission measure-elemental abundance have been constructed which provide acceptable statistical fits. By folding these possible models through the imaging analysis, models which are not self-consistent can be rejected. In this way, only the oxygen, neon, and iron abundances of Pottasch (1967), combined with either an isothermal or exponential temperature-emission-measure model, are consistent with both sets of data. Contour maps of electron temperature and density for the active region have been constructed from the imaging data. The implications of the analysis for the determination of coronal abundances and for future satellite experiments are discussed.

Davis, J. M.↗
NASA NTRS1972

A computer program to evaluate optical systems

A computer program is used to evaluate a 25.4 cm X-ray telescope at a field angle of 20 minutes of arc by geometrical analysis. The object is regarded as a point source of electromagnetic radiation, and the optical surfaces are treated as boundary conditions in the solution of the electromagnetic wave propagation equation. The electric field distribution is then determined in the region of the image and the intensity distribution inferred. A comparison of wave analysis results and photographs taken through the telescope shows excellent agreement.

Innes, D.↗
NASA NTRS1980

X-ray evidence of coronal preflare emission

Soft X-ray images from the Skylab AS&E telescopes are used to determine whether systematic preflare X-ray brightenings exist either at the flare site or in adjacent parts of the active region, the characteristics of such brightenings, and their implications for the theory of preflare coronal conditions. A statistical study is given of preflare X-ray events, along with an analysis of the best observed events, including comparisons with high time resolution H-alpha data. It is concluded that a majority of the flares studied may have X-ray preflare features, which were typically not at the flare site, but rather adjacent to the active region neutral line. A single feature was evident in most of the preflare events.

Webb, D. F.↗
NASA NTRS1981

Wedge-and-strip anodes for centroid-finding position-sensitive photon and particle detectors

The paper examines geometries employing position-dependent charge partitioning to obtain a two-dimensional position signal from each detected photon or particle. Requiring three or four anode electrodes and signal paths, images have little distortion and resolution is not limited by thermal noise. An analysis of the geometrical image nonlinearity between event centroid location and the charge partition ratios is presented. In addition, fabrication and testing of two wedge-and-strip anode systems are discussed. Images obtained with EUV radiation and microchannel plates verify the predicted performance, with further resolution improvements achieved by adopting low noise signal circuitry. Also discussed are the designs of practical X-ray, EUV, and charged particle image systems.

Martin, C.↗
NASA NTRS1975

Vidicon spectral imaging - Color enhancement and digital maps

A silicon imaging photometer system (SIPS) was used to obtain visible and near-infrared spectral imaging data in four narrow bandpasses (0.38, 0.56, 0.85, and 1.05 microns) for a 400-by-400-km lunar region which includes the Serenitatis-Tranquillitatis border. Three ratio frames were used to make color composites of radio images, and spectral maps based on interactive 'cluster' analysis were produced from four video channels. A low albedo titanium-poor unit occurs near the southern edge of the Serenitatis and south of the basin; this unit appears to postdate the high-titanium dark Tranquillitatis and 'blue-ring' material and may be associated with an Al/Si anomaly noticed in Apollo orbital X-ray data.

Johnson, T. V.↗
NASA NTRS1975

EUV emission, filament activation and magnetic fields in a slow-rise flare

Results are reported for observations and analysis of synoptic data on a 1B flare that occurred on January 19, 1972. The observations include large-scale H-alpha movies of the flare and pre-flare developments, OSO-7 satellite data on soft X-ray and EUV developments, magnetograms, and hard X-ray observations. Theoretical force-free magnetic field configurations are compared with structures seen in the soft X-ray, EUV, and H-alpha images, and the evolution of the flare is described. The energy available for the flare is estimated from the change of magnetic field inferred from the H-alpha filtergrams and from force-free field calculations. It is suggested that the flare originated in a twisted filament where it was compressed by emerging fields, and it is shown that the flare started below the corona and appeared to derive its energy from the magnetic fields in or near the filament.

Rust, D. M.↗
NASA NTRS1981

Solar Maximum Mission experiment - Early results from the soft X-ray polychromator experiment

It is pointed out that the X-ray polychromator experiment has been in operation on the Solar Maximum Mission satellite for more than three months. Using a number of different modes, the polychromator is observing flares and active regions in the wavelength range 1-23 A. These modes include polychromatic imaging, high resolution line profiles, high dispersion spectra, and light curves with high time-resolution. Data are described and some of the early analysis and interpretation is presented. All the interpretations are based on simple approximate methods; it is noted, however, that in most cases more elaborate and reliable methods are close to being applied.

