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  • 1
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    Discrepancy in proton flux extrapolation along field lines in the middle Jovian magnetosphere (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: An attempt is made to explain the observed modulation of the electron and proton fluxes between 20 and 30 Jupiter radii on the basis of adiabatic theory and assumed symmetry with Jovigraphic longitude. Liouville's theorem is applied with the assumption that particles move conserving their magnetic moments. A magnetic model which matches the intensity and direction of the magnetic field along the Pioneer 10 trajectory is used for determining the positions of the equatorial crossings. Energetic electrons (1.3 MeV) compared in this way appear to be consistently described. Protons, on the other hand, show much weaker fluxes at the off-equatorial points than would be expected by this simple application of Liouville's theorem. Reasons for this discrepancy are offered.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Jan. 1
    Format: text
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  • 2
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    Anisotropies in the fluxes of Pioneer 10 protons (1979)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: One-hour-averaged fluxes of 1.8- to 2.15-MeV protons observed by the LET2 detector on Pioneer 10 on the inbound trajectory showed anisotropies attributable to corotation of Jupiter's magnetodisc only when Pioneer was near the dipole equator. Most of the time the anisotropy greatly exceeded the value expected from corotation. Gradients in the distribution function can be used to account for this excess anisotropy, but the amount of gradient required is unacceptably large by 1-2 orders of magnitude. If they were taken as real, these gradients would predict almost complete disappearance of these protons from Jupiter's magnetosphere in a matter of hours. The remedy is to introduce into the model of the distribution function proton flow along field lines away from the equator into both the southern and the northern hemisphere. The parallel flux at the southernmost latitudes reached by Pioneer can reach 25% of the product of proton density and velocity, i.e., 25% of the maximum possible.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Jan. 1
    Format: text
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  • 3
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    Low-velocity impact craters in ice and ice-saturated sand with implications for Martian crater count ages (1979)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The paper reports on a series of low-velocity impact experiments performed in ice and ice-saturated sand. It is found that crater diameters in ice-saturated sand were about 2 times larger than in the same energy and velocity range in competent blocks of granite, basalt and cement, while craters in ice were 3 times larger. It is shown that if this dependence of crater size on strength persists to large hypervelocity impact craters, then surface of geologic units composed of ice or ice-saturated soil would have greater crater count ages than rocky surfaces with identical influx histories. Among the conclusions are that Martian impact crater energy versus diameter scaling may also be a function of latitude.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 84; Dec. 30
    Format: text
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  • 4
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    Meteorite impact ejecta - Dependence of mass and energy lost on planetary escape velocity (1977)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: The amounts of material and energy which escape a planet in a meteorite impact event is calculated as functions of impact and escape velocities. Results are obtained from the computed flow induced by the impact of iron and gabbroic anorthosite spheres onto a half-space of anorthosite at impact velocities of 5 to 45 km/sec. The impact-induced flows were determined by a numerical method using the mass, momentum, and energy conservation relations in finite-difference approximation, within an Eulerian computational grid. The impact velocities at which ejecta losses equal meteorite mass gains are found to be approximately 20, 35, and 45 km/sec for anorthosite objects and approximately 25, 35, and 40 km/sec for iron objects striking anorthosite surfaces for the gravity fields of the moon, Mercury and Mars.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 198; Dec. 23
    Format: text
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  • 5
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    The Jovian electron spectrum and synchrotron radiation at 375 cm (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The synchrotron radiation expected at Earth from the region L=2.9-5 R sub J of Jupiter's magnetosphere is calculated using the Pioneer 10 electron model. The result is approximately 21 flux units (f.u.). This value is to be compared with 6.0 + or - 0.7 f.u., the flux density of synchrotron radiation measured from Jupiter's entire magnetosphere in ground-based radio observations. Most of the radiation at 375 cm is emitted by electrons in the 1 to 10 MeV range. If the electron model used for calculations is cut off below 10 MeV, the calculated flux is reduced to approximately 4 f.u., a level compatible with the radio observations.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-X-70876 , X-602-75-94
    Format: application/pdf
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  • 6
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    Compaction by impact of unconsolidated lunar fines (1975)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: New Hugoniot and release adiabat data for 1.8 g/cu cm lunar fines in the approximately 2 to 70 kbar range demonstrate that upon shock compression intrinsic crystal density (approximately 3.1 g/cu cm) is achieved under shock stress of 15 to 20 kbar. Release adiabat determinations indicate that measurable irreversible compaction occurs upon achieving shock pressures above approximately 4 kbar. For shocks in the approximately 7 to 15 kbar range, the inferred post-shock specific volumes observed decrease nearly linearly with increasing peak shock pressures. Upon shocking to approximately 15 kbar the post-shock density is approximately that of the intrinsic minerals. If the present data are taken to be representative of the response to impact of unconsolidated regolith material on the moon, it is inferred that the formation of appreciable quantities of soil breccia can be associated with the impact of meteoroids or ejecta at speeds as low as approximately 1 km/sec.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-142877 , CONTRIB-2626
    Format: application/pdf
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  • 7
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    Discrepancy in proton flux extrapolation along field lines in the middle Jovian magnetosphere (1978)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: Fluxes of energetic electrons and protons in Jupiter's outer magnetosphere were observed to be modulated with the 10 hour rotation period of the planet. This modulation was due to the concentration of particles at the magnetic equator: the non-alignment of Jupiter's spin and rotation axes caused Pioneer-10 to oscillate between +20 deg and -19 deg magnetic latitude and hence, between regions of stronger and weaker fluxes. The relationship between electron and proton fluxes observed off the magnetic equator was countered with measurements at the equatorial crossing radii of the same flux tubes by applying Liouville's theorem with the assumption that particles move conserving their magnetic moments. A magnetic model which matches the intensity and direction of the magnetic field along the Pioneer 10 trajectory was used for determining the positions of the equatorial crossings. Energetic electrons compared in this way appear to be consistently described. Protons, on the other hand, show much weaker fluxes at the off-equatorial points than would be predicted by this simple application of Liouville's theorem.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-79624
    Format: application/pdf
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  • 8
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    Absorption bands in the spectrum of Io (1978)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Near-infrared spectra of Io in the region from 2.8 to 4.2 microns are reported which show distinct absorption features, the most notable at 4.1 microns. Frozen volatiles or atmospheric gases cannot account for these absorptions, nor do they resemble those seen in common silicate rocks. Several candidate substances, most notably nitrate and carbonate salts, show absorption features in this spectral region; the deepest band in the spectrum may be a nitrate absorption. The satellite surface is shown to be anhydrous, as indicated by the absence of the 3-micron bound water band.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 225
    Format: text
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  • 9
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    The two faces of Iapetus (1975)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Radiometric and photometric observations of Iapetus are described, and a model is developed for the albedo distribution consistent with the visual light curves, color variations, and radiometric flux curve. The 20-micron infrared observations show that the radiometric variation differs by about 180 deg in phase from the visual light curve and has a peak-to-peak amplitude of about a factor of two, while the linear phase coefficient of the light curve varies, as the satellite rotates, from 0.028 to 0.068 mag/deg. Determination of the albedo distribution is described, and it is found to be characterized by a dark area covering most of the leading hemisphere, a bright trailing hemisphere, and a bright south polar cap. The radius is approximated as 800 to 850 km, and the mean geometric albedos for the light and dark faces are estimated as 0.35 and 0.07, respectively.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 24; Feb. 197
    Format: text
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  • 10
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    Planetary imaging - Past, present, and future (1976)
    In:  Other Sources
    Details
    Publication Date: 2019-06-27
    Description: Recent exploration of the planets has been highlighted by the development of visual imaging systems carried on board the spacecraft. This paper describes the evolution of planetary camera systems from the earliest reconnaissance flight to Mars in 1965 (Mariner 4) through the planned mission to Jupiter and Saturn in 1977. Advances in telecommunication performance, mission planning and operations, and digital processing of images are also discussed. Science objectives and changes in the imaging systems required to meet these objectives are discussed for the Mariner Mars 1971 (Mariner 9), Mariner Venus-Mercury (Mariner 10), Viking 1975 (Mars Orbiter), and Mariner Jupiter-Saturn 1977 missions. The last section of the paper describes future plans for imaging experiments based on cameras using solid-state sensors, particularly charge-coupled devices.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: IEEE Transactions on Geoscience Electronics; GE-14; July 197
    Format: text
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