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  • 1
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    In:  Other Sources
    Publication Date: 2011-08-24
    Description: Detecting and imaging small wildfires with an Airborne Scanner is done against generally high background levels. The Airborne Scanner System used is a two-channel thermal IR scanner, with one channel selected for imaging the terrain and the other channel sensitive to hotter targets. If a relationship can be determined between the two channels that quantifies the background signal for hotter targets, then an algorithm can be determined that removes the background signal in that channel leaving only the fire signal. The relationship can be determined anywhere between various points in the signal processing of the radiometric data from the radiometric input to the quantized output of the system. As long as only linear operations are performed on the signal, the relationship will only depend on the system gain and offsets within the range of interest. The algorithm can be implemented either by using a look-up table or performing the calculation in the system computer. The current presentation will describe the algorithm, its derivation, and its implementation in the Firefly Wildfire Detection System by means of an off-the-shelf commercial scanner. Improvement over the previous algorithm used and the margin gained for improving the imaging of the terrain will be demonstrated.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: Infrared technology XVII; Proceedings of the Meeting, San Diego, CA, July 22-26, 1991 (A93-38376 15-35); p. 207-212.
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  • 2
    Publication Date: 2011-08-24
    Description: The size and complexity of AVIRIS data sets makes analysis difficult. We present a technique that allows the researcher to rapidly scan the full data set in image form in order to empirically find significant spatial patterns anywhere across the spectrum. Our approach takes advantage of the speed and power of computer graphics workstations to allow real-time, interactive data manipulation and display. Empirical data selection avoids the bias inherent in theoretical selection criteria, and allows discovery of unexpected relationships within the data set. Link Winds, a prototype data analysis system under development, provides the visualization tools used in this study. We are applying this approach to geological studies in the eastern Mojave Desert.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: Thematic Conference on Geologic Remote Sensing, 8th, Denver, CO, Apr. 29-May 2, 1991, Proceedings. Vol. 1 (A93-28978 10-43); p. 423-426.
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  • 3
    Publication Date: 2011-08-24
    Description: Current atmospheric correction models applied to imaging spectroscopy data include such methods as residual or scene average, flat field correction, regression method or empirical line algorithm, the continuum interpolated band ratio (CIBR) derivation and the LOWTRAN 7 method. Due to the limitations of using residual and flat field corrections on vegetated scenes, three methods will be compared: regression, CIBR derivation and LOWTRAN 7. Field-measured bright and dark targets taken at the time of the 13 April, 1989 AVIRIS overflight of Jasper Ridge, California were used to formulate the regression method atmospheric correction. Using this corrected scene as 'ground truth', the CIBR derivation and the LOWTRAN 7 method with both input models are compared on the vegetated Jasper Ridge scene. Although representing a qualitative approach, this is a first approximation and shows the need for more quantitative analysis.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: Thematic Conference on Geologic Remote Sensing, 8th, Denver, CO, Apr. 29-May 2, 1991, Proceedings. Vol. 1 (A93-28978 10-43); p. 413-421.
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  • 4
    Publication Date: 2011-08-24
    Description: This paper provides a guide for the acquisition, processing, and interpretation of Landsat Thematic Mapper (TM) imagery of desert terrains for use in regional exploration. Sun angle considerations, data quality cautions, noise suppression routines, band selections, data calibration, spectral enhancements, perceptual considerations of displays, and general interpretation guidelines are all discussed as components of an image-information extraction procedure.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: Thematic Conference on Geologic Remote Sensing, 8th, Denver, CO, Apr. 29-May 2, 1991, Proceedings. Vol. 1 (A93-28978 10-43); p. 277-285.
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  • 5
    Publication Date: 2011-08-24
    Description: The NASA Thermal Infrared Multispectral Scanner (TIMS) has been successfully used for the remote identification of a variety of soil and aggregate deposits in vegetated areas of two states. Over three million cubic meters of gravel deposits were identified from the imagery during a two year period. Verification was accomplished by ground reconnaissance using drilling machinery and by ground instrumentation. The method has been used to differentiate between fine and coarse grained soils, and gravel deposits. The deposits were found to have been naturally sorted according to grain size by depositional processes, providing each deposit with distinct spectral qualities. It was found that the masking effects of relatively dense vegetation were largely overcome by using imagery acquired at higher altitudes above terrain than 9000 meters, due to loss of resolution of the finer detail. The mechanics of image resolution are discussed, a method of data analysis used is described, and sample spectral signatures are illustrated.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: In: Earth and atmospheric remote sensing; Proceedings of the Meeting, Orlando, FL, Apr. 2-4, 1991 (A93-24176 08-42); p. 358-369.