Gabriel, A. H.↗
NASA NTRS1981

X-ray emission from Of stars and OB supergiants

The result of a survey of X-ray emission from luminous early-type stars is reported in which observations were made using the imaging proportional counter on the Einstein Observatory. The survey suggests that all Of stars and OB supergiants earlier than B1 I are X-ray sources with luminosities not less than 10 to the 32nd ergs/s and that some later B supergiants have X-ray luminosities not less than 10 to the 31st ergs/s. The X-ray luminosities are roughly 10 to the -7.2nd of the bolometric luminosities for supergiants earlier than B1 and perhaps a factor of 3 less for later B supergiants. Spectral analysis of the X-rays in conjunction with information on anomalous ionization in the wind from four of the strongest sources implies that the data are not consistent with a model in which the X-rays originate in a thin slab coronal zone at the base of the wind. Constraints on the source of X-rays from B supergiants are derived by combining the X-ray flux information with that on ultraviolet line anomalies.

Cassinelli, J. P.↗
NASA NTRS1979

Analysis of NOAA-MSFC GOES X-ray telescope

The general telescope system was assumed to be a paraboloid-hyperboloid in a Wolter Type 1 configuration. The equations which specify the telescope parameters and the resolution as a function of the collecting area are discussed as well as the spot size and point response function for off-axis rays. The measured resolution of the Goddard ATM X-ray telescope (S-056) is compared to the rms blur circle radius and the full width half maximum of the line spread function. An empirical scaling formula, Eq. 26, which transforms the rms blur circle radius into a more accurate measure of resolution, is introduced. The geometrical imaging properties of the proposed NOAA-MSFC GOES X-ray telescope are considered. Conclusions and alternate mirror designs are included.

Shealy, D. L.↗
NASA NTRS1978

Iodine imaging using spectral analysis

Existing radiographic imaging systems provide images which represent an integration or averaging over the energy spectrum. In order to provide noninvasive angiography it is necessary to image the relatively small amounts of iodine which are available following an intravenous administration. This is accomplished by making use of the special spectral characteristics of iodine. Two methods will be presented. One involves a special grating for encoding the iodine information in the form of a fine line pattern. This is subsequently decoded to provide images of iodinated structures which are otherwise almost invisible. The second method utilizes a scanned X-ray beam which is rapidly switched in the high energy region. In this region, iodine experiences significant variations in the attenuation coefficient while bone and soft tissue do not. An efficient and accurate X-ray detector can be used with scanned X-ray beams. This provides a high degree of sensitivity enabling the visualization of small vessels containing relatively dilute iodine.

Macovski, A.↗
NASA NTRS1977

Spectrophotometry of the transient X-ray source A0620-00

Optical observations of the transient X-ray source A0620-00 over the wavelength range from about 3200 to 6600 A are analyzed which were made with the 5-m Hale telescope using a multichannel spectrometer, a digital spectrograph with a cooled integrating SIT vidicon, and an image photon-counting system attached to the camera of the coude spectrograph. Infrared observations at 1.65, 2.2, and 3.5 microns are also examined. Individual spectral lines of special interest are discussed, the E(B-V) color excess is estimated to be about 0.40, and a distance of 1200 pc is adopted. Analysis of the continuous spectrum yields several simple binary models. A specific model is proposed in which one of the continuum sources is an optically thick object characterized by a model atmosphere at a temperature of 25,000 to 30,000 K and the second source is either a cool black body at 4000 K or a partially optically thick source of bound-free plus free-free radiation from a hydrogen gas with an electron temperature of at least 100,000 K. Some possible parameters of these sources and of the accretion disk are considered.

Oke, J. B.↗
NASA NTRS1976

Evidence for magnetic energy storage in coronal active regions

Examination of X-ray images obtained by the S-054 X-ray spectrographic telescope on Skylab shows the presence of some atypical X-ray-emitting coronal structures in active regions which are not consistent with potential extrapolations of photospheric magnetic fields. Analysis of the observed temporal changes in the X-ray-emitting active-region structures demonstrates that the majority of these consist of brightness changes representing temperature (and perhaps density) variations of the material in the loops.

Krieger, A. S.↗