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  • LUNAR AND PLANETARY EXPLORATION  (668)
  • 1980-1984  (668)
  • 1925-1929
  • 1980  (668)
  • 1
    Publication Date: 2018-06-02
    Description: A design concept for a ground based astrometric telescope that could significantly increase the potential accuracy of astrometric observations is considered. The state of current techniques and instrumentation is examined in the context of detecting extrasolar planets. Emphasis is placed on the direct detection of extrasolar planets at either visual or infrared wavelengths. The design concept of the imaging stellar interferometer (ISI), developed under Project Orion, is described. The Orion ISI employs the state-of-the-art technology and is theoretically capable of attaining 0.00010 arc sec/yr accuracy in relative astrometric observations.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-SP-436 , LC-80-11728
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  • 2
    Publication Date: 2013-08-31
    Description: New reflectance spectra of Ganymede, Europe, Callisto, Io, Saturn's rings, and Mars were obtained. The new data is combined with data covering other spectral regions for compositional interpretation. The spectral properties of water and mixtures of water plus other minerals were studied in the laboratory at the low temperatures typical of Mars, the Galilean satellites, and Saturn's rings. High precision reflectance spectra of water ice were studied.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-168732 , NAS 1.26:168732
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  • 3
    Publication Date: 2013-08-31
    Description: Voyager IRIS data reveal strong similarities among a broad range of features which differ considerably in visual appearance. The atmosphere above anticyclonic features, including the major white ovals, the Great Red Spot, and a zone, are cold relative to the immediate surroundings in the upper troposphere and tropopause region. These results are consistent with upwelling and divergence in this part of the atmosphere. A hot spot and a barge, which are localized cyclonic features, are found to be warm relative to their surroundings, implying subsidence with accompanying convergence. In all cases, the thermal wind shear associated with the features indicates a decay of the vorticity with height in the upper troposphere and lower stratosphere. Vertical velocities inferred from the observed temperature perturbations imply an upper limit of vertical mixing times near the tropopause of approximately 20 years. Temperatures in the upper stratosphere above the anticyclonic features show considerable variation, but in most cases are found to be relatively warm.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-80724
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  • 4
    Publication Date: 2013-08-31
    Description: Near infrared telescopic spectrophotometry for dark regions is present and interpreted using laboratory studies of iron bearing mineral mixtures and terrestrial oxidized and unoxidized basalts. Upon closer inspection (by spacecraft) the telescopic dark regions were found to consist of large scale intermixtures of bright soil (aeolian dust) and dark materials. The dark materials themselves consist of an intimate physical association of very fine grained ferric oxide bearing material with relatively high near infrared reflectance and darker, relatively unoxidized rocks or rock fragments. While these two components could exist finely intermixed in a soil, a number of lines of evidence indicate that the usual occurrence is probably a thin coating of physically bound oxidized material. The coated rocks are dark and generally clinopyroxene bearing. The shallow band depths and low overall reflectances indicate that opaque minerals such as magnetite are probably abundant.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-164072
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  • 5
    Publication Date: 2013-08-31
    Description: The contraction of the primitive protosaturnian cloud, using ideas of supersonic turbulent convection was modeled. The model suggested that each of Saturn's inner moons, excepting Rhea, condensed above the ice-point of water and consists primarily of hydrous magnesium silicates. The satellite mean densities steadily increase towards the planet and the rocky moons are irregular in shape.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-163630 , JPL-PUB-80-80
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  • 6
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    In:  CASI
    Publication Date: 2013-08-31
    Description: A 30 inch flat mirror was used with the solar telescope of the Kitt Peak National Observatory to obtain the integrated disc spectrum of the Sun between the wavelengths of 3000A and 4000A at a resolution of about two hundred thousand. The data obtained were used to calculate the intensities of the fluorescent lines of the OH radical in comets. The results were compared with those obtained using the center of the disc spectrum only. The wavelength of the reference point and the dispersion from which the wavelength of other points can be obtained are presented in tabular form.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-160005
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  • 7
    Publication Date: 2013-08-31
    Description: Temperatures and thermal winds, derived from Voyager infrared spectroscopy (IRIS) data over the Great Red Spot (GRS) and its environs, are presented. The atmosphere over the GRS is characterized by a tropopause which is cold relative to its environment and an upper stratosphere which is relatively warm. The cold tropopause implies a decrease in anticyclonic vorticity with height above 500 mb through the lower stratosphere. IRIS observations at 5 microns indicate little emission from the GRS itself, but enhanced emission in a ring about it, in agreement with recent ground based results. The behavior of the tropopause and 5 micron temperatures can be consistently interpreted as resulting from a circulation which rises within the GRS and subsides in the area around it. The explanation of the upper stratospheric temperatures is not so straightforward. A previous suggestion that they may be a manifestation of the linear vertical propagation of Rossby waves appears inconsistent with the gross east-west symmetry in the stratospheric temperatures over the GRS. The implications of the present results for various theoretical models of the GRS are examined, and the possibility that latent heat release drives the GRS is discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-80725
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  • 8
    Publication Date: 2013-08-31
    Description: Analyses of Voyager magnetic field measurements have extended the understanding of the structural and temporal characteristics of Jupiter's magnetic tail. The magnitude of the magnetic field in the lobes of the tail is found to decrease with Jovicentric distance approximately as r to he-1.4, compared with the power law exponent of -1.7 found for the rate of decrease along the Pioneer 10 outbound trajectory. Voyager observations of magnetic field component variations with Jovicentric distance in the tail do not support the uniform radial plasma outflow model derived from Pioneer data. Voyager 2 has shown that the azimuthal current sheet which surrounds Jupiter in the inner and middle magnetosphere extends tailward (in the anti-Sun direction) to a distance of at least 100 R sub J. In the tail this current sheet consists of a plasma sheet and embedded neutral sheet. In the region of the tail where the sheet is observed, the variation of the magnetic field as a result of the sheet structure and its 10 hr periodic motion is the dominant variation seen.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-80719
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  • 9
    Publication Date: 2013-08-31
    Description: Large scale (many minutes to 10 hours) magnetic field structures consisting predominantly of nearly north-south field direction were discovered in Jupiter's magnetosheath from the data of Voyagers 1 and 2 and Pioneer 10 during their outbound encounter trajectories. The Voyager 2 data, and that of Voyager 1 to a lesser extent, show evidence of a quasi-period of 10 hours (and occasionally 5 hours) for these structures. The north-south components of the field and plasma velocity were strongly correlated in the outbound magnetosheath as observed by Voyagers 1 and 2, and the components orthogonal to the north-south direction showed weak correlations. For both Voyager encounters the sense (positive and negative) of the north-south correlations were directly related to the direction of the ecliptic plane component of the interplanetary magnetic field using the field and plasma measurements of the non-encountering spacecraft.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-82035
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  • 10
    Publication Date: 2013-08-31
    Description: A detailed account is given of the energetic electron and proton populations as observed with Voyagers 1 and 2 during their passes through the dawn magnetotail of Jupiter. The region between 20 and 150 R sub J is dominated by a thin plasma sheet, where trapped energetic electron and proton fluxes reach their maximum. Proton spectra can be represented by an exponential in rigidity with a characteristic energy of approximately 50 keV. Proton anisotropies were consistent with corotation even at 100 R sub J. A major proton acceleration event as well as several cases of field aligned proton streaming were observed. The flux of 0.4 MeV protons decreases by three orders of magnitude between 30 and 90 R sub J and then remains relatively constant to the magnetopause. Fine structure in the data indicate longitudinal asymmetries with respect to the dipole orientation. Electron spectra in the magnetosheath and interplanetary space are modulated by the Jovian longitude relative to the subsolar point.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-81991
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  • 11
    Publication Date: 2013-08-31