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  • 6
    Publication Date: 2011-08-24
    Description: Viewing terrain data from various remote sensors in three dimensions has proven to be a valuable tool for scientists in understanding a variety of problems. A technique is presented for using image pyramids in such visualization of large terrain data sets, providing up to two orders of magnitude performance enhancement over simpler techniques, while at the same time eliminating false high-frequency information, which causes animations to sparkle.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Imaging Systems and Technology (ISSN 0899-9457); p. 157-166.
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  • 7
    Publication Date: 2011-08-24
    Description: An evaluation was performed on SWIR (2000-2400 nm) data from two airborne remote sensing systems for discriminating and identifying alteration minerals at Cuprite, Nevada. The data were acquired by the NASA Airborne Visible/InfraRed Imaging Spectrometer (AVIRIS) and the GEOSCAN Mk II multispectral scanner. The evaluation involved comparison of processed imagery and image-derived spectra with existing alteration maps and laboratory spectra of rock samples from Cuprite. Results indicate that both the AVIRIS and GEOSCAN data permit the discrimination of areas of alunite, buddingtonite, kaolinite, and silicification using color composite images formed from three SWIR bands processed with either the decorrelation stretch or a log residual algorithm. The laboratory spectral features alunite, kaolinite and buddingtonite could be seen clearly only in the log residual processed AVIRIS data. However, this does not preclude their identification with the GEOSCAN data.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Geophysics (ISSN 0016-8033); 56; 9; p. 1432-1440.
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  • 8
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    In:  Other Sources
    Publication Date: 2011-08-24
    Description: Preliminary results are presented of observations of Mars using three telescopes and a CCD camera, grating-array spectrometers, and a near-IR array camera. Martian albedo features are shown to be similar in the visible and 1.3-3.5-micron range, and reflectances of nearly zero are noted in the image at 3.02 microns. The results demonstrate that these techniques provide effective maps of spatial variations in spectral absorption features caused by Martian atmospheric volatiles and by surface minerals.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: EOS (ISSN 0096-3941); 72; 47, N; 521
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  • 9
    Publication Date: 2011-08-24
    Description: The present work describes the mission operations system (MOS) design process for remote-sensing missions. A MOS is defined as the system required to perform, monitor, and control an operation, encompassing personnel, hardware, software and/or documentation. Attention is given to telecommunications and remote-sensing instrumentation, MOS definition program phases and reviews, and MOS organization, management, and staffing. Also treated are the uplink and downlink processes, anomalies and contingency plans, the illustrative case of the MOS for the Magellan radar sensing mission, and a projection of future MOSs incorporating AI.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
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  • 10
    Publication Date: 2011-08-24
    Description: After detailing a technique for the estimation of the instantaneous emission of trace gases produced by biomass burning, using satellite imagery, attention is given to the recent discovery that burning results in significant enhancement of biogenic emissions of N2O, NO, and CH4. Biomass burning accordingly has an immediate and long-term impact on the production of atmospheric trace gases. It is presently demonstrated that satellite imagery of fires may be used to estimate combustion emissions, and could be used to estimate long-term postburn biogenic emission of trace gases to the atmosphere.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
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  • 11
    Publication Date: 2011-08-24
    Description: One of the largest forest fires ever recorded burned in the People's Republic of China (PRC) and the Soviet Union in May 1987. The fire covered over 1.0 million hectares in the PRC and almost 4 million hectares in the Soviet Union. The progress and areal extent of the fire were measured using satellite images analyzed in the imaging facilities at NASA-Langley and Forestry Canada. The analyses show the utility and value of satellite measurements to assess the areal extent and geographical distribution of fires, and have important implications for future measurements to be obtained from space platforms, such as the Earth Observing System.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
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  • 12
    Publication Date: 2011-08-24
    Description: The application of remote sensing to ecological investigations is briefly discussed. Emphasis is given to the recruitment problem in marine population dynamics, the regional analysis of terrestrial ecosystems, and the monitoring of ecological changes. Impediments to the use of remote sensing data in ecology are addressed.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Ecology (ISSN 0012-9658); 72; 6, De
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  • 13
    Publication Date: 2011-08-24
