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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 145 records · Page 8
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NASA NTRS1979

The hydrogen lines in the high-luminosity quasar B2 1225+31

The emission lines H-alpha, H-beta + forbidden O III, and L-alpha have been observed in the high-redshift quasar 1225+31. The ratios of line intensities in 1225+31 are found to be approximately 0.8 for L-alpha/H-alpha, about 4 for H-alpha/(H-beta + forbidden O III), and between 4 and 10 for H-alpha/H-beta. The observed value of L-alpha/H-alpha agrees well with the ratio derived by Baldwin (1977) on the basis of a composite quasar spectrum, as well as with direct determination of this ratio in 3C 273 and PKS 0237-23. The ratio H-alpha/H-beta is in the range of values found for a sample of low-redshift quasars by Baldwin (1975). The low value for the L-alpha/H-alpha ratio cannot be reasonably explained by foreground extinction between the sun and 1225+31.

Soifer, B. T.↗
NASA NTRS1979

Voyager observations of the interstellar medium in the 500- to 1700-A spectral region

Observations of the interstellar medium have been obtained in the 500-1700-A spectral region by the ultraviolet spectrometers installed on the Voyager spacecraft. A preliminary analysis of the least complex of the spectra obtained to date indicates measurable emission in spectral lines at 584, 1026, and 1216 A. These emissions are identified with resonance scattering of solar radiation in transitions of helium and atomic hydrogen. The observations in the direction alpha 324 deg, delta-23 deg contain no measurable direct emission or scattering of stellar radiation by the interstellar medium to an upper limit of 0.0005 R/A at 975 A. Spectra obtained in other directions indicate measurable sources of apparent continua having relatively broad spatial extent.

Shemansky, D. E.↗
NASA NTRS1979

Pre-Voyager velocities, accelerations and shrinkage rates of Jovian cloud features

Voyager I data provide detailed information on the latitudinal dependence of velocities in the Jovian atmosphere. In the present paper, pre-Voyager velocity data are summarized, and gross differences with the Voyager I results are revealed. Analytical expressions are derived for the shrinkage rates and acceleration of the Great Red Spot and white ovals (located at -23 degrees and -34 degrees latitude, respectively) for the period from 1943 to 1979.

Beebe, R. F.↗
NASA NTRS1979

Intensities and N2 collision-broadening coefficients measured for selected H2O absorption lines between 715 and 732 nm

Intensities and N2 collision-broadening coefficients are measured for 62 water vapor absorption lines between 715 and 732 nm potentially applicable to laser remote sensing of atmospheric water vapor. Absolute line strengths and widths were determined from spectra corrected for instrument resolution, air-path absorption and Lorentz and Doppler broadening for pure water vapor and water vapor-nitrogen mixtures in a multipass absorption cell with a base path length of 25 m (White cell). Line strengths are observed to range from 4 x 10 to the -25th to 4 x 10 to the -23rd kayser/molecule per sq cm, and collision broadening coefficients are found to be approximately equal to 0.1 kayser/atm.

Wilkerson, T. D.↗
NASA NTRS1979

Analysis of X-ray and EUV spectra of solar active regions

Data acquired by two flights of an array of six Bragg crystal spectrometers on an Aerobee rocket to obtain high spatial and spectral resolution observations of various coronal features at soft X-ray wavelengths (9-23A) were analyzed. The various aspects of the analysis of the X-ray data are described. These observations were coordinated with observations from the experiments on the Apollo Telescope Mount and the various data sets were related to one another. The Appendices contain the published results, abstracts of papers, computer code descriptions and preprints of papers, all produced as a result of this research project.

Strong, K. T.↗
NASA NTRS1979

Proceedings of the 13th Project integration meeting

Progress made by the Low Cost Solar Array Project during the period April through August 1979 is presented. Reports are given on project analysis and integration; technology development in silicon material, large area sheet silicon, and encapsulation; production process and equipment development; engineering and operations, and a discussion of the steps taken to integrate these efforts. A report on, and copies of viewgraphs presented at the Project Integration Meeting held August 22-23, 1979 are presented.

Mcdonald, R. R.↗
NASA NTRS1980

Spectrophotometric observations of P/Schwassmann-Wachmann 1 during outburst

Spectra of Comet Schwassmann-Wachmann 1 were obtained on November 26-27, 1978 and February 15, 1979 using the Cassegrain Digicon spectrograph, and on February 21-23, 1979 using the IDS spectrograph of McDonald Observatory. All spectra were obtained while the comet was in an extended series of outburst (12th-13th mag). The spectra were predominantly reflected solar light, indicating the outburst was very rich in dust. Weak emission between 4000 and 4050 A, and between 4240 and 4290 A was detected in November 1978 and is probably due to CO(+). These outbursts, and the detection of CO(+), indicate that comets are not inactive at distances as great as 6 AU.

Cochran, A. L.↗
NASA NTRS1980

A high-sensitivity search for extraterrestrial intelligence at lambda 18 cm

A targeted high-sensitivity search for narrow-band signals near a wavelength of 18 cm has been conducted using the 91-m radiotelescope of the National Radio Astronomy Observatory. The search included 201 nearby solar-type stars and achieved a frequency resolution of 5.5 Hz over a 1.4-MHz bandwidth. This high spectral resolution was obtained through a non-real-time reduction procedure using a Mark I VLBI recording terminal in conjunction with the CDC 7600 computational facility at the NASA-Ames Research Center. This is the first high-resolution search for narrow-band signals in this wavelength regime. To date it is the most sensitive search per unit observing time of any search strategy which does not postulate a unique magic frequency. Data show no evidence for narrow-band signals due to extraterrestrial intelligence at a 12-standard-deviation upper limit on signal strength of 1.1 x 10 to the -23rd W/sq m.

Tarter, J.↗
NASA NTRS1980

Determination of the total grain size distribution in a vulcanian eruption column, and its implications to stratospheric aerosol perturbation

The total grain distribution of tephra from the eruption by the Fuego volcano in Guatemala on Oct. 14, 1974 was determined by grain size analysis. The region within each isopach has a grain distribution which was weighted proportionally to its percentage volume; the total distribution had a median grain size of 0.6 mm and a sorting coefficient of 2.3. The ash composed of fine particles did not fall in the volcano area as part of the recognizable tephra blanket; the eruption column reached well into the stratosphere to the height of 10-12 km above sea level, with mass flux rate estimated altitudes of 18-23 km

Murrow, P. J.↗
NASA NTRS1980

A bimodal search strategy for SETI

A SETI plan has been developed jointly by the NASA Ames Research Center and the Jet Propulsion Laboratory with the objective of both observing all potential sites to some limiting equivalent isotropic radiated power and surveying with greater sensitivity a set of especially promising sites. The bimodal search strategy assumes that existing radio telescopes with state-of-the-art receivers and data processing devices will have the sensitivity to explore the vicinity of nearby stars for similar transmitters and the entire galaxy for more powerful signals. The discrete source observational mode is designed to observe 773 F, G and K-type stars within 25 pc of the sun at frequencies from 1.2 to 3 GHz and spot bands between 3 and 25 GHz with sensitivities from 10 to the -25th to 10 to the -27th W/sq m. The sky survey is intended to search the entire celestial sphere between 1.2 and 10 GHz and spot bands between 10 and 25 GHz at a sensitivity limit of approximately 10 to the -23rd times the square root of the frequency. Instrumentation for the surveys includes a large multichannel spectrum analyzer. Immediate goals of the program are the investigation of the RF background at high resolution and the development of signal detection algorithms, with operation to begin in 1984.

Gulkis, S.↗
NASA NTRS1981

The Ophiuchus cluster - A bright X-ray cluster of galaxies at low galactic latitude

The discovery of an extended X-ray source identified with a cluster of galaxies at low galactic latitude is reported. The source, designated the Ophiuchus cluster, was detected near 4U 1708-23 with the HEAO 1 Scanning Modulation Collimator, and identified with the cluster on the basis of extended X-ray size and positional coincidence on the ESO/SRC (J) plate of the region. An X-ray flux density in the region 2-10 keV of approximately 25 microJ was measured, along with an X-ray luminosity of 1.6 x 10 to the 45th ergs/sec and an X-ray core radius of approximately 4 arcmin (0.2 Mpc) for an assumed isothermal sphere surface brightness distribution. The X-ray spectrum in the range 2-10 keV obtained with the HEAO 1 A-2 instrument is well fit by a thermal bremsstrahlung model with kT = 8 keV and a 6.7-keV iron line of equivalent width 450 eV. The steep-spectrum radio source MSH 17-203 also appears to be associated with the cluster, which is the closest and brightest representative of the class of X-ray clusters with a dominant central galaxy.

Johnston, M. D.↗
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

Topography of Martian central volcanoes

Results are presented of the topographic mapping of six large central volcanoes on Mars. Stereo images of the volcanoes Olympus Mons, Elysium Mons, Albor Tholus, Ceraunius Tholus, Uranius Tholus and Uranius Patera were acquired by Viking Orbiter 1, and pairs of images were compiled into topographic maps through the use of digital image measurement techniques. Olympus Mons is found to have the general form of a terrestrial basaltic shield constructed almost entirely from lava flows, however with an altitude of 20-23 km and flank slopes averaging about 4 deg; a high nominal density indicates that anomalously dense lithosphere underlies the shield. Uranius Patera is observed to be a similar feature of present relief about 2 km, with its lower flanks buried by later lava flood deposits. Elysium Mons has about 13 km of local relief with average slopes of 4.4 deg, although its upper flank slopes are significantly steeper than those of Olympus Mons, suggesting a shield volcano modified by a terminal phase of mixed volcanic activity. Albor Tholus is found to be a partially buried 3-km shield-like construct, while Ceranius and Uranius Tholus are steeper cone-like features with reliefs of about 6 and 2 km, respectively, which may be lava shield constructs modified by a terminal stage of explosive activity.