    Description: A model is presented that can account for several features of the dynamic spectral arcs observed at decameter wavelengths by the planetary radio astronomy experiment on Voyagers 1 and 2. It is shown that refraction of an extraordinary mode wave initially excited nearly orthogonal to the local magnetic field is significantly influenced by the local plasma density, being greater the higher the density. It is assumed that the source of the decameter radiation lies along the L = 6 flux tube and that the highest frequencies are produced at the lowest altitudes, where both the plasma density and magnetic field gradients are largest. It is further assumed that the decameter radiation is emitted into a thin conical sheet, consistent with both observation and theory. In the model the emission cone angle of the sheet is chosen to vary with frequency so that it is relatively small at both high and low frequencies, but approximately 80 deg at intermediate frequencies. The resulting emission pattern as seen by a distant observer is shown to resemble the observed arc pattern. The model is compared and contrasted with examples of Voyager radio data.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-81987
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  • 12
    Publication Date: 2013-08-31
    Description: Fine scale magnetic field data from the Voyager 1 and 2 magnetopause and bow shock crossings at Jupiter were analyzed. Explicit models of the dawnside magnetopause and bow shock in Jupiter's orbital plane employ an axisymmetric parabola and hyperbola, respectively, and are determined separately for the encounters. A new phenomenon was discovered in the magnetosheath. It is manifested as (5 or) 10 hour quasi-periodic modulation of the direction of the magnetic field in the outbound magnetosheath, predominantly in the northward (N) and southward (S) directions. It was seen to occur during both encounters and appears most evident in Voyager 2 outbound observations, probably due to the extreme tailward extent of the Voyager 2 trajectory through the magnetosheath. The durations of the N to and from S transitions range from tens of minutes to approximately 3 hours. The directional variation of the field during these transitions is fairly well restricted to a plane parallel to the local model magnetopause location. These signatures may be due to magnetosheath field line draping modulated by the large scale motion of the magnetospheric plasma disk.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-82033
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  • 13
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    In:  CASI
    Publication Date: 2013-08-31
    Description: Among warm giant stars, rapid mass loss sets in along a well defined velocity dividing line (VDL). Hot corona also disappear close to the VDL and thermal pressure cannot drive the observed rapid mass loss in these stars. The VDL may be associated with magnetic fields changing from closed to open. Such a change is consistent with the lack of X-rays from late-type giants. A magnetic transition locus based on Pneuman's work on helmet streamer stability agrees well with the empirical VDL. The change from closed to open fields not only makes rapid mass loss possible, but also contributes to energizing the mass loss in the form of discrete bubbles.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-163602 , BA-80-31
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  • 14
    Publication Date: 2013-08-31
    Description: The mosaics and derivative products produced from many individual high resolution images acquired by the Viking Lander Camera Systems are described: A morning and afternoon mosaic for both cameras at the Lander 1 Chryse Planitia site, and a morning, noon, and afternoon camera pair at Utopia Planitia, the Lander 11 site. The derived products include special geometric projections of the mosaic data sets, polar stereographic (donut), stereoscopic, and orthographic. Contour maps and vertical profiles of the topography were overlaid on the mosaics from which they were derived. Sets of stereo pairs were extracted and enlarged from stereoscopic projections of the mosaics.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-3326
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  • 15
    Publication Date: 2013-08-31
    Description: The extremely long missions of the two Viking Orbiter spacecraft produced a wealth of photos of surface features. Many of which can be used to form stereo images allowing the earth-bound student of Mars to examine the subject in 3-D. This catalog is a technical guide to the use of stereo coverage within the complex Viking imaging data set. Since that data set is still growing (January, 1980, about 3 1/2 years after the mission began), a second edition of this catalog is planned with completion expected about November, 1980.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-3277
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  • 16
    Publication Date: 2013-08-31
    Description: The question of whether the crater population on Phobos represents a production population or an equilibrium population is considered. The absolute ages of cratered surfaces are interpreted and analyzed. A computer program was developed to study the dynamics of material ejected from Martian satellites and to investigate the hypothesis that at least some of the extensive set of linear features discovered on the surface of Phobos could be the result of secondary cratering from the Stickney impact. The possibility that Deimos was catastrophically disrupted by a large impact but subsequently reaccreted is considered as well as the probability the Phobos had an impact nearly large enough to disrupt it are also discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-163005
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  • 17
    Publication Date: 2013-08-31
    Description: Available data on imaging, infrared spectroscopy and radiometry, triaxial fluxgate magnetometers, the multifilter photopolarimeter, planetary radio astronomy, and radio science is described. The Voyager experiments are listed, and it is indicated on which experiments data is available.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-84017 , NSSDC/WDC-A-R/S-80-13
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  • 18
    Publication Date: 2013-08-31
    Description: The enigmatic control of the occurrence frequency of Jupiter's decametric emissions by the satellite Io is explained theoretically on the basis of its strong electrodynamic interaction with the corotating Jovian magnetosphere leading to field aligned currents connecting Io with the Jovian ionosphere. Direct measurements of the perturbation magnetic fields due to this current system were obtained by the magnetic field experiment on Voyager 1 on 5 March 1979 when it passed within 20,500 km south of Io. An interpretation in the framework of Alfven waves radiated by Io leads to current estimates of 2.8 million amps. A mass density of 7400 to 13600 proton mass units per Cu cm is derived which compares very favorably with independent observations of the torus composition characterized by 7-9 proton mass units per electron for a local electron density of 1050 to 1500 per cu cm. The power dissipated in the current system may be important for heating the Io heavy ion torus, inner magnetosphere, Jovian ionosphere, and possibly the ionosphere or even the interior of Io.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-82060
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  • 19
    Publication Date: 2013-08-31
    Description: Broadband S-20, B and V magnitudes of P/Encke were obtained with the digital area photometer, using an Image Dissector Scanner (IDS) detector on the 2.7 m telescope at McDonald Observatory during August 1979. The notation V(S-20) is used for S-20 magnitudes transformed to V magnitudes. The variation in the V(S20) magnitudes (26, 5 minute integrations) on the best photometric night (21 August) was small and random indicating either a lack of rotational albedo variations or, more likely, a masking of the nucleus by the outburst activity. A spectrum covering the region from 3630 to 4900 A at a resolution of 5 A was obtained on 27 August with the IDS spectrograph. The spectrum was featureless, showing no emission at the CN or CO+ wavelengths.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: REPT-1 , NASA-CR-163717
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  • 20
    Publication Date: 2013-08-31
    Description: The effective level of line formation for spectroscopic absorption lines has long been regarded as a useful parameter for determining average atmospheric values of the quantities involved in line formation. The identity of this parameter was recently disputed. The dependence of this parameter on the average depth where photons are absorbed in a semi-infinite atmosphere is established. It is shown that the mean depths derived by others are similar in nature and behavior.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-163617
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  • 21
    Publication Date: 2013-08-31
    Description: The coordinate systems of each of the Galilean satellites are defined and coordinates of features seen in the Voyager pictures of these satellites are presented. The control nets of the satellites were computed by means of single block analytical triangulations. The normal equations were solved by the conjugate iterative method which is convenient and which converges rapidly as the initial estimates of the parameters are very good.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: RAND/P-6479 , NASA-CR-163582
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  • 22
    Publication Date: 2013-08-31
    Description: A terrain modeling algorithm that would reconstruct the sensed ground images formed by the triangulation scheme, and classify as unsafe any terrain feature that would pose a hazard to a roving vehicle is described. This modeler greatly reduces quantization errors inherent in a laser/sensing system through the use of a thinning algorithm. Dual filters are employed to separate terrain steps from the general landscape, simplifying the analysis of terrain features. A crosspath analysis is utilized to detect and avoid obstacles that would adversely affect the roll of the vehicle. Computer simulations of the rover on various terrains examine the performance of the modeler.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-163492 , RPI-TR-MP-75
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  • 23
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    In:  CASI
    Publication Date: 2013-08-31
    Description: A historical investigation reveals that Newcomb omitted to complete the calculation for the mass of mercury which would have given 8,405,291(-1), but instead arbitrarily adopted a value of 6,000,000(-1). This baseless figure 6000000(-1) became generally accepted and adopted in subsequent attempts to improve the mass. That only small changes have emerged is likely to be no more than a consequence of relying on a least squares process. Reduction of the Mercury mass to 9,000,000(-1) would alter theoretical angular positions of Venus by less than inherent observational errors, but the theoretical distances would be changed by amounts probably capable of detection by radar means.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-163438 , JPL-PUB-80-44
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  • 24
    Publication Date: 2013-08-31
    Description: The mechanism of magnetic pumping consists of two processes, the adiabatic motion of charged particles in a time varying magnetic field and their pitch-angle diffusion. The result is a systematic increase in the energy of charged particles trapped in mirror (and particularly, magnetospheric) magnetic fields. A numerical model of the mechanism is constructed, compared with analytic theory where possible, and, through elementary exercises, is used to predict the consequences of the process for cases that are not tractable by analytical means. For energy dependent pitch angle diffusion rates, characteristic 'two temperature' distributions are produced. Application of the model to the outer Jovian magnetosphere shows that beyond 20 Jupiter radii in the outer magnetosphere, particles may be magnetically pumped to energies of the order of 1 - 2 MeV. Two temperature distribution functions with "break points" at 1 - 4 KeV for electrons and 8 - 35 KeV for ions are predicted.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-163022 , REPT-80-5
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  • 25
    Publication Date: 2013-08-31
    Description: Observations of Jupiter's low frequency radio emissions collected over one month intervals before and after each Voyager encounter were analyzed. Compilations of occurrence probability, average power flux density and average sense of circular polarization are presented as a function of central meridian longitude, phase of Io, and frequency. The results are compared with ground based observations. The necessary geometrical conditions are preferred polarization sense for Io-related decametric emission observed by Voyager from above both the dayside and nightside hemispheres are found to be essentially the same as are observed in Earth based studies. On the other hand, there is a clear local time dependence in the Io-independent decametric emission. Io appears to have an influence on average flux density of the emission down to below 2 MHz. The average power flux density spectrum of Jupiter's emission has a broad peak near 9MHz. Integration of the average spectrum over all frequencies gives a total radiated power for an isotropic source of 4 x 10 to the 11th power W.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-TM-80717
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  • 26
    Publication Date: 2013-08-31
    Description: The measurement of longitude of the Viking 1 landing site and the accuracy of the coordinates of features in the area around the landing site are discussed. The longitude must be measured photogrammatically from the small crater, Airy 0, which defines the 0 deg meridian on Mars. The computer program, GIANT, which was used to perform the analytical triangulations, and the photogrammetric computation of the longitude of the Viking 1 lander site are described. Improved coordinates of features in the vicinity of the Viking 1 lander site are presented.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: RAND/R-2600-NASA , NASA-CR-153193
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  • 27
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    In:  CASI
    Publication Date: 2013-08-31
    Description: The travel times of the seismic waves obtained for the Apollo-14 and -16 active seismic experiments and the Apollo-16 grenade launches are shown to be consistent with a powder-layer model of the shallow lunar crust. The velocity variation with depth determined from these data is: V(z) = approximately 110 z to the 1/6 power m/sec for z less than 10 meters and V(z) is nearly = to 250 m/sec for z greater than 10 meters. The velocity values found for the 10 meter depth are similar to those found by Kovach, et al. (1972). The z to the 1/6 power depth dependence for the velocity of the topmost layer is that predicted on the basis of a powder layer (Gangi, 1972). The Amplitude variation of the direct waves as a function of source-to-receiver separation, x, is A(x) = A(o)x to the -n power exp(-ax) where 1.5 n 2.2 and a is nearly = to 0.047 neper/m. Velocity-spectra analyses of the direct, surface-reflected, bottom-reflected and refracted waves give results that are consistent with the velocity model inferred from the traveltime data.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-162573
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  • 28
    Publication Date: 2016-03-09
    Description: Various vehicle and mission options were investigated for the continued exploration of Mars; the cost of a minimum sample return mission was estimated; options and concepts were synthesized into program possibilities; and recommendations for the next Mars mission were made to the Planetary Program office. Specific sites and all relevant spacecraft and ground-based data were studied in order to determine: (1) the adequacy of presently available data for identifying landing sities for a sample return mission that would assure the acquisition of material from the most important geologic provinces of Mars; (2) the degree of surface mobility required to assure sample acquisition for these sites; (3) techniques to be used in the selection and drilling of rock a samples; and (4) the degree of mobility required at the two Viking sites to acquire these samples.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: JPL-PUB-80-59 , NASA-CR-164558
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  • 29
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    In:  CASI
    Publication Date: 2016-06-07
    Description: The Deep Space Network report on tracking and data acquisition for Voyager Project is continued. The period of August through October 1980 is covered. The use of beacons for interplanetary navigation, specifically for target related navigation, was shown to be of significant value.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: The Telecommun. and Data Acquisition; p 44-59
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  • 30
    Publication Date: 2016-06-07
    Description: The data acquisition and processing technqiues used in the Pioneer Venus differential long baseline interferometry experiment are discribed. The experiment was designed to measure the motion in three dimensions of the Pioneer probes during their fall to the surface of Venus, using a combination of Doppler and long baseline ratio interferometric methods. The design of the experiment and the equipment and software techniques that were developed specially for this experiment are also described.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: The Telecommun. and Data Acquisition Rept.; p 140-149
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  • 31
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    In:  CASI
    Publication Date: 2016-03-09
    Description: The physical, chemical, thermodynamic, and geologic data on lunar rocks, minerals, and processes are summarized, and a set of data metals that might be extracted from lunar materials is presented.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-RP-1057
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  • 32
    Publication Date: 2016-06-07
    Description: A brief history of the Viking Missions is presented. The status of the present Viking Orbiter and Landers for the period from February 1, 1980 through March 31, 1980 is discussed, with emphasis on data transmission abilities.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: The Telecommun. and Data Acquisition Rept.; p 58-61
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  • 33
    Publication Date: 2017-10-02
    Description: The solar wind plasma analyzer on board Pioneer 2 provides first observations of low-energy positive ions in the magnetosphere of Saturn. Measurable intensities of ions within the energy-per-unit charge (E/Q) range 100 eV to 8 keV are present over the planetocentric radial distance range about 4 to 16 R sub S in the dayside magnetosphere. The plasmas are found to be rigidly corotating with the planet out to distances of at least 10 R sub S. At radial distances beyond 10 R sub S, the bulk flows appear to be in the corotation direction but with lesser speeds than those expected from rigid corotation. At radial distances beyond the orbit of Rhea at 8.8 R sub S, the dominant ions are most likely protons and the corresponding typical densities and temperatures are 0.5/cu cm and 1,000,000 K, respectively, with substantial fluctuations. It is concluded that the most likely source of these plasmas in the photodissociation of water frost on the surface of the ring material with subsequent ionization of the products and radially outward diffusion. The presence of this plasma torus is expected to have a large influence on the dynamics of Saturn's magnetosphere since the pressure ratio beta of these plasmas approaches unity at radial distances as close to the planet as 6.5 R sub S. On the basis of these observational evidences it is anticipated that quasi-periodic outward flows of plasma, accompanied with a reconfiguration of the magnetosphere beyond about 6.5 R sub S, will occur in the local night sector in order to relieve the plasma pressure from accretion of plasma from the rings.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: AD-A096079 , U-OF-IOWA-80-12
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  • 34
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    In:  CASI
    Publication Date: 2017-10-02
    Description: The extended atmosphere of the Jupiter system consists of atoms and ions of heavy elements. This material originates on the satellite Io. Energy is lost from the thermal plasma in collisionally excited optical and ultraviolet emission. The juxtaposition of Earth and spacecraft measurements provide insight concerning the underlying processes of particle transport and energy supply.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NASA-CR-163603
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  • 35
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    In:  Other Sources
    Publication Date: 2011-08-18
    Description: A survey of Brazilian meteorites is presented, along with basic premises of meteoritics, including classification, naming, and analytic procedures. Meteorites are noted to be of interest as representative samples of ancient rocks, perhaps half as old as the universe, as sometimes originating from outside the solar system, containing early solar material, and containing evidence of cosmic ray interactions or collisions. The characteristics which make up the achondrite and chondrite group are reviewed, and a listing of the primary characteristics of known Brazilian meteorites is provided.
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  • 36
    Publication Date: 2011-08-18
    Description: During the formation of the solar system the variation of the gravitational field produced by removal of a nebula with its moderately massive accretion disk led to sweeping of the Jovian commensurability resonances through the asteroid zone. This process produced increased eccentricities and random velocities of the early planetesimals which resulted in collisional comminution rather than accretion. The existence of the asteroids, their low mass density, and their high relative velocities are interpreted as due to disruption of the accretion processes of the terrestrial planets by the influences of Jupiter.
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    Type: Icarus; 44; Dec. 198
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  • 37
    Publication Date: 2011-08-18
    Description: Three representative numerical simulations of the growth of the terrestrial planets by accretion of large protoplanets are considered. The mass and relative-velocity distributions of the bodies are free to evolve simultaneously in response to close gravitational encounters and occasional collisions between bodies. The collisions between bodies arise therefore in a natural way and the assumption of expressions for the relative-velocity distribution and the gravitational collision cross section is unnecessary. These simulations indicate that the growth of bodies with final masses approaching those of Venus and earth is possible, at least for the case of a two-dimensional system
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 44; Dec. 198
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  • 38
    Publication Date: 2011-08-18
    Description: VJHK measurements of J6 Himalia and S9 Phoebe, using the new NASA IRTF telescope, show that these objects have carbonaceous chondritic type colors in the 0.5- to 2.2-micron region. For Phoebe, this is in contrast to the JHK colors published by Cruikshank (1980), which indicated that the satellite's surface was unlike the material found on asteroids and on the dark side of Iapetus. J6 is known to have a low albedo from thermal infrared studies (Cruikshank, 1977), and the new VJHK observations of S9 imply that it also has a low albedo. The H and K reflectances of S9 are slightly lower than those of J6, suggesting some slight difference in surface composition or a contamination by foreign material. The conjectured low albedo of S9 can be tested with measurements in the thermal infrared.
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  • 39
    Publication Date: 2011-08-18
    Description: The ionospheric plasma density on magnetic field lines threading the Jovian rings which are located inside approximately 1.8 Jupiter radii on the jovigraphic equatorial plane is calculated by using a rotating ion exosphere model. It is found that the bulk of the ionospheric particles on these field lines are on ballistic trajectories. On field lines approximately symmetric with respect to the jovigraphic equator, the ring, which to a first approximation would absorb the population of trapped particles, consequently has little effect. On field lines which are made asymmetric by the higher-order multipoles of Jupiter's field and the tilt of the dipole axis, the rings may have a significant effect. It is suggested that better definition of the rings' atmospheric and ionospheric properties is required to model these localized effects. If the rings are found to be an important plasma source for the inner magnetosphere, the present exospheric model will have to be revised.
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  • 40
    Publication Date: 2011-08-18
    Description: Monitoring of Io's neutral sodium emission cloud, monitored from two earth observatories during the period of the Voyager 1 encounter, demonstrated that the behavior of the cloud is complex; displaying a variety of changes, both systematic and secular, which can have both time and spatial dependencies while also possessing some characteristics of stability. Dynamic models of the sodium cloud employing Voyager 1 plasma data provide a reasonable fit to the encounter images of one of the observatories. The modeling assumptions of anisotropic ejection of neutral sodium atoms from the leading, inner hemisphere of Io, with a velocity distribution characteristic of sputtering, adequately explain the overall intensity distribution of the 'near cloud'.
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  • 41
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    Publication Date: 2011-08-18
    Description: The mechanical properties of elemental sulfur are such that the upper crust of Io cannot be primarily sulfur. For heat flows in the range 100-1000 ergs/sq cm sec sulfur becomes ductile within several hundred meters of the surface and would prevent the formation of calderas with depths greater than this. However, the one caldera for which precise depth data are available is 2 km deep, and this value may be typical. A study of the mechanical equilibrium of simple slopes shows that the depth to the zone of rapid ductile flow strongly controls the maximum heights for sulfur slopes. Sulfur scarps with heights greater than 1 km will fail for all heat flows greater than 180 ergs/sq cm sec and slope angles greater than 22.5 deg. The observed relief on Io is inconsistent with that anticipated for a predominantly sulfur crust. However, a silicate crust with several percent sulfur included satisfies both the mechanical constraints and the observed presence of sulfur on Io.
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  • 42
    Publication Date: 2011-08-18
    Description: Assuming that the micron-sized particles making up the bright Jovian ring are fragments of erosive collisions between micrometeoroid projectiles and large parent bodies, a physical model of the ring is calculated. This leads to a well-defined size distribution for the ejecta, whose optical properties can be compared with observation. The (most likely silicate) ejecta material maximum diameter is estimated to be 0.1 micron, and most likely the result of Io volcanic activity. The impact model's determination of ejecta size distribution in turn determines the structure of the ring, with the largest ejecta forming the bright ring, medium-sized ejecta forming a disk that extends to the Jovian atmosphere, and small ejecta forming a faint halo whose structure is dominated by electromagnetic forces.
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  • 43
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    Publication Date: 2011-08-18
    Description: Significant near-surface flow of gas several hundred kilometers from Pele (Plume 1) on Io is indicated by a series of bright, elongate albedo markings. Particles produced at small, local vents are apparently carried as much as 70 km farther 'downwind' from Pele. The gas densities and velocities necessary to suspend 0.1 to 10 micron particles at such a distance imply mass flow rates of 10 to the 7th - 10 to the 9th g/sec. Such flow rates are consistent with other estimates of mass transport by the plume. The large flow rates so far from the source allow an estimate of the rate of resurfacing of Io by lava flows and pyroclastics that is independent of estimates based on meteorite flux or on the amount of solids carried within the plumes themselves.
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  • 44
    Publication Date: 2011-08-18
    Description: Infrared observations of the Io eclipse of April 12, 1980, in five broad bands from 3 to 30 microns define the thermal emission spectrum both during and after eclipse. A substantial fraction of the emitted radiation during eclipse arises from hot spots; the equivalent global average heat flow is 1.5 + or - 0.3 W/sq m, corresponding to an internal source of (6 + or - 1) x 10 to the 13th W. The hot spot spectra can be matched by components with color temperatures of 200-600 K covering 1-2% of the surface. Comparison with observations over the past eight years suggests that, while the flux at the hottest temperatures may be highly variable, there is no evidence for major changes in the total heat flow, which is emitted primarily in the spectral region 10-20 microns. The heating curves of the surface were observed at 10 and 20 microns; when corrected for the hot spot contribution they indicate a typical global thermal inertia for Io of 0.0002 + or - 0.0001 cal/sq cm sec(exp 1/2) K, similar to that of the other Galilean satellites.
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  • 45
    Publication Date: 2011-08-18
    Description: Among the topics covered by the colloquium on the satellites of Jupiter are: the internal energy and thermophysics of the surface of Io, plume volcanism on Io, the photometric variability of Io, the near-surface flow of volcanic gases on Io, and the sodium emission cloud of Io and its north-south asymmetry. Also considered are: the physical processes and origins of Jupiter's ring and its possible effect on the Jovian inner plasmasphere, the composition of such moons of Jupiter as Amalthea, Ganymede, Europa and Callisto and their lithospheric and ice evolutions. Particular attention is given such topographic features as the domes and grooved terrain on Ganymede, water frost and ice, and the photometric properties of these outer satellites of Jupiter.
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  • 46
    Publication Date: 2011-08-18
    Description: Doppler radio tracking of the Pioneer Venus orbiter has provided gravity measures over a significant portion of Venus. Feature resolution is approximately 300-1000 km within an area extending from 10 deg S to 40 deg N latitude and from 70 deg W to 130 deg E longitude (approximately equal to 200 deg). Many anomalies were detected, and there is considerable correlation with radar altimetry topography (Pettengill et al., 1980). The amplitudes of the anomalies are relatively mild and similar to those on earth at this resolution. Calculations for isostatic adjustment reveal that significant compensation has occurred.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 198
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  • 47
    Publication Date: 2011-08-18
    Description: A topographic map of 93% of the Venus globe was depicted by the radar altimeter of the Pioneer Venus orbiter with a resolution better than 150 km. Extremes in relief expressed as a center-of-mass-to-surface radius extend from 6049 to 6062 km; the elevated terrain is dominated by a massive equatorial area equal in size to South America. The distribution of average meter-scale surface slopes is determined for the same regions in the 1 to 10 deg range; elevated areas have higher slopes, so that most features observed in the earth-based images are also evident in the vertical-incidence spacecraft measurements.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 48
    Publication Date: 2011-08-18
    Description: Aerodynamic testing of the Pioneer Venus small probe net flux radiometer (SNFR) has led to a better understanding of transient errors in the net flux measurements immediately following deployment. Corrections to the net flux profiles in this region produce profiles that are reasonably consistent with constraints imposed by ground-based and orbiter results for fluxes above the atmosphere. The tests raised questions about possible steady state errors associated with the changing atmospheric temperature encountered as the probes descended. However, the lack of sensor-to-sensor variability of the transient error (caused by a newly discovered flow-through mechanism) suggests that any related errors discovered by future testing will be correctable and will not alter the conclusions that net fluxes in the lower atmosphere vary considerably with location and are relatively large at the north and night probe sites.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 49
    Publication Date: 2011-08-18
    Description: The UV measurements of the Venus atmosphere absorbers constrain the location, altitude, and identity near the Venus cloud tops. The spin-scan images observed by the Pioneer Venus orbiter spectrometer (UVS) and the cloud photopolarimeter measure contrasts in the 1990-3650 A range and at phase angles between 33 and 130 deg; the planet is darkest at the location where the UVS line of sight penetrates in the direction perpendicular to the cloud tops. SO2 absorption accounts for the contrast from 2000 to 3200 A; the persistence of contrast at longer wavelengths requires another absorber at about 75-mbar altitude. The correlation between the planetary differences and polarization does not need large-scale clearing or major vertical motions of the cloud tops as the main cause of the observed variations.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 50
    Publication Date: 2011-08-18
    Description: The horizontal and vertical cloud structures, atmospheric waves, and wind velocities at the cloud top level were determined by the Pioneer Venus photopolarimeter images in the UV from January through March 1979. The images indicate long-term evolution of cloud characteristics, the atmospheric dynamics, and rapid small changes in cloud morphology. The clouds show a globally coordinated oscillation relative to latitude circles; retrograde zonal winds of 100 m/s near the equator are determined from the tracking of small-scale cloud properties, but two hemispheres show important variations. The zonal wind velocity in the southern hemisphere is reduced toward the poles at a rate similar to solid body rotation; the midlatitude jet stream noted by Mariner 10 is not observed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 51
    Publication Date: 2011-08-18
    Description: The results presented represent a synthesis of data from those Pioneer Venus experiments directed toward studying cloud problems. These orbiter and multiprobe experiments show the cloud system to consist of three altitude regions populated by cloud particles and smaller haze particles which extend above and below as well as coexist with the cloud particles. The optical properties derived are only consistent with the largest particles, having platelike morphology. The smallest particles are shown to require changes in chemical composition to explain observed behavior. The medium-sized H2SO4 droplets of 2 micrometers diameter appear to be the least volatile and are the best understood. The role of the cloud particles in precipitation dynamical processes, lightning, and radiation are all discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 52
    Publication Date: 2011-08-18
    Description: The Pioneer Venus data relevant to the dynamics and thermodynamics of the atmosphere is summarized and interpreted. On the day side there is a thermosphere in which temperatures increase with height to an exospheric temperature of about 300 K. On the night side there is a cryosphere in which temperatures decrease with height to an exospheric temperature of about 100 K. The atmosphere is stratified stably from the highest altitudes down to about 28 km except for a layer in the clouds between about 50 and 55 km which is nearly adiabatic. Horizontal thermal contrasts are approximately 1 to 2% in the deep atmosphere and 100% in the upper atmosphere. The temperatures generally decrease with latitude at and below the clouds on constant pressure surfaces. Above the clouds there is a reversed zonally averaged latitudinal temperature gradient. The dominant circulation of the atmosphere above the lowest one or two scale heights is a zonal retrograde motion with 100 m/s winds at 60 km altitude. There is also a superrotation at altitudes of 150 km and above.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: NAGW-47 , Journal of Geophysical Research; 85; Dec. 30
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  • 53
    Publication Date: 2011-08-18
    Description: Atmospheric densities of Venus were measured from the orbital decay of the Pioneer Venus from Dec. 9, 1978 to Aug. 7, 1979 near the 16 deg latitude between 140 and 190 km during the entire day. Comparative atmospheric densities on earth at 150 km are higher by a factor of 3.5 with only a 1% diurnal variation; an atmospheric composition, temperature, and density model based on the orbiter atmospheric drag (OAD) vertical structure is presented. The model shows that atomic oxygen is the major component in the Venus atmosphere above 145 km at night and above 160 km during the day with mixing ratios over 0.1 near 140 km; drag measurements indicate O concentrations from 1 x 10 to the 9th/cu cm in daytime to 3 x 10 to the 7th/cu cm at night. It is concluded that the neutral upper atmosphere of Venus is surprisingly insensitive to solar extreme UV variations and changes in the solar wind.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 54
    Publication Date: 2011-08-18
    Description: The thermal structure of the Venus atmosphere and differences in structure with latitude (up to 60 deg) and clock hour (from midnight to 8 AM) have been measured in situ from a height of 126 km to the surface by instruments on the four Pioneer Venus entry probes. It is found that thermal contrasts below 45 km are a few K, with the midlatitudes warmer than both equatorial and high latitudes. Considerable temperature and pressure differences with latitude develop in the clouds (25 K and 20 mbar level). In addition, upward of 110 km, there is evidence of large-amplitude temperature oscillations with altitude, believed to signify the presence of large-amplitude waves, perhaps thermal tides. Agreement of structure data from other Pioneer Venus experiments is generally excellent.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 55
    Publication Date: 2011-08-18
    Description: The in-situ measurements of the global composition and Venus ionosphere dynamics recorded by the Bennett ion mass spectrometer on the Pioneer Venus orbiter during Dec. 1978-Aug. 1979 are presented. The observations of three plasma regimes show the bowshock-ionosheath region, the thermal ionosphere, and a superthermal flowing ion layer contacting the ionosphere at the ionopause and extending outward to different heights above the planet. An abundant ionosphere dominated by O(+) above 200 km and by O2(+) down to the typical periapsis altitudes of 160 km occur during quiet periods; less disturbed data shows strong day to night changes in the distributions of ions including O(+), O2(+), CO2(+), and N(+). The ionopause is located near the subpolar point at 250-400 km; under disturbed nighttime conditions it may have randomly spaced concentration gradients in the dusk region.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 56
    Publication Date: 2011-08-18
    Description: The portion of solar wind interacting with the dayside ionosphere and atmosphere of Venus was determined based on magnetic field fluctuations in the ionosheath and the interaction with the upper neutral atmosphere above the ionopause. Fluctuations with the ratio of the number of particles intersecting the daytide ionopause to the total number of particles of 0.3 suggest that about 0.3% of solar wind may be absorbed. Most of fast H atoms resulting from the charge exchange interactions with the atmosphere escape; some of the energy deposition processes produce observable signatures (such as a narrow Lyman alpha emission region), but penetrating solar wind particles do not control the physical and/or chemical structure of the daytime Venus ionosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 57
    Publication Date: 2011-08-18
    Description: The paper investigates the Kelvin-Helmholtz instability at the Venus ionopause resulting from the flow of the (shocked) solar wind tangential to the ionopause for the case where the interplanetary field is oriented normal to the direction of flow. It is found that gravity stabilizes the long wavelength perturbations, and the finite thickness of the boundary layer stabilizes short wavelength modes. The magnetic 'gyroviscosity' due to finite Larmor radius effects either destabilizes the boundary or stabilizes it according to whether the solar wind electric field points away from or toward the ionosphere. For solar wind and ionosphere plasma parameters consistent with Pioneer Venus observations, it is found that the instabilities with the greatest growth rates (shortest growth times) have wavelengths of 50-150 km and growth times of 0.5 to several seconds. In addition, it is found how distortion of the ionopause by Kelvin-Helmholtz instability might lead to the formation of magnetic 'flux ropes' inside the ionosphere as well as ionospheric 'bubbles' embedded in the solar wind.
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    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 58
    Publication Date: 2011-08-18
    Description: For three orbit paths of the Pioneer Venus orbiter the interaction between the solar wind and the Venusian ionosphere has been studied. Results of the retarding potential analyzer and the magnetometer are described for the boundary region between the solar wind and the planetary ionosphere. These are the first measurements that show that a transition region exists between the two plasmas of different origin. The observed magnetic field and current system producing it appear strong enough to stop the solar wind flow in front of the ionosphere and to separate the shocked solar wind from the ionosphere. The transition region between the ionosheath and the ionosphere is called the 'mantle'. The observed mantle electron energy spectra close to the ionopause show ionospheric character. With increasing height the number of electrons that have ionospheric energies decreases, and the number of electrons that have solar wind energies gradually increases toward the ionosheath boundary, where only solar wind energy spectra are observed. The mantle surrounds the frontside of the ionosphere and extends probably more than eight Venus radii downstream.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 59
    Publication Date: 2011-08-18
    Description: The Pioneer Venus plasma wave instrument is described with a discussion of wave observations throughout the typical near-noon and near-midnight orbits. This is followed by a comparison of the bow shock turbulence characteristics at earth and at Venus. The wave-particle interactions detected near the dayside ionopause are analyzed showing that the whistler mode Landau damping develops when the B field direction changes so that the whistler becomes oblique.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 30
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  • 60
    Publication Date: 2011-08-18
    Description: Aerosol profiles of the Jovian stratosphere and troposphere are presented using the Galilean satellite eclipse technique. The aerosol content is tenuous and varies with altitude, increasing rapidly with downward passage through the tropopause. The data indicate the presence of some aerosols of undetermined structure above the tropopause. An extended haze distribution is proposed, but the possibility that the stratospheric aerosol resides in a thin layer is not excluded.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 44; Oct. 198
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  • 61
    Publication Date: 2011-08-18
    Description: Analytical and numerical models of plasma temperatures in the Venusian ionosphere are proposed. The magnitudes of plasma thermal parameters are calculated using thermal-structure data obtained by the Pioneer Venus Orbiter. The simple models are found to be in good agreement with the more detailed models of thermal balance. Daytime and nighttime temperature data along with corresponding temperature profiles are provided.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 44; Oct. 198
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  • 62
    Publication Date: 2011-08-18
    Description: The possible synthesis of organic molecules by the absorption of galactic cosmic rays in an N2-CH4-H2 Titan model atmosphere has been studied. The cosmic-ray-induced ionization results in peak electron densities of 2000/cu cm, with NH(+), C3H9(+), and C4H9(+) being among the important positive ions. Details of the ion and neutral chemistry relevant to the production of organic molecules are discussed. The potential importance of N(2D) reactions with CH4 and H2 is also demonstrated. Although the integrated production rate of organic matter due to the absorption of the cosmic ray cascade is much less than that by solar ultraviolet radiation, the production of nitrogen-bearing organic molecules by cosmic rays may be greater.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 44; Oct. 198
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  • 63
    Publication Date: 2011-08-18
    Description: A model of Pluto's interior is presented based on new estimates of its mass within the range of possible masses. The model is consistent with the most recent observations by Arnold et al., and calls for a silicate-poor, H2O ice-rock bulk composition of Pluto. The results of the Charon-Pluto eclipses will lead to a more conclusive constraint to Pluto's bulk composition.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 44; Oct. 198
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  • 64
    Publication Date: 2011-08-18
    Description: The methane abundance in the lower Jovian stratosphere is measured using the Galilean satellite eclipse technique. The average mixing ratio at the locations measured is larger than the expected value for a solar abundance of carbon with the expected value for a solar abundance of carbon with the possibility of some zenographic variation. Observationally compatible values are found for the South Temperate Zone, the edge of the Great Red Spot and the South Tropical Zone, and the Great Red Spot.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 44; Oct. 198
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  • 65
    Publication Date: 2011-08-18
    Description: Ten-micrometer spectra of the North Tropical Zone, North Equatorial Belt, and Great Red Spot at a spectral resolution of 1.1/cm are compared to synthetic spectra. These ground-based spectra were obtained simultaneously with the Voyager 1 encounter with Jupiter in March, 1979. The NH3 vertical distribution is found to decrease with altitude significantly faster than the saturated vapor pressure curve and is different for the three observed regions. Spatial variability in the NH3 mixing ratio could be caused by changes in the amount of NH3 condensation or in the degree of the NH3 photolysis. The C2H6 emission at 12 microns has approximately the same strength at the North Tropical Zone and North Equatorial Belt, but it is 30% weaker at the Great Red Spot. A cooler temperature inversion or a smaller abundance of C2H6 could explain the lower C2H6 emission over the Great Red Spot.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 44; Oct. 198
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  • 66
    Publication Date: 2011-08-18
    Description: Spectra of Pluto have been obtained on six nights during February 1979 by the use of the Cassegrain Digicon spectrograph on the 2.1-m Struve reflector and the IDS spectrograph on the 2.7-m reflector of McDonald Observatory. These spectra, with nominal resolution of 6-7 A, have been reduced to relative fluxes. Relative albedos were then calculated using the solar irradiances of Arvesen et al. (1969). The spectra taken in the blue show no indication of the upturn in albedo at wavelengths less than 3800 A previously reported by Fix, et al. (1970). The lack of a UV upturn cannot be interpreted in terms of a Rayleigh scattering atmosphere unless the albedo of the underlying surface is known. From the lack of methane absorption at the wavelength of the 6190- or 7270-A methane bands, an upper limit of 1-3 m-am of gaseous CH4 is derived. The albedo curve has a constant slope between 3500 and 7300 A. The only other solar system body which has this feature is an S-type asteroid.
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    Type: Icarus; 44; Oct. 198
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  • 67
    Publication Date: 2011-08-18
    Description: Titan was observed in four broad passbands between 35 and 150 microns. The brightness temperature in this interval is roughly constant at 76 plus or minus 3 K. Integrating Titan's spectrum from 5 to 150 microns yields an effective temperature of 86 plus or minus 3 K. Both the bright and dark hemispheres of Iapetus were observed in one broadband filter with a flux-weighted mean wavelength approximately equal to 66 microns. The brightness temperatures for these two sides of Iapetus are 96 plus or minus 9 K and 114 plus or minus 10 K, respectively. The bright-side Bond albedo is calculated to be 0.61(+0.16;-0.22).
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    Type: Icarus; 43; Sept
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  • 68
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    Publication Date: 2011-08-18
    Description: A physical model of the formation and growth of aerosols in the atmosphere of Titan has been constructed in light of the observed correlation between variations in Titan's albedo and the sunspot cycle. The model was developed to fit spectral observations of deep methane bands, pressures, temperature distributions, and cloud structure, and is based on a one-dimensional physical-chemical model developed to simulate the earth's stratospheric aerosol layer. Sensitivity tests reveal the model parameters to be relatively insensitive to particle shape but sensitive to particle density, with high particle densities requiring larger aerosol mass production rates to produce compatible clouds. Solution of the aerosol continuity equations for particles of sizes 13 A to about 3 microns indicates the importance of a warm upper atmosphere and a high-altitude mass injection layer, and the production of aerosols at very low aerosol optical depths. Limits are obtained for the chemical production of aerosol mass and the eddy diffusion coefficient, and it is found that an increase in mass input causes a decrease in mean particle size.
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    Type: Icarus; 43; Sept
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  • 69
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    Publication Date: 2011-08-18
    Description: The electromagnetic heating of the Io interior is considered as an alternative to tidal dissipation to account for the observed volcanic activity. The characteristics of the time-varying magnetic field of Jupiter as seen from Io are discussed, and the range of possible rock conductivities is examined. Interior heating due to the transverse electric and transverse magnetic modes is calculated. It is found that the TM mode appears to be insignificant as a heating source due to the high conductivity of the ionosphere, even when TM heating is concentrated in local hot regions. The TE mode is a more promising source of heating, although electromagnetic heating by either mode does not appear significant in comparison with other heat sources at present.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Dec. 10
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  • 70
    Publication Date: 2011-08-18
    Description: Spatially resolved spectra of Jupiter taken with the International Ultraviolet Explorer satellite show enhanced emissions from the polar regions at H L-alpha (1216 A) and in the Lyman and Werner bands of H2 (1175-1650 A). Two types of variability in emission brightness have been observed in these aurorae: an increase in the observed emission as the auroral oval rotates with Jupiter's magnetic pole to face toward the earth and a general variation in brightness of more than an order of magnitude under nearly identical observing conditions. In addition, the spectral character of these aurorae (determined by the ratio of H L-alpha to H2 brightnesses) appears variable, indicating that the depth of penetration of the auroral particles is not constant.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 241
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  • 71
    Publication Date: 2011-08-18
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal; vol. 241
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  • 72
    Publication Date: 2011-08-18
    Description: A fluid dynamical interpretation is presented of the two major types of disturbance found in the southern hemisphere of Jupiter by the Voyager 1 imaging data. The observed features always occur together, and consist of a compact elliptically shaped formation having an anticyclonic flow which is poleward of a pair of more elongated cyclonic structures, as in the Great Red Spot and the white ovals. It is noted that the anticyclonic features at 41 deg S may be described by the cnoidal wave solutions to the appropriate nonlinear evolution equation, and that flow patterns derived in the vicinity of the Great Red Spot and white ovals are strikingly similar to those obtained for the flow around a solitary wave of the type than can exist in a zonal flow such as that found in the Jupiter atmosphere. Results of computations in terms of solitary wave theory of flow fields in the atmospheric structure and zonal velocity profiles determined from Voyager infrared spectroscopy and radiometry data are then presented which show that the pattern must be a singular solitary wave mode, the east-west structure of which is best described by the Korteweg-de-Vries equation
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science; 210; Dec. 19
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  • 73
    Publication Date: 2011-08-18
    Description: The Gomez meteorite, weighing slightly over 47 kg, was found near the town of Gomez, Terry County, Texas (33 deg 10 min 53 sec N, 102 deg 24 min 5 sec W) prior to 1974. It is a highly weathered, equilibrated L-6 chondrite of composition Fa 26, Fs 23. A large number of chromite grains and possibly partially weathered lawrencite grains were noted.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Meteoritics; 15; Sept. 30
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  • 74
    Publication Date: 2011-08-18
    Description: The extent and mechanisms of global differentiation and the early thermal and tectonic histories of the terrestrial planets are surveyed in order to provide constraints on the first billion years of earth history. Indirect and direct seismic evidence for crusts on the moon, Mars and Venus is presented, and it is pointed out that substantial portions of these crusts have been in place since the cessation of heavy bombardment of the inner solar system four billion years ago. Evidence for sizable cores on Mars and Mercury and a small core on the moon is also discussed, and the heat involved in core formation is pointed out. Examination of the volcanic and tectonic histories of planets lacking plate tectonics indicates that core formation was not closely linked to crust formation on the moon or Mars, with chemical differentiation restricted to shallow regions, and was much more extensive on Mercury. Extension of these considerations to the earth results in a model of a hot and vigorously convecting mantle with an easily deformable crust immediately following core formation, and the gradual development of a lithosphere and plates.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Precambrian Research; 10; 1980
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  • 75
    Publication Date: 2011-08-18
    Description: The interaction of Io with its plasma torus and the Jovian magnetic field is described and examined in the context of several currently popular models. Three specific matters are addressed. First, features implied by sub-Alfvenic flow which must be common to all models are discussed. Next, the magnetic signature observed near Io by the Goddard Space Flight Center Voyager 1 magnetometer is examined and it is pointed out that the preliminary estimate of 5,000,000 A current may be an overestimate. Good fits are obtained with alternative current distributions which yield currents as small as 700,000 A through Io. The best fits are obtained for an Alfven Mach number of 0.15, but good fits are also found for Alfven Mach numbers between 0.1 and 0.25. Lastly, the crucial role of charged particle data for probing the near Io interaction is pointed out. Published data from the low energy charged particle (LECP) detector are made to suggest that Io has an intrinsic magnetic field of magnitude comparable with earlier estimates. Predictions are made which can test this picture as further data become available.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Nov. 1
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  • 76
    Publication Date: 2011-08-18
    Description: In the present paper, the single-scattering phase function of Saturn's aerosols is determined from the vertical structure of Saturn's atmosphere, derived in a previous analysis, and Pioneer's imaging photometry of bright and dark zones on Saturn in red and blue light. The single-scattering phase function is well represented by a combination of two Henyey-Greenstein functions. Moderately forward scattering functions fit well both in red and blue light, although a definite difference between the two colors is found.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Nov. 1
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  • 77
    facet.materialart.
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    Publication Date: 2011-08-18
    Description: The imaging photopolarimeter on Pioneer Saturn provided spin-scan images of Saturn's cloudtops. Only subtle departures from a uniform brightness distribution were apparent, except in the polar regions. At other latitudes the images show only a few features; they primarily support the conclusion that the visible atmosphere is a deep haze. Belts and zones are seen, and some detail in a zone near + or - 60 deg latitude. The North Equatorial Belt consists of two dark belts separated by a brighter zone exhibiting longitudinal structure.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Nov. 1
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  • 78
    Publication Date: 2011-08-18
    Description: The meteoroid penetration detectors on Pioneer 10 (channel 0) recorded 95 penetrations through the 25-micron stainless steel test material while the spacecraft was between 1 and 18 AU. The spatial density of 10 to the -9 g meteoroids is found to be essentially constant between 1 and 18 AU. The meteoroid penetration detectors on Pioneer 11 recorded 87 penetrations (55 on channel 0 and 32 on channel 1) through the 50-micron stainless steel test material while the spacecraft was between 1 and 9 AU. It is found that the meteoroids between 4 and 5 AU are not in direct circular or near-circular orbits near the ecliptic plane. The Pioneer 11 data obtained between 4 and 5 AU are best explained by the meteoroids being in randomly inclined orbits of high eccentricity. If meteoroids are in these cometlike orbits, the great increase in penetration flux previously measured near Jupiter with the Pioneer 10 experiment cannot be attributed to gravitational focusing unless the size distribution of meteoroids changes substantially between 1 and 5 AU. At Saturn encounter, the penetration flux increased by about three orders of magnitude, probably as the result of impacts from ring particles. Saturn's ring E is estimated to be 1800 km thick with an optical thickness greater than 10 to the -8.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Nov. 1
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  • 79
    Publication Date: 2011-08-18
    Description: The paper deals with measurements of the magnetic field along the outbound leg of Pioneer's trajectory at Saturn, which suggest that the spacecraft may have passed through the magnetic wake of Titan at a distance of 145 Titan radii downstream from Titan. The data obtained over a period of several hours around the crossing of Titan's L shell exhibit a number of characteristics which are qualitatively consistent with predictions based on theories of the interaction between a supersonic magnetized plasma and a conducting or magnetized planetary body. In addition, values of the plasma mass density derived from the interaction geometry are consistent with an upper limit inferred from in situ plasma measurements obtained during the outbound leg of Pioneer's trajectory.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Nov. 1
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  • 80
    Publication Date: 2011-08-18
    Description: The passage of Pioneer 11 through Saturn's magnetosphere revealed an especially intense region of high-energy particle fluxes that places unique constraints on models for sources of high-energy protons in the innermost radiation zones. Of special interest is the flux of protons with energies above 35 MeV which was measured with a fission cell in the innermost magnetosphere between the A ring and the orbit of Mimas. The negative phase space density gradients derived from the proton and electron observations in this region imply that steady-state inward diffusion from the outer magnetosphere is not an adequate source for these high-energy protons. In the present paper, the nature of the Crand source at Saturn is examined, and its significance for injection of high-energy protons into the region inside L = 4 is estimated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Nov. 1
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  • 81
    Publication Date: 2011-08-18
    Description: Electrons and protons of energies from 2 to 25 MeV and greater than 67 MeV, respectively, have been discovered throughout the entire equatorial region inward from the outer edge of the A ring at L = 2.3 to the periapsis of the Pioneer trajectory at L = 1.3. The trapped radiation found in Saturn's magnetosphere beyond L = 2.3 is totally absent here. The present paper deals with the measurements in this region under the rings, and their interpretation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research; 85; Nov. 1
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  • 82
    Publication Date: 2011-08-18
    Description: In the present paper, the average long-term effect of Saturn's satellite Mimas on the distribution of trapped radiation (macrosignature) is examined, along with a microsignature of satellite absorption, specifically, a brief dip in charged particle intensities observed on the inbound pass of Pioneer 11 as it passed through the orbital range of Mimas. It is hypothesized that it is indeed the shadow of Mimas, in the sense that the observations reveal the effect of this satellite on a distribution of particles which interacted with it in the recent past and then drifted in longitude to the observational location. The hypothesis led to a characterization of the electron energy spectrum in Saturn's inner magnetosphere and to an estimate of the radial diffusion coefficient for such electrons.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: AD-A093433 , Journal of Geophysical Research; 85; Nov. 1
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  • 83
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    Publication Date: 2011-08-17
    Description: A model is proposed for the early lunar evolution which accounts for the compositional asymmetry between the nearside and farside of the moon and the natural remanent magnetism of lunar rocks. According to the model, the preferred gravitational energy state consisted of an asymmetric accumulation of a liquid iron alloy (Fe-Ni and a small amount of sulfur) which displaces upwards the cold primordial undifferentiated core. The resulting depth asymmetry of the outer partially molten zone leads eventually to the subcrustal accumulation of light magnesium-rich pyroxenes and olivine, preferentially in one hemisphere, sufficient to explain the offset and also indirectly providing a possible explanation for the nearside concentration of KREEP and mass basalt. Slow downward migration of iron releases gravitational energy sufficient for convection and dynamo generation in an iron layer for about a billion years.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature; 287; Oct. 9
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  • 84
    Publication Date: 2011-08-17
    Description: Analysis of the concentration of 10 to 15 siderophile elements was made in the magnetic regions of Abee (E4) and Hvittis (E6). All elements, except Cu, W, and Fe were concentrated in the metal phase; unlike ordinary chondrites, the metal phase Abee and Hvittis consists of homogeneous, uniform grain size kamacite. The Ir/Ni ratio was 25% lower in Abee than in Hvittis, showing that more Ir was lost from Abee during the refractory element fractionation; Abee and other E4-5 members were not depleted in moderately volatile elements. It was concluded that E4-5 and E6 chondrites evolved from two different reservoirs, and that exchange of material among them has not occurred.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters; 48; 2, Ju; July 198
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  • 85
    Publication Date: 2011-08-17
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters; 47; 2, Ap; Apr. 198
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  • 86
    facet.materialart.
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    In:  Other Sources
    Publication Date: 2011-08-17
    Description: It is proposed that a vapor explosion of a submerged pool of liquid sulfur will remove the crust overlying an area of about 50-km diam. Thermal radiation from the exposed liquid sulfur pool with a surface temperature of 600 K is then presumed to be responsible for the 5-micron outbursts that have been observed. The explosive volcanoes are expected to leave black sulfur calderas, which are, indeed, found on the surface. The 5-micron outburst observed by Sinton (1980), on June 11, 1979 (UT), is identified with a new caldera found on Voyager 2 photographs but which had not been present on Voyager 1 pictures.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus; 43; July 198
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  • 87