    Description: Some of the most significant earth-viewing imagery obtained during Space Shuttle Columbia's flight STS-35, December 2-10, 1990, is reviewed with emphasis on observations of the Southern Hemisphere. In particular, attention is given to environmental observations in areas of Madagascar, Brazil, and Persian Gulf; observation of land resources (Namibia, offshore Australia); and observations of ocean islands (Phillipines, Indonesia, and Reunion). Some of the photographs are included.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Geocarto International (ISSN 1010-6049); 6; 4, De
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  • 14
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    In:  CASI
    Publication Date: 2005-08-04
    Description: Use of current space imaging systems and airborne platforms has direct use in survey design and site location when used in concert with a comprehensive GIS environment. Local conditions and site physical and chemical properties are key factors in successful applications. Conjoining of environmental constraints and site properties are present for the later prehistoric occupations in the Arkansas and Mississippi River areas. Direct linkages between comprehensive site databases and satellite images can be used to evaluate site distributions for research and management.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA. Stennis Space Center, Applications of Space-Age Technology in Anthropology; p 237-250
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  • 15
    Publication Date: 2005-08-04
    Description: Creating rain forest reserves is vital given the global decline in biodiversity. Yet, the plants and animals that will be protected from untrammeled commercial exploitation within such reserves constitute essential resources for indigenous foragers and farmers. Balancing the needs of local subsistence level populations with the goals of national and international conservation agencies requires a thorough understanding of the mutual impacts that arise from the interaction of park and people. In the Ituri forest of Zaire, LANDSAT TM image analysis and GPS ground truth data were used to locate human settlements so that boundaries of the proposed Okapi Reserve could be chosen to minimize its impact on the subsistence practices of the local foragers and farmers. Using satellite imagery in conjunction with cultural information should help to ensure traditional resource exploitation rights of indigenous peoples whilst simultaneously protecting the largest contiguous area of undisturbed forest.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA. Stennis Space Center, Applications of Space-Age Technology in Anthropology; p 181-193
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  • 16
    Publication Date: 2005-08-04
    Description: A wide variety of remote sensing instruments have been utilized to attempt to detect archaeological features under volcanic ash in Central America. Some techniques have not been successful, such as seismic refraction, for reasons that are not difficult to understand. Others have been very successful and provide optimism for archaeologists witnessing the destruction of unburied sites throughout Central America. The sudden burial of buildings, gardens, and footpaths by volcanic ash can preserve them extremely well providing a rich data base for understanding human life and culture at certain points in time.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA. Stennis Space Center, Applications of Space-Age Technology in Anthropology; p 167-179
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  • 17
    Publication Date: 2005-08-04
    Description: The concept of integrating ecological perspectives on early man's settlement patterns with advanced remote sensing technologies shows promise for predictive site modeling. Early work with aerial imagery and ecosystem analysis is discussed with respect to the development of a major project in Maya archaeology supported by NASA and the National Geographic Society with technical support from the Mississippi State Remote Sensing Center. A preliminary site reconnaissance model will be developed for testing during the 1991 field season.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Applications of Space-Age Technology in Anthropology; p 121-136
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  • 18
    Publication Date: 2005-08-04
    Description: A Geographic Information System (GIS)-type analysis of archaeological site locations using a dBase III plus program and a desk top computer is presented. A previously developed model of site locations in the Sequatchie Valley of northeastern Alabama is tested against known site locations in another large survey area there. The model fails to account for site locations in the test area. A model is developed for the test area and indicates the site locations are indeed different. Whether this is due to differences in site locations on a sub-regional level, or to sample error in the original model is unknown.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA. Stennis Space Center, Applications of Space-Age Technology in Anthropology; p 95-110
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  • 19
    Publication Date: 2005-08-04
