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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 397 records · Page 22

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NASA NTRS1975

An upper limit to the low-energy X-ray flux from beta Persei

A region of the sky including the binary system Algol (beta Persei) was observed with a one-dimensional, grazing-incidence X-ray telescope sensitive in the energy range from 0.5 to 4.0 keV. No statistically significant flux was detected above that attributable to the diffuse and cosmic-ray induced backgrounds. This result allows an upper limit of .02 billionths of an erg/sq cm sec keV at 1.6 keV to be set for the X-ray emission from this source at the epoch of observation. The absence of detectable low-energy X-rays is consistent with a thermal radio source, on condition that no flares occurred at the time of observation.

Kifune, T.↗

NASA NTRS1975

An upper limit to the low-energy X-ray flux from Beta Persei

A region of the sky including the binary system Algol (Beta Persei) was observed with a one-dimensional grazing-incidence X-ray telescope sensitive in the energy range from 0.5 to 4.0 keV. No statistically significant flux was detected above that attributable to the diffuse and cosmic-ray induced backgrounds. This result allows an upper limit of 2 by 10 to the -11th power ergs/sq cm/sec/keV at 1.6 keV to be placed on the X-ray emission from this source at the epoch of observations. It is concluded that the absence of detectable low-energy X-rays is consistent with a thermal radio source, provided that no flares occurred at the time of observation.

Kifune, T.↗

NASA NTRS1976

Evidence of outward flow of plasma in a coronal hole

The solar spectrum was photographed in the range 200-700 A with a grazing-incidence stigmatic rocket spectrograph. Doppler shifts of the three coronal lines Si XI (303 A), Mg X (610 A), and Mg IX (368 A) were measured for various regions of the solar disk, including a coronal hole. From the relative shifts in the latter region, an average outward velocity of 16 km/s was computed for the plasma in the coronal hole. The full widths at half-maximum for the above lines were appreciably less in the coronal-hole region than in a quiet region, indicating a lower temperature in the hole. Both the measured velocity and the temperature results are consistent with solar-wind data and with current theories of coronal holes.

Cushman, G. W.↗

NASA NTRS1976

Experimental investigation of Stark broadening and plasma polarization shift of ionized helium resonance lines

Stark broadening and shift measurements were performed on ionized helium resonance lines from a fully ionized helium plasma in a low-inductance electromagnetic T tube. Both time-integrated photographic and time-resolved photoelectric measurements of the lines were performed with a grazing incidence spectrometer. Electron density and temperature were determined from the widths of the He II 4686-A and the He I 5876-A lines and the He II 4686-A line to continuum ratio, respectively. It was found that all ionized helium resonance lines were emitted optically thick by a homogeneous plasma slab and self-reversed by a thin cooler boundary layer. Marked blue shifts of 0.07 plus or minus 0.05 A which may be due to plasma polarization were noted.

Neiger, M.↗

NASA NTRS1976

Wavelengths and levels of the Na I isoelectronic sequence from K IX through Mn XV

The seven spectra K IX through Mn XV have been analyzed and the series limits determined. We present the adopted wavelengths and the derived energy levels and term splittings. The highly ionized atoms were produced in a spark source and recorded mainly on a 3 m grazing incidence spectrograph. Many new lines have been identified and many previously given wavelengths have been revised. All wavelengths have been examined for consistency by least-squares-fitting procedures and other tests. These procedures indicated misidentified lines and incorrect wavelengths which we corrected when possible. A discussion of the errors is given.

Cohen, L.↗

NASA NTRS1976

Instrumentation for solar spectrophotometry at extreme ultraviolet and soft X-ray wavelengths

The solar extreme ultraviolet and soft X-ray (XUV) spectrum at wavelengths between 20 and 300 A contains a wealth of emission lines from ions formed at temperatures from 10 to the 5th K to greater than 2 x 10 to the 7th K. The requirements for high resolution spectrophotometric instrumentation are discussed in the light of data obtained with extreme ultraviolet and X-ray telescopes flown on Skylab. The design of a grazing-incidence spectroheliometer for active region and flare studies over the wavelength range from 40 to 630 A is presented and recently developed high-efficiency detectors and detector-arrays for use at XUV wavelengths are described.

Timothy, J. G.↗

NASA NTRS1977

Dust-contamination monitor

Compact instrument gives instantaneous reading of accumulation of small particles on glass plate. Instrument is sensitive to particles as small as one hundred microns and should be adaptable to monitoring particulate air pollution or dust levels in semiconductor clean rooms. Dual collimated light sources produce highly monochromatic radiation direct at grazing single angle onto glass plate.

Claysmith, C. R.↗

NASA NTRS1976

Stellar occultation measurements of atmospheric ozone and chlorine from OAO3

The Princeton University telescope on the Orbiting Astronomical Observatory 3 was used for occultation measurements of upper-atmospheric species. The target star, Beta Cen, and observing date were selected so that the line of sight grazed earth's limb at local midnight. Observations at 2580, 2825, 2997, 3100, and 3428 A produced ozone absorption data of high statistical accuracy between 48-km and 114-km tangent altitude. Near-exponential density profiles are obtained up to 85 km. Near 100 km, a significant density excess above the extrapolated low-altitude profile is observed. Near-equatorial observations at altitudes up to approximately 75 km agree well with theoretical calculations. Ozone densities measured at 6.5 to 12.5 deg S latitude above approximately 75 km exceed the theoretical calculations and are not understood at the present time. A search for the 1188-A chlorine line in the 1187-A O2 absorption feature was carried out at tangent altitudes of 96-116 km. An upper limit of 3 ppb to the atomic chlorine mixing ratio at 106 km is found. This upper limit exceeds the expected value for atomic chlorine by a factor of approximately 2.5.

Riegler, G. R.↗

NASA NTRS1976

Effects of solar radiation on the orbits of small particles

A modification of the Robertson (1937) equations of particle motion in the presence of solar radiation is developed which allows for partial reflection of sunlight as a result of rapid and varying particle rotations caused by interaction with the solar wind. The coefficients and forces in earlier forms of the equations are compared with those in the present equations, and secular rates of change of particle orbital elements are determined. Orbital dimensions are calculated in terms of time, probable sizes and densities of meteoric and cometary particles are estimated, and times of infall to the sun are computed for a particle moving in an almost circular orbit and a particle moving in an elliptical orbit of high eccentricity. Changes in orbital elements are also determined for particles from a long-period sun-grazing comet. The results show that the time of infall to the sun from a highly eccentric orbit is substantially shorter than from a circular orbit with a radius equal to the mean distance in the eccentric orbit. The possibility is considered that the free orbital kinetic energy of particles drawn into the sun may be the energy source for the solar corona.

Lyttleton, R. A.↗

NASA NTRS1976

Preflare X-ray morphology of active regions observed with the AS & E telescope on Skylab

Images of active regions obtained with the grazing-incidence X-ray telescope aboard Skylab during the 20-min period preceding eight small X-ray flares are used to investigate the X-ray morphology of the preflare state of the active regions for any evidence of flare buildup. Not a single case is found where preflare brightening occurred in and only in the region which subsequently flared. For two events, no changes in the X-ray morphology of the preflare active region were noted up to within 2 min of the flare onset. Thus, no systematic evidence is found for a preflare buildup in any of these eight events.

Kahler, S. W.↗

NASA NTRS1976

Observations from ERTS of overgrazing and cultivation impact on the earth's surface

ERTS-1 imagery was surveyed for cases of anthropogenic impact, similar to that in the Sinai, evidenced by the Sinai/Negev demarcation line. Reflectivities in several such cases were analyzed using ERTS computer compatible tapes. Sharp increases of surface reflectivity show the severe impact of overgrazing found in several places around the world. Agricultural cultivation can also result in pronounced change of reflectivities, as evidenced by the Montana, USA/Canada demarcation line. Such processes have probably been going on since prehistoric times, increasing with the human population and with the population of the grazing herds.

Otterman, J.↗

NASA NTRS1977

The atmosphere of Sirius B. II - Extreme-ultraviolet observations

The letter reports an observation of Sirius in the extreme-ultraviolet (100-1000 A) band, using a grazing-incidence telescope flown aboard the Apollo-Soyuz mission. No positive flux is detected; under the arbitrary assumption of flat incident spectrum, an upper limit to the flux in the 170-620 A band is 5 billion erg/sq cm per sec. A detailed model-atmosphere analysis, when combined with the EUV limits, places severe constraints on models which attribute the previously reported soft X-ray (44-60 A) flux to thermal radiation from deep layers of the atmosphere of the white dwarf Sirius B. EUV radiation should be detectable from Sirius B just below the sensitivity threshold of the current data, or a thermal origin for the X-ray flux is untenable. If the X-ray flux is thermal, the present results provide extremely sensitive constraints on the temperature and helium abundance of Sirius B: the white dwarf has an effective temperature of 32,000 K to 32,500 K and a helium abundance (relative to hydrogen) of 0.0001 to 0.0002.

Shipman, H. L.↗

NASA NTRS1977

The Shuttle era - A challenge to the earth scientist

Satellite observations of large-scale earth features and phenomena, with either instruments or astronauts, are discussed on the basis of earlier experience (mainly Skylab). Off-nadir views and photographs by astronauts have provided valuable supplements to instrument nadir views, providing cross-checks through remote sensing at different angles, different altitudes, and in different seasons. New information on plate tectonics, global cooling/drying trends, global oceanographic data (changing positions of major ocean current patterns, evolution of warm and cold eddies and their relation to sea temperatures and concentrations of marine fauna, location of internal sea waves, interactions between ocean currents and atmosphere, plankton blooms), storm development, snow cover patterns, lake and sea ice growth, sand-dune patterns, desert storms blown out to sea, effects of grazing and swidden agriculture, and other earth features and phenomena are surveyed.

Muehlberger, W. R.↗

NASA NTRS1977

The reality of comet groups and pairs

Although the common genetic origin of the Kreutz family of sun-grazing comets has generally been accepted, there remains uncertainty with regard to genetic identity among other groups of comets whose orbital elements are nearly alike. Porter (1952) has listed a number of such groups, and Opik (1971) has made a statistical study of the orbits of 472 comets with aphelion distances beyond Saturn. Opik lists 97 groups that show similarities among their three angular elements, calculates an overall probability of some 10 to the -39th power that these similarities could have occurred by chance, and thus concludes that 60% or more of such comets fall into genetic groups containing from two to seven members. This paper explores the statistical reality of Opik's groups utilizing the Monte Carlo method of statistics as well as ordinary probability theory. The conclusion is reached that except for a few pairs, the similarity among orbital elements within the groups is no greater than random expectation.

Whipple, F. L.↗

NASA NTRS1977

Mariner 10 ultraviolet spectrometer - Occultation experiment

A description is given of the spectrometer which was included in the scientific payload of the Mariner 10 spacecraft to measure the extinction properties of the Mercurian atmosphere at extreme ultraviolet wavelengths. The solar intensity was monitored continuously by a grazing incidence pinhole spectrometer in 150 A bands centered at 485, 740, 810 and 895 A. This instrument provided the capability of determining atmospheric surface pressures greater than one-billionth of a millibar.

Broadfoot, A. L.↗

NASA NTRS1977

A survey of soft X-ray limb flare images - The relation between their structure in the corona and other physical parameters

The data used in the investigation were obtained by the American Science and Engineering S-054 experiment on board Skylab. The instrument employed was a grazing incidence X-ray telescope which records images of the sun on film. The morphology of limb flares is investigated and the observed spatial structure is related with the other physical parameters of the region (temperature, density, characteristic times, and energy density). It is concluded that two physically distinct classes of flares exist that differ both in their morphology and in the physical properties which characterize the emitting regions.

Pallavicini, R.↗

NASA NTRS1977

Computer-aided analysis of LANDSAT data for surveying Texas coastal zone environments

The author has identified the following significant results. The study areas were Pass Cavallo and Port O'Connor. The following terrestrial and aquatic environments were discriminated: alternating beach ridges, swales, sand dunes, beach birms, deflation surfaces, land-water interface, urban, spoil areas, fresh and salt water marshes, grass and woodland, recently burned or grazed areas, submerged vegetation, and waterways.

Kristof, S. J.↗

NASA NTRS1977

Reindeer range inventory in western Alaska from computer-aided digital classification of LANDSAT data

An inventory of reindeer-range resources was conducted for the USDA Soil Conservation Service of 1.6 million hectares of wildlands in western Alaska using clustering techniques with digital Landsat data. Computer-aided digital analysis produced a provisional map of rangeland types which was used to design the field collection of vegetation and soil types data. This field data facilitated refinement of the inventory map and was used to describe the map units. The informational classes important to range resources were wet, moist and alpine tundra, tidal marsh, brush and open spruce forest. A significant feature of the study was the extraction of acreage figures by administrative boundaries within the study area. In addition to soil and vegetation association map products (at scales of 1:250,000 and 1:63,360) acreage values were tallied from the digital data for each of the four grazing permit areas established by the Bureau of Land Management.

George, T. H.↗