Blasius, K. B.↗
NASA NTRS1982

Performance of PTFE-lined composite journal bearings

Plain cylindrical journal bearings consisting of aramid fiber reinforced epoxy outer shells and glass fiber reinforced PTFE lubricating liners were evaluated. All materials in these bearings are electrically nonconductive; thus eliminating the problem of galvanic corrosion sometimes encountered with metal bearings installed in dissimilar metal mountings. Friction and wear characteristics were determined for loads, temperatures, and oscillating conditions that are typical of current airframe bearing applications. Friction and wear characteristics were found to be compatible with most airframe bearing requirements from -23 C to 121 C. Contamination with MIL H-5606 hydraulic fluid increased wear of the PTFE liners at 121 C, but did not affect the structural integrity of the aramid/epoxy composite.

Sliney, H. E.↗
NASA NTRS1982

The absence of rapid X-ray variability in active galaxies

Variations on time scales ranging from minutes to several hours in the X-ray flux from 54 observations of 38 active galaxies are identified. The sample is composed mostly of Seyfert I galaxies but also includes radio galaxies, NELG's BL Lacs and 3C 273. Only NGC 6814 varied on time scales as short as 100 sec. No other source was observed to vary with a time scale of less than 12 hours. Large amplitude short term variations are not a characteristic of the X-ray emission from active galaxies. Upper limits on sigma sub I/I ranged from 2% for Cen A, 5% for NGC 4151, to approximately 20% for sources giving 1 ct/sec in the detector. Three objects NGC 3227, NGC 4151 and MCG 5-23-16 show variability consistent with a time scale of approximately 1 day. Ways to reconcile the rapid variability seen for NGC 6814 (and NGC 4051) with the general stability observed for the other objects are considered.

Tennant, A. F.↗
NASA NTRS1982

Evidence for quasi-stationary reconnection at the dayside magnetopause

The paper investigates several highly unusual encounters with the earth's magnetopause, that occurred during an approximately 5-hour period on November 22-23, 1979, when the ISEE 1 and 2 were near orbit apogee. A large decrease in the dynamic pressure exerted by the solar wind resulted in an expansion of the magnetosphere to and beyond the apogee of the ISEE 1 and 2 orbit, and the subsolar magnetopause of about 20.4 earth radii is farther than normal in geocentric distance by a factor of about 2. Field rotations varying from about 80 to 120 deg were involved in the transition from the magnetosheath to the magnetosphere, and hodograms of the tangential component of the magnetic field vector suggest that the magnetopause was a rotational discontinuity. These observations indicate that on occasion reconnection at the dayside magnetopause can be a quasi-stationary process.

Gosling, J. T.↗
NASA NTRS1982

The X-ray spectrum and time variability of narrow emission line galaxies

X-ray spectral and temporal observations are reported for six narrow emission line galaxies (NELGs), all of which are fitted by power-law X-ray spectra of energy slope 0.8 and have column densities in the line of sight greater than 1 x 10 to the 22nd atoms/sq cm. Three of the objects, NGC 526a, NGC 2110 and MCG-5-23-16 are variable in their X-ray flux, and the latter two, along with NGC 5506 and NGC 7582, showed detectable variability in at least one observation. The measured X-ray properties of these NELGs, which also included NGC 2992, strongly resemble those of previously-measured type 1 Seyferts of the same X-ray luminosity and lead to the conclusion of great similarity between the NELGs and low-luminosity type 1 Seyferts. The implications of these observations for the optical line-emitting region structure of these galaxies are discussed.

Mushotzky, R. F.↗
NASA NTRS1981

Detection of regional air pollution episodes utilizing satellite data in the visual range

A comparative analysis of satellite-observed haze patterns and ground-based aerosol measurements is carried out for July 20-23, 1978. During this period, a significant regional air pollution episode existed across the northeastern United States, accompanied by widespread haze, reduced surface visibility, and elevated sulfate levels measured by the Sulfate Regional Experiment (SURE) network. The results show that the satellite-observed haze patterns correlate closely with the area of reported low surface visibility (less than 4 mi) and high sulfate levels. Quantitative information on total aerosol loading derived from the satellite-digitized data, using an atmospheric radiative transfer model, agrees well with the results obtained from the ground-based measurements.

Bowley, C. J.↗