    Description: Data recovered as the result of a recent field project designed to test a model of the distribution of protohistoric settlement in an unusual physiographic zone in eastern Mississippi are examined using GIS based techniques to manipulate soil and stream distance information. Significant patterning is derived. The generally thin soils and uniform substratum of the Black Prairie in combination with a distinctive settlement pattern offer a promising opportunity for the search for site specific characteristics within airborne imagery. Landsat TM data provide information on modern ground cover which is used as a mask to select areas in which a multivariate search for archaeological site signatures within a TIMS image is most likely to prove fruitful.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA. Stennis Space Center, Applications of Space-Age Technology in Anthropology; p 111-120
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  • 20
    Publication Date: 2005-08-04
    Description: A Macro-geographical reconnaissance of the Western Peloponnesos adopts spectral signatures taken by Landsat-5 Thematic Mapper as a new instrument of archaeological survey in Greece. Ancient records indicate that indigenous resources contributed to the prosperity of the region. Natural resources and Ancient, Medieval, and Pre-modern Folklife in the Western Peloponnesos describes the principal lines of research. For a supervised classification of attested ancient resources, a variety of biophysical surface features were pinpointed: stone quarries, coal mines, forests of oak and silver fir, terracotta-producing clay beds, crops, and various wild but exploited shrubs such as flax.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: NASA. Stennis Space Center, Applications of Space-Age Technology in Anthropology; p 63-79
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  • 21
    Publication Date: 2006-06-13
    Description: In the TOPEX/POSEIDON project, several satellite positioning systems, such as Laser, Doppler Orbitography and Radiopositioning Integrated by Satellite (DORIS), and Global Positioning Satellite (GPS) (on an experimental basis), will be used to track the satellite and to provide accurate orbits. Unfortunately, these systems will provide their dedicated tracking-station coordinates and the satellite orbits in different reference frames. Each technique will use, de facto, a different reference frame. In fact, even for the same technique, each group, depending on the hypothesis used in its computation, will use a different reference frame. This problem is not new for geodesists and can be overcome, in large part, but could create trouble for other scientists when they compare or combine different coordinate data sets. The main purpose of this investigation is to determine a consistent terrestrial system for TOPEX/POSEIDON in which all the tracking-station coordinates, all the orbit ephemerides, and all the other station coordinates of specific interest (such as tide gauges) could be expressed. Another issue of this investigation is the provision of reliable information concerning the relationships between all the possible reference frames of interest for th TOPEX/POSEIDON project. To be more explicit, we plan to provide the possible transformation formula between the TOPEX/POSEIDON terrestrial reference frame and the Laser, DORIS, GPS, and other internationally recognized frames such as the International Terrestrial Reference Frame (ITRF).
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: JPL, TOPEX(Poseidon Science Investigations Plan; p 27-28
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  • 22
    Publication Date: 2006-06-13
    Description: Our program includes five research items: (1) determination of a precision geoid and gravity anomaly field; (2) precise leveling and detection of tidal changes of the sea surface and study of the role of the tide in the global energy exchange; (3) oceanic effect on the Earth's rotation and polar motion; (4) geological and geophysical interpretation of the altimetry gravity field; and (5) evaluation of the effectiveness of local tracking of TOPEX/POSEIDON by use of a laser tracker.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: JPL, TOPEX(Poseidon Science Investigations Plan; p 126-130
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  • 23
    Publication Date: 2011-08-24
    Description: A model for estimating wheat yields on the farm level was developed, that integrates the Landsat TM data and agrometeorological information. Results obtained for a test site in southern Brasil for years of 1986 and 1987 show that the vegetation index derived from Landsat TM could account for the 60 to 40 percent wheat-yield variability observed between the two crop years. Compared to results using either the Landsat TM vegetation index or the agrometeorological data alone, the joint use of both types of data in a single model yielded a significant improvement.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 12; 2477-248
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  • 24
    Publication Date: 2011-08-24
    Description: The complex nature of the Uranus radio emissions, both magnetospheric and atmospheric, is reviewed, with emphasis on the identification of distinct components and the determination of their source locations. Seven radii components were discovered in addition to the RF signature of lightning in the planet's atmosphere. Six of the seven magnetospheric components are freely propagating emissions; one component, the nonthermal continuum, is trapped in the density cavity between the magnetopause and the dense inner magnetosphere. The radio components are divided into two types according to their emission signature: bursty emission and smooth emission. The inferred source location for the dominant nightside emission is above the nightside magnetic pole, largely overlapping the UV auroral region and the magnetic polar cap. The N-burst component appears to be associated with solar-wind enhancements at Uranus, consistent with the idea that the solar wind was triggering magnetospheric substormlike activity during the encounter.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 25
    Publication Date: 2011-08-24
    Description: The energetic particle measurements by the low-energy charged-particle and cosmic-ray instruments on the Voyager 2 spacecraft in the magnetosphere of Uranus are reviewed. Upstream events were observed outside the Uranian bow shock, probably produced by ion escape from the magnetosphere. Evidence of earthlike substorm activity was discovered within the Uranian magnetosphere. A proton injection event was observed within the orbit of Umbriel and proton events were observed in the magnetotail plasma-sheet boundary layer that are diagnostic of earthlike substorms. The magnetospheric composition is totally dominated by protons, with only a trace abundance of H(2+) and no evidence for He or heavy ions; the Uranian atmophere is argued to be the principal plasma source. Phase-space densities of medium energy protons show inward radial diffusion and are quantitatively similar to those observed at the earth, Jupiter, and Saturn. These findings and plasma wave data suggest the existence of structures analogous to the earth's plasmasphere and plasmapause.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 26
    Publication Date: 2011-08-24
    Description: An overview of the observational results on the plasma environment at Uranus is given, and the implications of these observations for magnetospheric physics at Uranus are discussed. During the Voyager 2 encounter with Uranus, an extended magnetosphere filled with a tenuous plasma was detected. This low-energy plasma was found to consist of protons and electrons, with no significant heavy ion contribution, and with a density in the regions sampled by the spacecraft of at most three electrons per cubic centimeter. The plasma electrons and ions exhibit both a thermal component (with temperatures of tens of eV) and a hot component (with temperatures of a few keV). The thermal ion component is observed both inside and outside an L-shell value near 5, whereas the hot ion and electron component is excluded from the region inside of that L-shell. The source of the thermal component of the plasma is either the planetary ionosphere or the neutral hydrogen corona surrounding Uranus, whereas the hot component is convected in from the magnetotail, with probably an ionospheric source.
    Keywords: LUNAR AND PLANETARY EXPLORATION
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  • 27
    Publication Date: 2011-08-24
    Description: Airborne and satellite passive microwave measurements acquired simultaneously with ground measurements of depth, density, and stratigraphy of the snow in central and northern Alaska between March 11 and 19, 1988, are reported. A good correspondence in brightness temperature (TB) trends between the aircraft and satellite data was found. An expected inverse correlation between depth hoar thickness and TB was not found to be strong. A persistent TB minimum in both the aircraft and the satellite data was detected along the northern foothills of the Brooks Range. In an area located at about 68 deg 60 min N, 149 deg 20 min W, the TB as recorded from the aircraft microwave sensor dropped by 55 K. Satellite microwave measurements showed a TB decrease of up to 45 K at approximately the same location. An examination of microwave satellite data from 1978 to 1987 revealed that similar low late-winter values were found in approximately the same locations as those observed in March 1988.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Remote Sensing of Environment (ISSN 0034-4257); 38; 161-172
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  • 28
    Publication Date: 2011-08-24
    Description: Recent telescopic observations have led to the identification of cyanogroup-containing molecules in the dark surface solids of several D-class asteroids, cometary dusts, and the rings of Uranus, as well as the low-albedo atmosphere of Iapetus. The occurrence of the 2.2-micron overtone of C triple-bond N's stretching fundamental mode in all four classes of small solar system bodies is presently suggested to serve as a diagnostic of both exposure duration and degree of modification of surface materials.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 94; 345-353
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  • 29
    Publication Date: 2011-08-24
    Description: The Michigan Microwave Canopy Scattering Model (MIMICS) is used to model scatterometer data that were obtained during the August 1987 EOS (Earth Observing System) synergism study. During this experiment, truck-based scatterometers were used to measure radar backscatter from a walnut orchard in Fresno County, California. Multipolarized L- and X-band data were recorded for orchard plots for which dielectric and evapotranspiration characteristics were monitored. MIMICS is used to model a multiangle data set in which a single orchard plot was observed at varying impedance angles and a series of diurnal measurements in which backscatter from this same plot was measured continuously over several 24-h periods. MIMICS accounts for variations in canopy backscatter driven by changes in canopy state that occur diurnally as well as on longer time scales. L-band backscatter is dependent not only on properties of the vegetation but also on properties of the underlying soil surface. The behavior of the X-band backscatter is dominated by properties of the tree crowns.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: IEEE Transactions on Geoscience and Remote Sensing (ISSN 0196-2892); 29; 852-863
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  • 30
    Publication Date: 2011-08-24
    Description: A quantitative analysis of error sources in 1D planetary photoclinometry is presented. The technique is affected by error sources arising from the spacecraft image, the planetary body, and the scan line orientation. Slope errors are calculated for each of these sources, using examples of Voyager imaging of Ganymede and Viking orbiting imaging of Mars. Slope errors are investigated for a variety of viewing and lighting geometries, slope angles, and slope orientations. The results are broken down into nonsystematic and systematic errors. Derivations that allow the calculation of photoclinometric slope errors for any photometric function are presented, and the implications of these results for 2D photoclinometric techniques are discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 20
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  • 31
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    Publication Date: 2011-08-24
    Description: A morphometric analysis of north-south trending graben at 35 deg N in northern Tharsis is used to provide the first quantitative measurements of crustal extension in and strain for areas of the Martian crust that have undergone both extreme and mild deformation. These estimates also demonstrate the viability of the Viking data for making such quantitative assessment. Graben in the region accommodate about 8 km of post Early Amazonian east-west extension. This extension corresponds to a net regional strain of 0.45-0.61 percent; local strains vary from less than 1 percent to 5 percent. Extension is nonuniform and localized near 110 deg (south of Alba Patera and north of Ceraunius Fossae) because of reactivation of preexisting fractures in underlying basement and possibly due to superposition of stress fields from Tharsis and Alba Patera. A major mechanical discontinuity in the shallow crust, probably representing the base of or a strength contrast within the megaregolith, is observed. It occurs at a depth of 2 km on the profile flanks and is depressed to about 7.5 km near 110 deg due to loading of the crust by the volcano.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 18
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  • 32
    Publication Date: 2011-08-24
    Description: Airborne Visible/Infrared Imaging Spectrometer data covering the wavelength range between 2000 and 2400 nm are examined for their ability to display the diagnostic mineral absorption features of certain alteration minerals, employing various data processing techniques. The techniques may be separated into two broad categories: scene based techniques that use parameters derived from the data themselves, and correction techniques utilizing external information such as solar/atmospheric models. Results indicate that the data corrected utilizing the LOWTRAN 7 atmospheric transfer code constrained with local weather station data are the most effective at showing the diagnostic absorption features of the regions of known mineralogy and introduce the least number of artifacts into the data.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Photogrammetric Engineering and Remote Sensing (ISSN 0099-1112); 57; 1303-130
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  • 33
    Publication Date: 2011-08-19
    Description: The authors present the results of an experiment using the NASA/JPL DC-8 AIRSAR (aircraft synthetic-aperture radar) over a coniferous forest near Mt. Shasta (California) in 1989. Calibration devices were deployed in clearings and under the forest canopy and passes at 20, 40, and 55 deg incidence angles were made with the AIRSAR. A total of eight images at differing incidence angles have been processed and calibrated. The multipolarization, multifrequency data were examined, and it was found that the C-band cross section averaged over like and cross polarizations is the best parameter for distinguishing between two stands with differing forest biomass. The average cross section at P- and L-bands is useful only for smaller incidence angles. Parameters describing the polarization behavior of the scattering were primarily useful in identifying the dominant scattering mechanisms for forest backscatter. It was found that both branch scattering and ground/tree interactions are important at P-band. At L-band and C-bands, the return is primarily from the canopy. Comparison with model calculations verified this conclusion.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: IEEE Transactions on Geoscience and Remote Sensing (ISSN 0196-2892); 29; 444-450
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  • 34
    Publication Date: 2011-08-19
    Description: All orders of scattering are analyzed for two artifical canopies. The SHL canopy consists of Small Horizontal Leaves that are much smaller than the leaf-to-leaf spacing. The IHL canopy consists of Infinite Horizontal Layers, where each leaf is of infinite extent (a horizontal plane). Hemispheric leaf reflectances and transmittances independent of the direction of illumination lead to exact solutions for these models. Sunlight that penetrates to a given leaf area index level is much stronger in an SHL canopy than that in IHL; but the difference becomes muted when leaf transmittance is large. