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  • SPACE SCIENCES  (1,758)
  • Chemical Engineering  (983)
  • LUNAR AND PLANETARY EXPLORATION  (704)
  • SPACE VEHICLES  (609)
  • Cell & Developmental Biology  (608)
  • SPACE RADIATION  (592)
  • 1975-1979  (1,534)
  • 1970-1974  (3,335)
  • 1960-1964  (385)
  • 1978  (1,534)
  • 1972  (3,335)
  • 1961  (385)
Collection
Keywords
Publisher
Years
  • 1975-1979  (1,534)
  • 1970-1974  (3,335)
  • 1960-1964  (385)
Year
  • 1
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    A fast DFT algorithm using complex integer transforms (1978)
    In:  CASI
    Details
    Publication Date: 2006-01-16
    Description: Winograd's algorithm for computing the discrete Fourier transform is extended considerably for certain large transform lengths. This is accomplished by performing the cyclic convolution, required by Winograd's method, by a fast transform over certain complex integer fields. This algorithm requires fewer multiplications than either the standard fast Fourier transform or Winograd's more conventional algorithms.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: The Deep Space Network; p 134-140
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  • 2
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    Interpretation of observed cosmic microwave background radiation (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The Alfven and Mendis (1977) conclusion that dust grains in galaxies render the universe opaque to cosmic microwave background at a red shift ratio equal to 40 is challenged by a calculation of the opacity of galactic dust grains to the microwave background radiation from the time of decoupling at emission red shift ratio equal to 1500 to the present in the standard big bang model. In the present calculation, evolutionary effects on grain opacity and abundance are estimated. At wavelengths used in studying the microwave background, the optical depth of the grains is found to be 0.18 when the deceleration parameter equals 0.03, and 0.05 when the deceleration parameter equals 0.5. The results indicate that microwave background can provide information on an early dense phase of the universe.
    Keywords: SPACE RADIATION
    Type: Nature; 271; Feb. 2
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  • 3
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    Possible correlation of Io's posteclipse brightening with major solar flares (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: In 6 of the 7 instances where posteclipse brightening of Io has been reported by observers using blue filters, a major solar flare occurred within 10 degrees of the sub-Jovian longitude in the 100-day interval prior to observation. In none of the 18 instances where no posteclipse brightening was observed did such a flare occur. It is proposed that a phenomenon associated with a major solar flare causes an increase in the trapped particle flux at Io's orbit by an order of magnitude. The posteclipse brightening may be caused by thermoluminescence of Io's surface material upon emergence. Alternatively, it is possible that the increase in trapped particle flux would warm the surface, creating a temporary atmosphere which would precipitate during eclipse cooling and vaporize in the period of warming after reemergence.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 33; Jan. 197
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  • 4
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    On the ortho-para equilibrium of H2 in the atmospheres of the Jovian planets (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The ratio for the equivalent widths for the unsaturated H2 quadrupole transitions observed in the Jovian planets is calculated and compared with a large number of observations. The comparison indicates that equilibrium hydrogen may be present in Jupiter and Saturn, while Uranus and Neptune exhibit ratios not in accord with equilibrium hydrogen. Observations which can differentiate among the possible states of H2 are proposed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 33; Jan. 197
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  • 5
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    Infrared /JHK/ photometry of meteorites and asteroids (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The paper reports JHK colors observed for ten asteroids and synthesized JHK colors for seven meteorite groups, samples of iron and nickel metal, pyroxene, olivine, feldspar, a lunar anorthite and some terrestrial mineral samples. Pronounced differences are apparent between the chondritic and achondritic meteorite classes; the chondritic classes show less subdued trends in J-H color which reflect their metamorphic grade. We find small but significant differences between the JHK colors of the predominant C and S classes of asteroids. All JHK colors of asteroids observed here fall within the limited domain defined by the various chondritic and iron-rich meteorites but are strikingly different from those of most achondritic meteorites.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics; 13; Mar. 31
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  • 6
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    Background of a shielded Ge(Li) spectrometer at balloon altitudes (1978)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: The background data obtained from an actively shielded Ge(Li) spectrometer flown on a balloon were analyzed and a preliminary model was developed to explain background features including the intensity and time profile of line emission. These features can be explained by a combination of secondary radiation originating in the CsI shield and atmospheric secondary radiation leaking through it.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 462-472
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  • 7
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    Gamma-ray line emission above 8 MeV (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The spectra of energetic nuclei within astrophysical sources may be determined by studying gamma-ray line emissions above 8 MeV. Excited states which can be produced by inelastic scattering, charge exchange, and spallation reactions in the abundant nuclear species were considered in order to identify nuclear lines which may contribute to the gamma spectrum. The cross sections for production of most high-energy states are sparsely measured. Those which were determined are comparable to the cross section for production of the 15.11 MeV level in C-12 with few exceptions. The branching ratios for gamma-ray and particle emission are, however, better known. Of those states considered, 44 measured branching ratios greater than 40% for emission of a gamma-ray with energy above 8 MeV. For twelve more states the branching ratios, although not yet determined, are expected to be small. The gamma-ray emission from other individual nuclear states is not likely to be as great as that that for the 15.11 MeV state in C-12.
    Keywords: SPACE RADIATION
    Type: Gamma Ray Spectry. in Astrophys.; p 323-329
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  • 8
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    Galactic center iron line emission (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Data from the Goddard Space Flight Center experiment on HEAO 1 were examined for galactic center iron line emission. Evidence for a 6.8 keV line from the summed flux within 10 deg longitude and 10 deg latitude of the galactic center was found; however, firm limits cannot be put on the intrinsic line width. If the line emission is diffuse and cosmic-ray-induced, the calculations of Bussard et al (1978) yield an upper limit to c-12 4.44 MeV line emission, which is not inconsistent with the results of Haymes et al (1975). Significant contributions to the iron line from discrete sources can not be ruled out.
    Keywords: SPACE RADIATION
    Type: Gamma Ray Spectry. in Astrophys.; p 302-309
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  • 9
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    Planetary gamma-ray spectroscopy (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The measured intensities of certain gamma rays of specific energies escaping from a planetary surface can be used to determine the abundances of a number of elements. The fluxes of the more intense gamma-ray lines emitted from 32 elements were calculated using current nuclear data and existing models for the source processes. The source strengths for neutron-capture reactions were modified from those previously used. The fluxes emitted form a surface of average lunar composition are reported for 292 gamma-ray lines. These theoretical fluxes were used elsewhere to convert the data from the Apollo gamma-ray spectrometers to elemental abundances and can be used with measurements from future missions to map the concentrations of a number of elements over a planet's surface. Detection sensitivities for these elements are examined and applications of gamma-ray spectroscopy for future orbiters to Mars and other solar-system objects are discussed.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 98-148
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  • 10
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    Jovian S-burst observations at 32 MHz (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Drift rates for S-burst emissions from Jupiter are studied. The burst spectra, recorded in the frequency range near 32 MHz, provide a qualitative illustration of the behavior of electron bunches shortly after injection into the Io-associated magnetic flux tube. The morphology of the spectra may be taken as support for the hypothesis of an ionospheric acceleration mechanism influencing the flow of electrons.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 272; Mar. 2
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  • 11
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    Possible fossil H2O liquid-ice interfaces in the Martian crust (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The extensive chaotic and fretted terrains in the equatorial regions of Mars are explained on the basis of the vertical distribution of H2O liquid and ice which once existed in the crust. This account assumes that below the permafrost containing water ice, there was a second zone in which liquid water resided for at least a time. Diagenetic alteration and cementation characterized the material in the subpermafrost zone; above, pristine fragmented material with various ice concentrations was found. Later, the ice-laden zone was stripped away by a number of erosional processes, exposing the former ice-liquid water interface.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 34; June 197
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  • 12
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    Global color variations on the Martian surface (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Spectral reflectance data from the Viking-II Orbiter vidicon cameras have provided a means of mapping and classifying Martian surface materials over about 65% of the planet. The imagery, acquired at three wavelengths, was processed to remove an average Martian photometric function; albedo maps at the three wavelengths were created. Analysis of the imagery showed that the dark region between the equator and about 30 deg S in the Martian highlands consists of ancient ridges, crater rims and rugged plateaus which are very red, and younger intercrater volcanic plains exhibiting mare ridges which are much less red. In addition probable eolian deposits were found in the intermediate and high albedo regions.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 34; June 197
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  • 13
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    Diffuse gamma radiation (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Results are reported for an investigation of the intensity, energy spectrum, and spatial distribution of the diffuse gamma radiation detected by SAS 2 away from the galactic plane in the energy range above 35 MeV. The gamma-ray data are compared with relevant data obtained at other wavelengths, including 21-cm emission, radio continuum radiation, and the limited UV and radio information on local molecular hydrogen. It is found that there are two quite distinct components to the diffuse radiation, one of which shows a good correlation with the galactic matter distribution and continuum radiation, while the other has a much steeper energy spectrum and appears to be isotropic at least on a coarse scale. The galactic component is interpreted in terms of its implications for both local and more distant regions of the Galaxy. The apparently isotropic radiation is discussed partly with regard to the constraints placed on possible models by the steep energy spectrum, the observed intensity, and an upper limit on the anisotropy.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 222
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  • 14
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    Saturn's rings: Particle composition and size distribution as constrained by microwave observations. I - Radar observations (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The radar backscattering characteristics of compositional and structural models of Saturn's rings are calculated and compared with observations of the absolute value, wavelength dependence, and degree of depolarization of the rings' radar cross section (reflectivity). The doubling method is used to calculate reflectivities for systems that are many particles thick using optical depths derived from observations at visible wavelengths. If the rings are many particles thick, irregular centimeter- to meter-sized particles composed primarily of water ice attain sufficiently high albedos and scattering efficiencies to explain the radar observations. In that case, the wavelength independence of radar reflectivity implies the existence of a broad particle size distribution; a narrower size distribution is also a possibility. Particles of primarily silicate composition are ruled out by the radar observations. Purely metallic particles may not be ruled out on the basis of existing radar observations. A monolayer of very large ice 'particles' that exhibit multiple internal scattering may not yet be ruled out.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 33; Feb. 197
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  • 15
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    Modification of fresh crater landforms - Evidence from the moon and Mercury (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The morphology of fresh lunar and Mercurian craters provides insight into processes of crater formation and modification. Measurements determined for Mercurian craters and compared to previously presented lunar data are depth/diameter, central peak and wall-related mass movement frequencies as functions of diameter, crater rim wall width/rim diameter, rim diameter/floor diameter, and central peak height/rim diameter. Two important results are as follows: (1) there is no evidence for direct gravity scaling of crater morphology, although some slight scaling relationship may be indicated, and (2) mass movements are responsible for the change in depth/diameter relationship observed near 2-km depth and 10-km diameter. The latter result is helpful in explaining gravitational and topographic data which suggest low-density regions beneath large fresh craters.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 83; Jan. 10
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  • 16
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    Minor planets and related objects. XXV - UBV photometry of 145 faint asteroids (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Magnitudes and colors on the UBV system are presented for 145 minor planets, including 31 objects in the Eos family, 14 in the Koronis family, 6 in the Nysa family, 11 in the Themis family, 4 Hungarias, 7 Hildas, 8 Trojans, and several objects in unusual orbits. Clearly defined color groups for the Eos, Koronis, Nysa, and Themis family members are strongly suggestive of origin from discrete parent bodies. The Nysas apparently show large light-curve amplitudes. The Mars-orbit crossers 1977RA and 1980 = 1950LA, the earth-orbit crosser 1976UA, and several main-belt asteroids are found to show peculiar colors of unknown significance. The Mars-orbit crosser 1916 = 1953RA appears to be a typical S object, while 1474 Beira and 1977VA show neutral colors. Asteroids at semimajor axis in excess of 4 AU (Trojans preceding and following Jupiter, 279 Thule, and 944 Hidalgo) all belong to a color group centered at B-V = 0.72, U-B = 0.24.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomical Journal; 83; June 197
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  • 17
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    High resolution spectroscopy from low altitude satellites (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The P 78 1 satellite to be placed in a synchronous polar orbit at an altitude of 550-660 km will carry two identical high resolution spectrometers each consisting of a single (approximately 85 cc) intrinsic germanium IGE detector. The payload also includes a pair of phoswitch scintillators, an array of CdTe detectors and several particle detectors, all of which are mounted on the wheel of the satellite. The intrinsic high purity IGE detectors receive cooling from two Stirling cycle refrigerators and facilitate the assembly of large and complex detector arrays planned for the next generation of high sensitivity instruments such as those planned for the gamma ray observatory. The major subsystems of the spectrometer are discussed as well as its capabilities.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 529-540
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  • 18
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    Theory of the accretion column and cyclotron radiation in X ray pulsars (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The energetics of the decelerating matter in the accretion column of X-ray pulsars is considered, in particular the Coulomb process. A two zone model is presented to account for the continuum and cyclotron line emission, incorporating a fan-beam radiation scheme, which appears able to explain the observed properties.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 425-433
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  • 19
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    Cyclotron emission in neutron star magnetospheres (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Kinematic aspects of cyclotron emission in superstrong magnetic fields are reviewed to suggest characteristic features which might be useful in confirming the nature of the reported line feature near 50 keV in the spectrum of Her X-1. The role of the inverse process of cyclotron absorption is also discussed.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 394-403
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  • 20
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    Measurements of 15.11-MeV gamma-ray flux produced in the reactions C-12(p, p')-C-12*(15.11 MeV) and O-16(p, p' alpha)-C-12*(15.11 MeV) (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The flux of 15.11 MeV gamma rays relative to the flux of 4.44 MeV gamma rays which are emitted from the corresponding states of C-12 are a sensitive measure of the spectrum of exciting particles in solar flares and other cosmic sources. Emission of 15.11 MeV gamma rays may result not only from the direct excitation of C-12 but also from the interaction O-16 (p,p' alpha) C-12* sup 15.11 MeV. Although the cross sections for the direct reaction was studied extensively, the cross section for the spallation interaction with O-16 is not reported in the literature. Preliminary measurements demonstrated the feasibility of measuring the production of 15.11 MeV gamma rays by proton interactions with O-16 using the University of Maryland cyclotron facility. For both carbon and oxygen targets the flux of 15.11 MeV gamma rays is being measured relative to the flux of 4.44 MeV gamma rays. The gamma ray emission from de-excitation of the giant dipole resonances is being measured.
    Keywords: SPACE RADIATION
    Type: Gamma Ray Spectry. in Astrophys.; p 502-511
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  • 21
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    Confidence about line features in Her X-1 spectrum (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A balloon borne X-ray telescope was flown Aire-surl'Adour, France to search for pulsation of the X-ray source HER X1. The source was measured for about 3500 s relative exposure larger than 0.75 and features were detected at 57.5 plus or minus 7.5 keV and 135 plus or minus 10 keV in the spectrum. Data were reanalyzed in terms of possibility of gain shift encoder. The very strong dependence of the line features on such a shift is discussed.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 346-370
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  • 22
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    Gamma-ray lines from neutron stars as probes of fundamental physics (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The detection of gamma-ray lines produced at the surface of neutron stars will serve to test both the strong and gravitational interactions under conditions unavailable in terrestrial laboratories. Observation of a single redshifted gamma-ray line, combined with an estimate of the mass of the star will serve as a strong constraint on allowable equations of state of matter at supernuclear densities. Detection of two redshifted lines arising from different physical processes at the neutron star surface can provide a test of the strong principle of equivalence. Expected fluxes of nuclear gamma-ray lines from accreting neutron stars were calculated, including threshold, radiative transfer and redshift effects. The most promising probes of neutron star structure are the deuterium formation line and the positron annihilation line. Detection of sharp redshifted gamma-ray lines from X-ray sources such as Cyg X-1 would argue strongly in favor of a neutron star rather than black hole identification for the object.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 275-282
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  • 23
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    The accretion of planets from planetesimals (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Collisional accretion appears to be a viable, and seemingly unavoidable, mechanism for intermediate-stage from a swarm of planetesimals into a system containing a few discrete seed planets. Some other mechanism must be invoked to explain growth of condensate grains up to at least tens of meters. Gravitational instability in the particulate disk seems a plausible means of achieving that early-stage growth up to kilometer-scale bodies. The last stage of growth in which the seed planets accrete the remaining material now presents difficulties due to the isolated, circular orbits generated from the intermediate collisional stage.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 24
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    Isotopic anomalies in solar system material - What can they tell us (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Three relatively recently discovered anomalies are considered. The goal of isotopic research is to understand what phenomena are responsible for the observed isotopic anomalies, and thereby to determine the initial solar system isotopic composition. Until recently there has been no measured isotopic ratios which could not be understood in the context of reasonable physical or chemical processes acting to alter a uniform initial solar isotopic composition. This situation changed in 1969 with the discovery by Black and Pepin of an unusual neon isotopic composition in certain carbonaceous meteories. This unusual composition was later designated as Neon E. An unusual or anomalous oxygen isotopic composition was discovered by Clayton et al. (1973). A magnesium isotopic anomaly was discovered by Gray and Compston (1974), and Lee and Papanastassiou (1974). The three isotopic anomalies are discussed, emphasizing particularly the experimental evidence, possible causes for the observed isotopic composition and finally, possible implications of these anomalies with regard to models of solar system formation and evolution.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 25
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    Far infrared spectrophotometry of Jupiter and Saturn (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Infrared spectral measurements of Mars, Jupiter, and Saturn were obtained from 100 to 470 kaysers and, by taking Mars as a calibration source, brightness temperatures of Jupiter and Saturn were determined with approximately 5 kayser resolution. Internal luminosities were determined from the data and are reported to be approximately 8 times 10 to the minus tenth power of the sun's luminosity for Jupiter and approximately 3.6 times 10 to the minus tenth power of the sun's luminosity for Saturn. Comparison of data with spectra predicted by models suggests the need for an opacity source in addition to gaseous hydrogen and ammonia to help explain Jupiter's observed spectrum in the vicinity of 250 kaysers.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 35; July 197
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  • 26
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    A microstructural study of the Tishomingo meteorite (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Metallography, electron microscopy, and X-ray diffraction techniques were employed to study a fragment of the Tishomingo iron meteorite. The results suggest the following thermal-mechanical history: The fragment was originally a large crystal of taenite (gamma). Cooling through the alpha + gamma phase boundary did not result in accompanying precipitation of kamacite (alpha). Transformation to a martensitic structure initiated between -25 and -65 C. Transformation continued as the temperature fell to -75 to -115 C, resulting in approx 80% martensite (alpha-prime). Subsequent shock deformation and thermal aging processes substantially modified the taenite and martensite microstructures. Twins in the retained taenite phase are attributed to shock deformation at a pressure estimated for a single event at about 170 kbar. The existing complex altered martensite structure containing both taenite and kamacite (3-15% Ni) particles was apparently the product of both shock deformation and thermal aging processes. The maximum temperature reached during thermal aging is estimated to be less than 400 C and perhaps below 310 C.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 42; July 197
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  • 27
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    The tektite problem (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Small glassy pebbles, called tektites, are found in widely scattered locations around the world. These tektites appear much like volcanic glass obsidian, but their chemical composition is different from that of any terrestrial lava and they contain far less water and none of obsidian's characteristic microcrystals. No one has ever found the mother lode of a field of tektites. They cannot, therefore, be the product of terrestrial volcanism. Recently acquired knowledge about the moon's surface confirms earlier indications that tektites cannot be bits of lunar soil propelled to the earth by the impact of meteorites on the moon. According to one of two remaining possibilities tektites are bits of terrestrial sedimentary rock excavated by meteorites striking the earth's surface, melted by the heat of impact, and congealed into glass as they travel above the atmosphere to the scattered sites where they are found. The other possibility is that tektites are the remains of gobs of lava fired at the earth by volcanic activity on the moon.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Scientific American; 239; Aug. 197
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  • 28
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    Comment on 'Spectrophotometric and color estimates of the Viking lander sites' by Friedrich O. Huck et al (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 83; July 10
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  • 29
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    Conclusions derived from the evidence on accretion in meteorites (1978)
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    Publication Date: 2011-08-17
    Description: A study of the evidence on accretion in meteorites shows that gross chemical features of chondritic meteorite type were established by accretion of materials with characteristic chemical and isotopic compositions. Some meteorites have been subjected to intensive mechanical and/or thermal processes. Mixing has occurred among meteorite types, presumably late in the accretion sequence. From the materials which appear to have escaped substantial modification it can be concluded that the relative velocities between accreting grains varied but in some cases were very low. Accretion took place after most, if not all, of the gaseous components had been separated from the condensed portion of solar matter.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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    Chemical alterations of the Holbrook chondrite resulting from terrestrial weathering (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Major, minor and trace element analysis as well as noble gas measurements were performed on three Holbrook chondrite samples collected fresh in 1912, in 1931, and in 1968. Decreases in metallic iron and MgO and an increase in total iron were detected. Elemental concentrations of Ti, Ca, Al, P, Mn, Ni, and Cr did not change significantly during weathering. While sodium might have been lost, and K slightly enriched, the trace elements C, Rb, and Sr increased at least two-fold during weathering. Gas abundances decreased, and the concentration ratios of noble gas nuclides varied unpredictably.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics; 13; Sept. 30
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  • 31
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    The origin of planetary atmospheres (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Reasons for the difference in planetary atmospheres are reviewed. Atmospheric formation by outgassing from terrestrial planets is contrasted with the retention of the primary material by the outer planets. The differences in Venusian, earth, and Martian atmospheres are explained in terms of planet distance from the sun. Data on terrestrial planet pressures, temperatures, and gas compositions, as well as on rates and gas composition of outgassing material are presented. The significance of planet mass is considered.
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    The phase function of Venus cloud particles from Mariner 10 data (1978)
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    Publication Date: 2011-08-17
    Description: Mariner 10 images of Venus taken at several phase angles were photometrically reduced. The analysis shows that the phase function of the cloud particles is not isotropic, as had been deduced earlier from the brightness distribution on spacecraft images taken at a single phase angle, but has a broad minimum near 60 deg and is forward-scattering. The scattering properties are in quantitative agreement with previous deductions from earth-based polarization measurements by Hansen and his associates.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 5; Dec. 197
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  • 33
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    The ammonia mixing ratio in Jupiter's stratosphere (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The paper describes the theory that underlies the model calculations which show that the far-infrared bands of ammonia are very sensitive to the ammonia distribution above the Jovian atmospheric inversion layer. Observation of the J = 5 and J = 6 ammonia bands at moderate resolution might permit choice between a cold trap model or the irreversible uv photodestruction model for the ammonia distribution. The lack of prominent emission cores in the NH3 rotation-inversion lines only implies that the mixing ratio is low. The ammonia is uniformly mixed if the inversion temperature is low but, at a higher inversion temperature, emission cores will be observed unless the photodissociation is extremely efficient down to at least the inversion layer.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 36; Oct. 197
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    The Allende meteorite - Evidence for a new cosmothermometer based on the Ti/3+/ to Ti/4+/ ratio (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The mineral thermodynamic condensation sequence is applied to assemblages in Ca-Al-Ti-rich inclusions in the Allende meteorite, and it is suggested that the total amount of titanium and Ti(3+) contents of aluminous clinopyroxenes (fassaites) are temperature sensitive and that the ratio Ti(3+)/Ti(4+) may be used as a qualitative cosmothermometer. The direct gas-to-solid condensation hypothesis is favored because the predicted thermodynamic sequence is followed. Thermodynamic calculations indicate that the condensation interval of Ti(3+) stabilization is 1647-1125 K, while the titanian-fassaites probably condensed in the interval 1625-1349 K. It is suggested that the Allende meteorite has sampled a spectrum of the condensing solar nebula.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 276; Nov. 16
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  • 35
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    Nitric oxide production by Tunguska meteor (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The nonequilibrium chemical processes of nitric oxide formation are computed for the wake of the Tunguska meteor of 1908. The wake characteristics are derived by carrying out an optically-thick radiation field analysis for ablation of the meteoroid. The wake flow field is approximated by a one-dimensional, well-stirred reactor model. Known characteristics of the Tunguska event are imposed as constraints, and three controlling parameters - chemical composition, density, and velocity - are varied over a range around the values derived by Korobeinikov et al. (1976) and Petrov and Stulov (1975). The calculation shows that at least 19 million tons of nitric oxide is produced between the altitudes of 10 and 50 km. The anomalous atmospheric phenomena following the event are attributed to the reactions involving nitric oxide thus produced and atmospheric ozone. It is speculated that the nitric oxide produced by the event fertilized the area near the fall, causing the observed rapid plant growth.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Acta Astronautica; 5; July-Aug
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  • 36
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    Relative abundance of antiprotons and antihelium in the primary cosmic radiation (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The paper reports measurement of the antiproton-to-proton and antihelium-to-helium ratios in the 4-100 GeV/c range. A superconducting magnet spectrophotometer obtained the data during a balloon flight in May 1976. The upper limit value for the antiproton ratio is 0.0005 in the 4.2-12.5 GeV/c range. This value is only slightly higher than the expected value for a leaky box-model and nearly equal to the value expected in the Peter-Westergard model. It is suggested that this upper limit value rules out the closed galaxy model. Upper limit values for the antihelium ratio are 0.000058 in the 4-10 GeV/c range; less than 0.0001 in the 4-33 GeV/c range; and less than 0.01 in the 33-100 GeV/c range. The interpretation of the raw data is explained.
    Keywords: SPACE RADIATION
    Type: Nature; 274; July 13
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  • 37
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    Asteroid 1 Ceres - Evidence for water of hydration (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: An absorption feature centred near 3.0 microns has been discovered in the infrared spectrum of asteroid 1 Ceres. This spectrum has been compared with laboratory spectra of meteorites and shows great similarity to the spectra of type II carbonaceous chondrites. By analogy this suggests the presence of about 10-15 per cent water in the form of water of hydration on the surface of Ceres. This is the first evidence of water in the surface material of an asteroid.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Royal Astronomical Society; vol. 182
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  • 38
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    Circular polarization of sunlight reflected by planetary atmospheres (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Multiple scattering calculations are performed in order to investigate the nature of the circular polarization of sunlight reflected by planetary atmospheres. Contour diagrams as a function of size parameter and phase angle are made for the integrated light from a spherical but locally plane-parallel atmosphere of spherical particles. To investigate the origin of the circular polarization, results are also computed for second-order scattering and for a simpler semiquantitative model of scattering by two particles. Observations of the circular polarization of the planets are presently too meager for accurate deduction of cloud particle properties. However, certain very broad constraints can be placed on the properties of the dominant cloud particles on Jupiter and Saturn. The cloud particle size and refractive index deduced for the Jupiter clouds by Loskutov, Morozhenko, and Yanovitskii from analyses of the linear polarization are not consistent with the circular polarization. The few available circular polarization observations of Venus are also examined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 33; Jan. 197
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  • 39
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    The composition of Phobos - Evidence for carbonaceous chondrite surface from spectral analysis (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: In connection with a need for more definitive information concerning the composition of Phobos in a study of its origin, an ultraviolet-visible-infrared reflectance spectrum of the Martian satellite was compiled from the Mariner 9 ultraviolet spectrometer, Viking lander imaging, and ground-based photometric data. The probable surface composition of Phobos was deduced by comparing the obtained spectrum with the spectra of asteroids of known composition. The considered data show that the reflectivity of Phobos is flat from 1100 to 400 nm but decreases sharply in the ultraviolet to about 1 percent at 212 nm. The reflectance spectrum is similar to the spectra of asteroids Ceres and Pallas which were found to have surface compositions similar to that of carbonaceous chondrites. It is concluded that the surface composition of Phobos is also similar to that of carbonaceous chondrites. The results of the investigation point to different modes of origin for Mars and Phobos.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 199; Jan. 6
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  • 40
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    Viking first encounter of Phobos - Preliminary results (1978)
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    Publication Date: 2011-08-17
    Description: Viking Orbiter-1 (VO-1) made a series of close flybys of the Martian satellite Phobos in February and May 1977. A description is presented of the results obtained during the flybys in February. The flyby geometries for the encounter period in February are shown in a graph. The trajectory design gave flybys on the illuminated side of Phobos within 80 to 300 km during the entire encounter period. The primary encounter observations of Phobos included visual and infrared imaging as well as radio tracking of VO-1 while it was under the gravitational influence of Phobos. Visual imaging was obtained from two narrow-angle television cameras. Infrared observations were obtained from an infrared thermal mapper. Radio data included S- and X-band Doppler and ranging data to VO-1 with a 10-second Doppler count. Assuming for Phobos a volume of 500 + or - 900 cu km, a mean density of 1.9 + or - 0.6 g/cu cm is obtained for it on the basis of the processed data.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 199; Jan. 6
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  • 41
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    The origin and relative abundances of C, N and the noble gases on the terrestrial planets and in meteorites (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Relative concentrations of noble gases and C and N are evaluated for the terrestrial planets. Comparisons between amounts of volatile materials in carbonaceous chondrites and on Earth and Mars are presented as support for the accretion model of planetary formation. However, attention is given to the large differences in the C/noble gas ratios on various bodies in the solar system, e.g. the Sun, Venus, Earth, Mars, stressing that the data are too incomplete to provide a reliable model for the sources of volatile and noble elements on the terrestrial planets.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 271; Jan. 12
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  • 42
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    Multicolor observations of Phobos with the Viking lander cameras - Evidence for a carbonaceous chondritic composition (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The reflectivity of Phobos has been determined in the spectral region from 0.4 to 1.1 micrometers from images taken with a Viking lander camera. The reflectivity curve is flat in this spectral interval and the geometric albedo equals 0.05 + or - 0.01. These results, together with Phobos's reflectivity spectrum in the ultraviolet, are compared with laboratory spectra of carbonaceous chondrites and basalts. The spectra of carbonaceous chondrites are consistent with the observations, whereas the basalt spectra are not. These findings raise the possibility that Phobos may be a captured object rather than a natural satellite of Mars.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 199; Jan. 6
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    The ISEE-C gamma ray burst spectrometer (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The technical properties, operation, and expected sensitivity are discussed for an experiment intended to search for narrow lines in the spectra of gamma ray bursts during the ISEE-C mission. At the heart of the experiment is a radiatively cooled germanium solid state photon detector. The instrumentation is capable of storing the entire spectrum of all but the largest bursts in the energy range 0.05-6.5 MeV. In addition, it analyzes the signals from two CsI detectors in two other experiments on the spacecraft and records event time histories from these to a few millisecond accuracy. A background mode permits spectral analysis during quiet times and will allow the determination of physically interesting upper limits for narrow lines in the diffuse gamma ray background radiation.
    Keywords: SPACE RADIATION
    Type: Gamma Ray Spectry. in Astrophys.; p 516-528
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  • 44
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    The excitation of electronic transverse energy levels in an intense magnetic field (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Observations of the X-ray pulsar Hercules X-1 show a line emission feature at about 60 keV, which has been interpreted as the fundamental electron cyclotron line in a magnetic field of around six trillion gauss. In this interpretation, the line radiation results from transitions between transverse energy levels, which are quantized by the field. The expected line luminosity from the excitation of these levels by protons which are falling into the polar cap of a neutron star are calculated. They are assumed to attain kinetic energies up to around 200 MeV, the gravitational potential energy at the surface. The cross sections for high energy Coulomb encounters between small pitch angle protons and electrons in a strong field are measured and used to calculate the energy loss rate of the infalling protons. This rate, together with the rate of elastic nuclear proton collisions, is then used to calculate the number of line photons an infalling proton can be expected to produce, directly or indirectly. The results are applied to Hercules X-1.
    Keywords: SPACE RADIATION
    Type: ma Ray Spectry. In Astrophys.; p 404-417
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  • 45
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    Cyclotron lines from Her X-1 (1978)
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    Publication Date: 2011-08-17
    Description: Data obtained during four balloon flight observations of hard X-ray emission from Her X-1 provide strong support for the existence of a spectral line feature at 54 keV to 58 keV, while the existence of a second harmonic is uncomfirmed. Because it is difficult to explain the observed feature by a second continuum spectrum or by atomic or nuclear processes, an interpretation in terms of a cyclotron line seems likely. There are two possibilities. There may be a cyclotron absorption feature at approximately 42 keV, and a possible second one at approximately 80 keV. In particular there may be a rather broad absorption feature between the spectral break (25 keV) and approximately 40 keV.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 331-345
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  • 46
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    Gamma ray spectroscopy in astrophysics: Solar gamma ray astronomy on solar maximum mission (1978)
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    Publication Date: 2011-08-17
    Description: The SMM gamma ray experiment and the important scientific capabilities of the instrument are discussed. The flare size detectable as a function of spectrum integration time was studied. A preliminary estimate indicates that a solar gamma ray line at 4.4 MeV one-fifth the intensity of that believed to have been emitted on 4 August 1972 can be detected in approximately 1000 sec with a confidence level of 99%.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 558-574
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  • 47
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    Search for broad gamma ray lines with the UCR double Compton scatter telescope (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The operation of a double scatter telescope and the evaluation of data obtained during a 24 hour balloon flight are discussed. An increase in gamma rays was observed as the galactic anti-center crossed the aperature of the telescope. Searches for lines from p(n,gamma)d at 2.2 MeV, C-12* at 4.4 MeV and on -16* at 6.1 MeV and for other lines broadened or redshifted are being conducted to identify the processes responsible for the production of celestial gamma rays. Two upper limits for lines in the angalactic anti-center direction at 4.4 MeV and 6.1 MeV are 6 and 4 x 10 to the minus 4 power gamma/sq cm-s.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 217-222
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  • 48
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    Nuclear gamma rays from stellar flares (1978)
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    Publication Date: 2011-08-17
    Description: Solar flare observations are consistent with the phenomenological description that a loop of magnetic flux is convected to the surface of the star and twisted. The resulting inductive current parallel to the field is dissipated at an enhanced rate throughout the field volume by current limiting instabilities. The steady state balance between joule heating and thermal conduction along the field lines of force to the denser, cooler surface establishes a temperature distribution. The expansion of heated and ionized surface layers leads to a pressure balance and hence predictable density and X-ray emission measure. The current limitation instabilities result observationally in the parallel current being transferred to run-away ions that reach a kinetic energy of some finite fraction of the inductive potential drop. The nuclear excitation gamma rays produced by such a run-away ion current are calculated for a white dwarf flare.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 149-167
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    Mechanisms and sites for astrophysical gamma ray line production (1978)
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    Publication Date: 2011-08-17
    Description: The production of gamma ray lines and estimates of line fluxes resulting from nuclear deexcitations, positron annihilation, and electron capture at various astrophysical sites are discussed. Supernova and nova explosions synthesize long-lived radioactive isotopes and eject them into space where they produce observable gamma ray lines by decaying into excited levels of daughter nuclei or by emitting positrons. Energetic charged particles in the interstellar medium, in supernova remants, in solar or stellar flares, and possibly in the vicinity of compact objects, produce gamma-ray lines by inelastic collisions which either excite nuclear levels or produce positrons and neutrons. Energetic particles can result from acceleration in time-varying magnetic fields (solar flares) or from gravitational accretion onto neutron stars and black holes. Electromagnetic processes in the strong magnetic fields of pulsars can produce positron-electron pairs, with line emission resulting from positron annihilation. Deexcitations of quantized states in strong magnetic fields can also produce lines.
    Keywords: SPACE RADIATION
    Type: Gamma Ray Spectry. in Astrophys.; p 7-41
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  • 50
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    The transfer of cyclotron lines through the magnetospheric shell of Hercules X-1 (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Cyclotron emission from a strong magnetic field, has been proposed to identify line feature observed in the hard X-ray spectrum of the neutron star Hercules X-1. If this interpretation is indeed correct, and if the model wherein the 1.24 second hard X-ray pulse is due to the occultation of a more isotropic X-ray flux by an opaque magnetospheric shell is accepted then these observations can be used to place strict limits on the total source luminosity of the cyclotron emission. The observational fate of cyclotron line photons that have emerged from the region near the neutron star surface, but have yet to encounter an opaque shell at the magnetosphere is discussed. It is shown that if a narrow line is incident on such a shell, then a residual narrow feature can emerge from the shell.
    Keywords: SPACE RADIATION
    Type: Gamma Ray Spectry. in Astrophys.; p 418-424
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  • 51
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    Low energy gamma ray observations with the MPI-Compton telescope (1978)
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    Publication Date: 2011-08-17
    Description: Although the evaluation of data from the first balloon-flight of a large area Compton telescope is incomplete, two preliminary results are discussed. From the measured background spectrum at float altitude, the sensitivity of the telescope for the detection of cosmic gamma ray lines is estimated. The energy spectra is determined for an enhanced gamma ray flux observed from the direction of the Seyfert galaxy NGC 4151. A schematic drawing of the telescope is presented and discussed.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 207-216
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    Detection of 511 keV positron annihilation radiation from the galactic center direction (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A balloon-borne gamma ray telescope with an approximately 130 cu cm high purity germanium detector was flown over Australia to detect sharp spectral features from the galactic center direction. A 511 keV positron annihilation line was observed at a flux level of (1.21 plus or minus 0.22) x (10/cu cm) photons/sec/sp cm. Suggestive evidence for the detection of the three-photon positronium continuum is presented. The possible origin of the positrons is discussed.
    Keywords: SPACE RADIATION
    Type: NASA. Goddard Space Flight Center Gamma Ray Spectry. in Astrophys.; p 169-189
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  • 53
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    IAU nomenclature for albedo features on the planet Mercury (1978)
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    Publication Date: 2011-08-17
    Description: The International Astronomical Union has endorsed a nomenclature for the albedo features on Mercury. Designations are based upon the mythological names related to the god Hermes; they are expressed in Latin form. The dark-hued albedo features are associated with the generic term Solitudo. The light-hued areas are designated by a single name without generic term. The 32 names adopted are allocated on the Mercury map.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 34; Apr. 197
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    Io-phase motion and jovian decametre source locations (1978)
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    Publication Date: 2011-08-17
    Description: A second-order effect in the relationship between jovian decameter storms and the departure of Io from superior geocentric conjunction is explained on the basis of latitudinal variations in the earth-Jupiter viewing geometry. These variations are defined by the 12-year cycle in the jovicentric declination of the earth. In addition, it is found that the emission of the jovian decameter storm source Io-B (Io-C) is beamed from the northern (southern) magnetic latitudes. These conclusions are compatible with source positions derived from polarimetry and from considerations of planetary-limb shadowing.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 272; Mar. 23
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  • 55
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    Photometry and polarimetry of Jupiter at large phase angles. I - Analysis of imaging data of a prominent belt and a zone from Pioneer 10 (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Photopolarimetric observations of a prominent bright zone and a dark belt of Jupiter in red and blue light are analyzed which were performed by Pioneer 10 at phase angles of 12, 23, 34, 109, 120, 127, and 150 deg. Geometric and photometric reductions of the imaging data are described, the instrument sensitivity at various times is evaluated, and the data are referred to an absolute scale. The observations are analyzed in detail by comparing the data with results of radiative-transfer calculations for specific scattering models of Jupiter's atmosphere. These models include those with a vertical structure consisting of a layer of Rayleigh-scattering gas above a semiinfinite mixture of cloud particles and gas, those having a small quantity of aerosols in the gas above either the diffuse cloud in a reflecting-scattering model or the top cloud of a two-cloud-layer model, those in which a forward-scattering haze is mixed uniformly with gas, and those containing dust layers. It is found that in both the belt and the zone in red as well as blue light, cloud phase functions are required which provide both strong forward scattering and some backscattering.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 33; Mar. 197
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  • 56
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    Uranus and the shape of elliptical rings (1978)
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    Publication Date: 2011-08-17
    Description: It is reported that when the star SAO158687 passed behind the Uranus system, its light was occulted twice by the epsilon (fifth) ring of the planet. The first part of the ring to occult was about 100 km wide and the second part was about 40 km wide. The variable width of the ring is accounted for by differences in the orbital eccentricities of the individual particles composing the ring.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 272; Mar. 9
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  • 57
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    Computer simulation of the velocity diffusion of cosmic rays (1978)
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    Publication Date: 2011-08-17
    Description: Monte Carlo simulation experiments have been performed in order to study the velocity diffusion of charged particles in a static turbulent magnetic field. By following orbits of particles moving in a large ensemble of random magnetic field realizations with suitably chosen statistical properties, a pitch-angle diffusion coefficient is derived. Results are presented for a variety of particle rigidities and rms random field strengths and compared with the predictions of standard quasi-linear theory and the nonlinear partially averaged field theory.
    Keywords: SPACE RADIATION
    Type: Physics of Fluids; 21; Mar. 197
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    The occultation of Epsilon Geminorum by Mars as observed at Princeton (1978)
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    Publication Date: 2011-08-17
    Description: Results are reported for two-color (red and blue) high-speed photometric observations of the April 8, 1976, occultation of Epsilon Gem by Mars. The observing system is briefly described, fits to an isothermal atmospheric model of the event are presented, and the blue data are used to derive temperature profiles of the Martian atmosphere in the manner of Wasserman and Veverka (1973). The results are compared with those of Elliot et al. (1977), which were obtained from the NASA Kuiper Airborne Observatory.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomical Journal; 83; Apr. 197
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    Properties of the clouds of Venus, as inferred from airborne observations of its near-infrared reflectivity spectrum (1978)
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    Publication Date: 2011-08-17
    Description: The shape and absolute value of Venus' reflectivity spectrum is measured in the 1.2- to 4.0 micrometer spectral region with a circular variable filter wheel spectrometer having a spectral resolution of 1.5%. Comparing these spectra with synthetic spectra generated with a multiple-scattering computer code, a number of properties of the Venus clouds are inferred. Evidence is obtained indicating that the clouds are made of a water solution of sulfuric acid in their top unit optical depth, and that the clouds are made of this material down to an optical depth of at least 25. In addition, the acid concentration is 84 plus or minus 2% H2SO4 by weight in the top unit optical depth, the total optical depth of the clouds is 37.5 plus or minus 12.5, and the cross-sectional weighted mean particle radius lies between 0.5 and 1.4 micrometers in the top unit optical depth of the clouds. It is found that the average volume mixing ratio of H2SO4 and H2O contained in the cloud material both equal approximately 2 x 10 to the -6. Employing vapor pressure arguments, the acid concentration is shown to equal 84 plus or minus 6% at the cloud bottom and the water vapor mixing ratio beneath the clouds lies between 6 x 10 to the -4 and 10 to the -2.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 34; Apr. 197
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  • 60
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    Mercury's helium exosphere after Mariner 10's third encounter (1978)
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    Publication Date: 2011-08-17
    Description: From a comparison of the Mariner 10 third encounter UV spectrometer data with intensities generated from a newly constructed model exosphere, a new value of 4.5 x 10 to the -4th power for the fraction of the solar wind He(++) flux to be intercepted and captured by Mercury's magnetosphere, if the observed He atmosphere is maintained by the solar wind, has been derived. If an internal source for He prevails, the corresponding upper bound for the global outgassing rate is estimated to be 4.5 x 10 to the 22nd power/s. These values differ from those given earlier because of the present use of a surface temperature distribution satisfying the heat equation over Mercury's entire surface which employs Mariner-10-determined mean surface thermal characteristics. The mean standoff distance of Mercury's magnetopause averaged over Mercury's orbit is also used. Agreement between the observed and calculated intensities is found to be good. Minor discrepancies on the nightside of the terminator are explicable in terms of differences between actual and computed temperatures and scale height structure changes.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 83; Apr. 1
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  • 61
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    Is the moon really as smooth as a billiard ball - Remarks concerning recent models of sputter-fractionation on the lunar surface (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 5; Apr. 197
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  • 62
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    Acceleration of protons at 32 Jovian radii in the outer magnetosphere of Jupiter (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A rapid ten-fold increase of proton flux was observed at 32 Jovian radii in Jupiter's outer magnetosphere. The total event lasted about 30 minutes and was composed of many individual events. Both before and after the event, proton flux was similar to the low-flux level found between crossings of the magnetic equator. Measurements of angular distributions and the time histories of proton and alpha particle channels at different energies indicate that the flux increase is caused by local acceleration. It is suggested that the average particle population in the outer magnetosphere is caused by a state of dynamic equilibrium between acceleration and loss processes.
    Keywords: SPACE RADIATION
    Type: Journal of Geophysical Research; 83; Mar. 1
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  • 63
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    An analytic study of impact ejecta trajectories in the atmospheres of Venus, Mars, and earth (1978)
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    Publication Date: 2011-08-17
    Description: Calculations have been made to determine the effects of atmospheric drag and gravity on impact ejecta trajectories on Venus, Mars, and earth. The equations of motion were numerically integrated for a broad range of body sizes, initial velocities, and initial elevation angles. A dimensionless parameter was found from approximate analytic solutions which correlated the ejecta range, final impact angle, and final impact velocity for all three planets.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 33; Mar. 197
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  • 64
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    Investigation of the Manicouagan impact crater, Quebec - An introduction (1978)
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    Publication Date: 2011-08-17
    Description: An interdisciplinary study of the 65-km diameter Manicouagan ring structure in Quebec was undertaken to gain insight into the integrated effects of impacts on terrestrial planetary bodies. The paper serves as an introduction to several companion papers and summarizes major conclusions. Studies of the 214 m.y. old structure show that the melt rocks are texturally inhomogeneous but chemically homogeneous and can be modeled as a mixture of target lithologies. The melt rocks have a Sr-87/Sr-86 ratio compatible with the melting of crustal rocks. The melt had a two-stage cooling history with clast-melt interactions indicative of mixing superheated silicate liquid with cold clasts. Grain size, clast reactions, and thermal equilibration of clasts and melts are described.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 83; June 10
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  • 65
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    Partially averaged field approach to cosmic ray diffusion (1978)
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    Publication Date: 2011-08-17
    Description: A new nonlinear technique is used to derive the kinetic equation for particles interacting with turbulent fluctuations. Difficulties associated with quasi-linear theory are avoided. The new method evaluates the effects of the fluctuations along particle orbits which themselves include the effects of a statistically averaged subset of the possible configuration of the turbulence. As an illustration, the pitch-angle diffusion coefficient is calculated for particles interacting with 'slab model' magnetic turbulence, i.e., magnetic fluctuations linearly polarized transverse to a mean magnetic field. The pitch-angle diffusion coefficient is determined in the vicinity of 90-deg pitch angles where quasi-linear theory breaks down. The spatial diffusion coefficient parallel to a mean magnetic field is evaluated by use of the calculated pitch-angle diffusion coefficient. It is suggested that the partially averaged field method is not limited to small amplitude fluctuating fields and hence is not a perturbation theory.
    Keywords: SPACE RADIATION
    Type: Physics of Fluids; 21; Mar. 197
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  • 66
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    Effects of turbulence on average refraction angles in occultations by planetary atmospheres (1978)
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    Publication Date: 2011-08-17
    Description: Four separable effects of atmospheric turbulence on average refraction angles in occultation experiments are derived from a simplified analysis, and related to more general formulations by B. S. Haugstad. The major contributors are shown to be due to gradients in height of the strength of the turbulence, and the sense of the resulting changes in refraction angles is explained in terms of Fermat's principle. Because the results of analyses of such gradient effects by W. B. Hubbard and J. R. Jokipii are expressed in other ways, a special effort is made to compare all of the predictions on a common basis. We conclude that there are fundamental differences, and use arguments based on energy conservation and Fermat's principle to help characterize the discrepancies.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 34; May 1978
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  • 67
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    The rings of Saturn (1978)
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    Publication Date: 2011-08-17
    Description: Consideration is given to the development of theories concerning the rings of Saturn. Particular attention is given to ring structure, noting its thinness, the separations between rings, and observed variations in brightness. Data gathered via infrared, radio and radar techniques are described in terms of ring particle composition and size. Hypotheses about ring origin and evolution are outlined, including the tidal disruption model, calculations of Saturn's gravitational contraction history, grazing, and meteoroid bombardment. Prospects for future observations of Saturn's rings are reviewed, such as the variation in their radar reflectivity as a function of the tilt of the ring plane.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: American Scientist; 66; Jan
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  • 68
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    On the origin of Uranus' rings (1978)
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    Publication Date: 2011-08-17
    Description: The role of Miranda-Ariel orbital resonances in determining the structure of the rings of Uranus is discussed. In particular, it is argued that the three-body orbital resonances of Miranda and Ariel may function as a mechanism for the formation of narrow rings, rather than as a mechanism for trapping freely orbiting particles; the formation of narrow rings, in this hypothesis, would involve an inelastic collision process. The narrowness of the resonances may account for the sharply defined ring boundaries.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 272; Apr. 27
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  • 69
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    Photoelectrons and electron temperatures in the Venus ionosphere (1978)
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    Publication Date: 2011-08-17
    Description: Solar wind induced magnetic fields may be present in the dayside ionosphere of Venus. A scale analysis and detailed calculations of the effects of different field line orientations on photoelectron transport and electron temperature show that horizontal magnetic fields considerably alter the profiles of electron heating and temperature and photoelectron flux. Direct injection of solar wind electrons has been considered, and the effects are minor. No evidence is found to support the suggestion that a sharp gradient in electron temperature is the cause of certain features in the Mariner-10 electron density profile.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 83; May 1
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  • 70
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    Atomic hydrogen on Mars - Measurements at solar minimum (1978)
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    Publication Date: 2011-08-17
    Description: The Copernicus Orbiting Astronomical Observatory was used to obtain measurements of Mars Lyman-alpha (1215.671-angstrom) emission at the solar minimum, which has resulted in the first information on atomic hydrogen concentrations in the upper atmosphere of Mars at the solar minimum. The Copernicus measurements, coupled with the Viking in situ measurements of the temperature (170 plus or minus 30 K) of the upper atmosphere of Mars, indicate that the atomic hydrogen number density at the exobase of Mars (250 kilometers) is about 60 times greater than that deduced from Mariner 6 and 7 Lyman-alpha measurements obtained during a period of high solar activity. The Copernicus results are consistent with Hunten's hypothesis of the diffusion-limited escape of atomic hydrogen from Mars.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 200; June 2
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  • 71
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    The Martian satellites - 100 years on (1978)
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    Publication Date: 2011-08-17
    Description: Studies of Phobos and Deimos, the two satellites of Mars, may provide the best observations yet of the material populating the asteroid belt. Viking observations of Phobos showing crater chains and striations are analyzed, and Mariner-9 photometry exhibiting the albedo of the satellite is discussed. A mass determination for Phobos results in a value of 1.1 times 10 to the 19th power g; the mean density of the satellite is set at about 2 g per cu cm, a value suggesting formation of the satellite from material in the asteroid belt.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Royal Astronomical Society; vol. 19
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  • 72
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    Prairie Network fireballs. I - General information and orbits (1978)
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    Publication Date: 2011-08-17
    Description: Methods for obtaining and processing photographs of bright meteors in the United States in the period from 1963 to 1975 are briefly described. Orbital elements and other characteristics are given for 334 bright persistent and long Prairie Network fireballs. The accuracy of the data presented is evaluated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritika; 37, 1; 1978
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  • 73
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    The Yamato-74659 ureilite and some new findings on the Yamato achondritic pyroxenes (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A cube-like fragment with an approximately 4 mm edge was taken from the Yamato-74659 meteorite for the mineralogical and crystallographic examination discussed in the present paper. An analysis of powdered fragments by a standard wet chemical method showed that it matched to weathered ureilite. The chemical composition was found to differ from other ureilites in that the FeO content (8.83 wt%) is the lowest among known ureilites and it is richer in SiO2 contents (42.91 wt%).
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 74
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    Floor-fractured craters on the moon and Mars (1978)
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    Publication Date: 2011-08-17
    Description: Impact craters on the moon provided primary pathways for volcanic eruptions through shock-induced fractures that immediately or subsequently tap magma reservoirs. Evidence for this process includes unbreached lava-filled craters and fractured crater floors with associated eruptives. Over 200 craters with floor fractures have been identified on the moon. They commonly occur along the margins of irregular maria, thereby suggesting a link to this important phase of lunar volcanism. Topographic data reveal small elevation differences between the summit of the remnant central peaks and crater rim, and in many cases suggest that floor fracturing resulted from a tabular intrusion localized beneath the crater with uplift of the crater floor. A comparison of lunar and Martian crater photographs shows that some Martian craters also exhibit similar highly localized endogenic modifications.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 75
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    Aioun el Atrouss - Evidence for thermal recrystallization of a eurite breccia (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The Aioun el Atrouss meteorite is a breccia consisting largely of angular fragments of green orthopyroxene and containing scattered clasts of basaltic composition (mostly pigeonite and calcic plagioclase). It appears to be a physical mixture of two meteorite types - diogenite (hypersthene achondrite) and eucrite (basaltic achondrite). The results of a mineral analysis are tabulated, and typical pyroxene compositions in orthopyroxene (diogenite), subophitic and granoblastic portions of the meteorite are presented.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 76
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    Effect of the Mott cross section on the determination of the charge of ultraheavy cosmic rays from emulsion tracks (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Energy deposition due to secondary electrons is calculated as a function of distance from the axis of the track of a heavy ion. The calculation incorporates the empirical formulas of Kobetich and Katz (1968) for delta-ray energy dissipation. Both the Mott and Born-approximation expressions for the delta-ray energy distributions are used, and the results are compared. The energy deposition projected along a line perpendicular to the track is also calculated. These results are used to estimate the effect that the use of the Mott cross section would have in the interpretation of photometric measurements on emulsion tracks of trans-iron cosmic-ray particles. It is shown that the use of 50 keV as a characteristic track-formation electron energy to estimate the effect of the Mott cross section systematically overestimates charge as derived from emulsions for Z greater than 20.
    Keywords: SPACE RADIATION
    Type: Physical Review D - Particles and Fields; vol. 18
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  • 77
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    A determination of Jovian ammonia abundance based on a 2 micron spectrum (1978)
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    Publication Date: 2011-08-17
    Description: A spectrum of Jupiter in the two-micron region has been analyzed to determine the Jovian ammonia abundance. The result is approximately 4 cm-amagat, assuming an airmass factor of 2.5 and a single effective reflecting layer for this wavelength. This is compared with the abundances observed at other wavelengths.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 36; Dec. 197
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  • 78
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    Near-infrared spectra of the Galilean satellites - Observations and compositional implications (1978)
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    Publication Date: 2011-08-17
    Description: Reflectivity spectra of the trailing and leading sides of Io, Europa, Callisto, and Ganymede are analyzed which were obtained at an altitude of 41,000 ft from the Kuiper Airborne Observatory with circular variable filter-wheel spectrometers in the spectral region from 0.7 to 5.5 microns. The data are compared with laboratory spectrum and with synthetic spectra constructed on the basis of simple multiscattering theory. The 2.9-micron feature in Callisto's spectra is attributed primarily to bound water; the fractional amounts of water-ice cover on the trailing and leading sides of Ganymede and on the leading side of Europa are estimated. The bare-ground areas on Ganymede are shown to have reflectivity properties comparable to those of Callisto's surface in the studied spectral region, and the surfaces of both satellites are found to contain significant quantities of bound water. It is suggested that minor but significant amounts of ferrous-bearing material (either ferrous salts or alkali feldspars) can account for the 1.35-micron feature of Io.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 36; Dec. 197
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  • 79
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    Rare-gas-rich separates from carbonaceous chondrites (1978)
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    Publication Date: 2011-08-17
    Description: This paper describes an analysis of carbon-rich separates prepared by demineralization of colloidal fractions after disaggregation of bulk samples of the type C2 meteorites Murray, Murchison, and Cold Bokkeveld, as well as a methanol colloid extracted from acid-resistant residues of the Allende meteorite (type C3V) obtained by dissolution of most of the minerals in HCl and HF acids. The carbonaceous separates, or lAlates (a coined word designating colloids prepared sometimes before and sometimes after acid treatment), are characterized incompletely and with difficulty. A stepwise heating experiment on a Murray lAlate is discussed which revealed bimodal release of all noble gases, with similar patterns for Ar, Kr, and Xe. Chemical reactions are suggested as the likely mechanism for gas release. The results are shown to support the concept of a carbonaceous gas carrier uniformly present in meteorites of various types.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta; 42; Dec. 197
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  • 80
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    Gamma-ray astronomy and the origin of cosmic rays (1978)
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    Publication Date: 2011-08-17
    Description: Recent observations of cosmic gamma radiation are reviewed. It is shown that this radiation consists of an extragalactic background as well as a bright band of galactic radiation lying in the plane of the Milky Way and produced primarily by cosmic-ray collisions with interstellar gas atoms. The galactic gamma radiation is divided into a near component apparently associated with Gould's belt and a far component originating about 15,000 light years away and narrowly confined to the galactic plane. A Great Galactic Ring is identified which is 35,000 light years in diameter and in which most galactic cosmic rays are produced and supernovae and pulsars are concentrated. The physical mechanisms responsible for the production of most of the cosmic gamma rays in the Galaxy are examined, and the origin of galactic cosmic rays is considered. It is concluded that the cosmic rays are produced either in supernova explosions or in the pulsars they leave behind
    Keywords: SPACE RADIATION
    Type: American Scientist; 66; Sept-Oct
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  • 81
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    The dynamical evolution and origin of the Martian moons (1978)
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    Publication Date: 2011-08-17
    Description: The orbital evolution of Phobos and Deimos is considered from the standpoints of today's orbit, the semimajor axis, and eccentricity and inclination. The synchronous rotations of the moons are discussed, and attention is given to the origin (i.e., accretion and capture) of the moons.
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  • 82
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    Mariner 10 magnetic field observations of the Venus wake (1978)
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    Publication Date: 2011-08-17
    Description: The paper reports on an analysis of magnetic field observations by the Mariner 10 spacecraft during approximately a one-day period ending a few hours beyond Venus encounter on February 5, 1974. The magnetic field measurements are used to study the downstream region of the solar wind-Venus interaction over a distance of about 100 Venus radii. The study characterizes the various magnetic field regions encountered behind and near the planet; presents an argument that the magnetic field signatures observed are consistent with observation of either a steady or a transient wake, or at least the boundary region of such a wake, interior to a common sheath-like region; examines in detail the fluctuation and discontinuity features of these regions and compares them with those of the interplanetary medium; and summarizes how these new features contribute to the understanding of the solar wind-Venus interaction.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 83; Aug. 1
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  • 83
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    Odd nitrogen production by meteoroids (1978)
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    Publication Date: 2011-08-17
    Description: The process by which odd nitrogen species (atomic nitrogen and nitric oxide) are formed during atmospheric entry of meteoroids is analyzed theoretically. An ablating meteoroid is assumed to be a point source of mass with a continuum regime evolving in its wake. The amounts of odd nitrogen species, produced by high-temperature reactions of air in the continuum wake, are calculated by numerical integration of chemical rate equations. Flow properties are assumed to be uniform across the wake, and 29 reactions involving five neutral species and five singly ionized species are considered, as well as vibrational and electron temperature nonequilibrium phenomena. The results, when they are summed over the observed mass, velocity, and entry-angle distribution of meteoroids, provide odd-nitrogen-species annual global production rates as functions of altitude. The peak production of nitric oxide is found to occur at an altitude of about 85 km; atomic nitrogen production peaks at about 95 km. The total annual rate for nitric oxide is 40 million kg; for atomic nitrogen it is 170 million kg.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 83; Aug. 20
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  • 84
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    Global circulation and distribution of hydrogen in thermosphere of Venus (1978)
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    Publication Date: 2011-08-17
    Description: The global density distribution of atomic H in the upper atmosphere of Venus is determined in terms of a global circulation model. It is shown that H produced on the dayside is efficiently advected to the nightside by the major gas CO2 where it is then convected to lower altitudes and recombines. A maximum night/day H density ratio of about 5 is derived, in which case exospheric return flow from night to day strongly limits the nightside density enhancement. A previously postulated constraint connecting the eddy diffusion coefficient with the escape flux of H in one dimensional models is no longer required when global circulation of H is considered.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geophysical Research Letters; 5; Aug. 197
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  • 85
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    Intensity and pressure shift of the H2 /4,0/ S/1/ quadrupole line (1978)
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    Publication Date: 2011-08-17
    Description: Results are presented for two laboratory measurements of the intensity and central frequency of the (4, 0) S(1) quadrupole line of H2, which were made at pressures of 2.658 and 1.494 atm through a 0.456-km path length. It is found that the absolute line intensity is significantly lower than the value predicted from theoretical matrix elements but is essentially identical to the value derived by Rank et al. (1966). The central-frequency results are shown to verify the pressure shift predicted by McKellar (1974). It is concluded that hydrogen abundances estimated from the equivalent width of the (4,0) S(1) quadrupole line in the spectra of the outer planets will have to be revised upward by nearly a factor of 2.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 224
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  • 86
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    Spectrum of a fast sporadic meteor (1978)
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    Publication Date: 2011-08-17
    Description: The spectrum of a fast (63 km/s) sporadic meteor for which altitude and orbit data are available is reported. The -6 mag meteor occurred on January 5, 1976, over southern New Mexico. Fifty features have been identified in the spectrum. The spectrum is essentially identical to that of Perseid meteors of similar brightness. It is shown that heavy-particle collisions do not dominate bright meteor spectra lacking time resolution. Low-energy electron excitation of Ca II is strongly indicated in the wake to such an extent as to strongly affect spectra of this type lacking time resolution.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 224
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  • 87
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    The puzzling moons of Mars (1978)
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    Publication Date: 2011-08-17
    Description: Viking Orbiter observations of Phobos and Deimos are presented with attention to physical dimension and surface features. Both satellites are approximately 1.4 times as long as they are wide; Phobos having a length of 27 km, while Deimos is half that size. In addition, both satellites are tidally locked, as is earth's moon, and are held together by cohesive forces as well as by gravity. Phobos and Deimos are both heavily cratered, and Phobos has deep (30 m) grooves in the vicinity of its largest crater, Stickney; indicating surface fracturing under meteorite impact. The craters on Deimos are largely filled with a fine-grained substance, probably crater ejecta.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Sky and Telescope; 56; Sept
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    Recent advances in planetary magnetism (1978)
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    Publication Date: 2011-08-17
    Description: During the past decade, significant advances in the in situ measurements of planetary magnetic fields have been made. The U.S.A. and U.S.S.R. have conducted spacecraft investigations of all the planets, from innermost Mercury out to Jupiter. Unexpectedly, Mercury was found to possess a global magnetic field but neither the Moon nor Venus do. The results at Mars are incomplete but if a global field exists, it is clearly quite weak. The main magnetic field of Jupiter has been measured directly for the first time and confirms, as well as augments appreciably, the past 2 decades of ground-based radio astronomical studies which provided indirect evidence of the field. Progress in developing analytically complete models of the dynamo process suggests a possible common origin for Mercury, earth and Jupiter.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Moon and the Planets; 18; June 197
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  • 89
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    The cosmic gamma-ray background from the annihilation of primordial stable neutral heavy leptons (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The spectra and intensities of gamma radiation from (1) a homogeneous cosmic lepton background (2) a possible lepton halo around the Galaxy, and (3) integrated background radiation from possible lepton halos around other galaxies and from rich galaxy clusters are examined. Heavy-lepton annihilation radiation from the halos of other galaxies accounts for at most 0.005 of the background intensity, and the radiation from rich clusters account for at most 0.00005 of the background intensity. It is suggested that lepton annihilation fluxes from a galactic halo would be confused with cosmic-ray produced radiation and would therefore be difficult to observe. Radiation from a homogeneous cosmological lepton background might account for approximately 0.0001 of the observed cosmic gamma ray background. Energy spectrum and isotropy are considered.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 223
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  • 90
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    Mercury - Magnetic field and interior (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Present-day knowledge about the planetary magnetic field and interior of Mercury is reviewed. Radar observations are discussed which delineated the correct rotation rate of Mercury (58.646 days) and the planet's 3:2 spin-orbit resonance. The data obtained in Mariner 10 magnetic-field observations during the first and third encounters with Mercury are examined in detail, and theoretical studies of the planet's interior are summarized, including both steady-state models and those describing the thermal evolution of the planet. Two possible source mechanisms for the observed intrinsic planetary magnetic field are evaluated: an active dynamo and a passive paleomagnetic field frozen into the planet's outer layers at an earlier epoch. It is noted that neither the available magnetic-field data nor models of the planetary interior permit one to distinguish uniquely between the two mechanisms. The spin-orbit commensurability of Mercury is explained in the framework of the solar tides induced in the body of the planet, a nonaxisymmetric moment of inertia, and the highly eccentric orbit of the planet.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Space Science Reviews; 21; Mar. 197
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  • 91
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    The primitive solar accretion disk and the formation of the planets (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: The author develops the idea that the formation of the solar system was triggered by the explosion of a supernova near a compressed interstellar cloud, which was further compressed by the supernova ejecta until it went over the threshold for gravitational collapse. During the collapse it is expected that the cloud would fragment into much smaller pieces. The principle source of friction in the collapsing nebula is taken to be turbulent viscosity, the required stirring having been supplied possibly by meridional circulation currents. The theory can be shown to account for how a great deal of condensed matter in the form of cometary bodies could be put into elliptical orbits extending toward 100,000 AU, the region of the Oort reservoir.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 92
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    The expected frequency of doublet craters /A reply/ (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 35; Sept
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  • 93
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    1580 Betulia - An unusual asteroid with an extraordinary lightcurve (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Results of UBV photometry and polarimetry of 1580 Betulia during its 1976 apparition are presented. The synodic period of rotation is found to be 6.130 hr. The linear phase coefficient and absolute magnitude of the primary maximum in V are 0.032 mag/deg and 14.88, respectively. No color variations with rotation or solar phase angle were detected, the mean colors being B-V = 0.66 and U-B = 0.24. Betulia's light curve is unique among asteroids studied to date in that it displays three maxima and three minima within one rotational cycle, indicative of a region of greater roughness and/or a dark spot on one of its broad faces. Polarization results indicate a low albedo and a mean diameter of about 7 km, establishing Betulia as the first C-type asteroid to be found among the Mars crossers. A model accounting for most features of Betulia's light curve is given by a prolate spheroid rotating about one of its shorter axes having an axis ratio of 1:1.21 with a major topographic feature on one of its broad faces.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 35; Sept
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  • 94
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    Observations of medium-energy gamma-ray emission from the galactic center region (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Measurements of the gamma-ray emission in the medium-energy range between 15 and 100 MeV, obtained during two balloon flights from Brazil, are presented. The importance of this energy region in determining whether neutral-pion decay or electron bremsstrahlung is the most likely dominant source mechanism is discussed, along with the implications of such observations. Specifically, the data from this experiment suggest that emission from the galactic plane is similar to the theoretical spectrum calculated by Fichtel et al. (1976), including both source mechanisms but with the bremsstrahlung component enhanced by a factor of about 2. A spectral distribution of gamma-rays produced in the residual atmosphere above the instrument is also presented and compared with other data. A rather smooth spectral variation from high to low energies is found for the atmospheric spectrum.
    Keywords: SPACE RADIATION
    Type: Astrophysical Journal; vol. 225
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  • 95
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    IUE observations of solar system objects (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: During the scientific commissioning phase of IUE several spectra were acquired from objects residing in the Solar System. The activities focused on testing numerous parameters which would indicate the usefulness of IUE for planetary science. It seems that IUE can successfully tackle many important questions and the data analysis and interpretation of the initial set of observations has begun.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 275; Oct. 5
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  • 96
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    Nature of the atmospheric dynamics on Venus from power spectrum analysis of Mariner 10 images (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: Power spectrum analysis of Mariner 10 images for planetary zonal wavenumbers no less than 3 and for latitudes in the range 55 deg S to 25 deg N yields spectra which show a systematic and apparently significant variation with latitude. Accordingly, average spectra are determined for three latitude zones: an equatorial region, a midlatitude region, and an intermediate zone. A comparison of the results for Venus with brightness distribution spectra for terrestrial clouds reveals similarities between the Venus midlatitude region spectrum and that for the equatorial region of the earth. The only indication of a departure from a general power law behavior for the Venus spectra is a flattening of the equatorial spectrum in the region of wavenumbers 3 and 4. The characteristics of the Venus image spectra appear to be compatible with the interpretation that the observable clouds lie in a region of high static stability with the inertial eddy motions corresponding to two-dimensional turbulence.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of the Atmospheric Sciences; 35; Sept
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  • 97
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    Diffusion model for the upper atmosphere of Venus (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: On the basis of a linear theory it is shown that wind-induced diffusion associated with large-scale circulation in the Venus atmosphere leads to nighttime bulges in O, He, and H. The effect on He is very large with a 243-day rotation period of the atmosphere, yielding an upper limit for the maximum/minimum diurnal density ratio of approximately 1000. This ratio is much smaller for H (max/min of about 4) due to the greater importance of exospheric flow, which acts (as for He) as a damping mechanism. For the faster rotation period of 4 days consistent with the motions of the cloud tops, the diurnal variation of O is significantly reduced, contributing to an increase by a factor of two in the horizontal wind velocity. The same effect significantly reduces the He variations to an increase by a factor of 7 from day to night. The results suggest that composition and wind measurements provide valuable information on the rotation rate of the Cytherean thermosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 83; Sept. 1
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  • 98
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    Venus' rotation and atmospheric tides (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: On the basis of a presented theory, it is suggested that Venus' current rotation is a stable balance between atmospheric and solar body tides. The theory is concerned with Venus' atmospheric tides, driven by solar heating, and how these tides could serve as a third torque to balance the effects of solar body torque and to maintain a stable equilibrium resonance with regard to the earth's gravitational effects. In the absence of the atmospheric tidal torque, or some other torque, it would be expected that Venus would be despun until synchronous rotation (one side always facing the sun) is attained, rather than retain the retrograde rotation period of 243 days.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 275; Sept. 7
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  • 99
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    Fission origin of the moon - Cause and timing (1978)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: A new scenario is offered for the origin of the moon. It is assumed that the earth formed initially with about the maximum amount of angular momentum consistent with dynamical stability. This state is approximated by the secularly unstable Maclaurin spheroids (highly flattened hamburger-shaped bodies). It is shown that the earth cannot depart from this state at a reasonable rate as long as its viscosity is in the range of liquid rock. Since core formation supplies about 1600 kJ/kg, the earth will not leave this state until core formation is complete. When cooling produces a rise in viscosity, the earth will necessarily evolve along a path which is approximated by the Riemann ellipsoids (which have rapid internal motion). The evolution is toward a Jacobi ellipsoid, but it is intercepted by the development of a third-harmonic (pear-shaped) instability, which is catastrophic and leads to fission. The process of fission itself may be fundamentally analogous to the breaking of a wave in water. We cannot exclude the possibility that some other planets evolved similarly.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 35; Aug. 197
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  • 100
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    Diameters of the Galilean satellites from Pioneer data (1978)
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    Publication Date: 2011-08-17
    Description: Pioneers 10 and 11 have transmitted seven images of the Galilean satellites with surface resolutions on the order of several hundred kilometers. Because the point-spread function is well determined, it has been possible to measure the radius of each of the four satellites to a precision of typically plus or minus 30 km. The method used fits a semicircle to the illuminated limb by varying the center coordinates and radius until the best-fit criteria are satisfied. Careful attention is given to locating the true edge position within the blurred image. The radius determinations and corresponding densities for the satellites are: Io (1840 plus or minus 30, 3.41 plus or minus 0.19), Europa (1552 plus or minus 20, 3.06 plus or minus 0.15), Ganymede (2650 plus or minus 25, 1.90 plus or minus 0.06), and Callisto (2420 plus or minus 20, 1.81 plus or minus 0.05), where the units are in kilometers and grams per cubic centimeters, respectively.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 35; Aug. 197
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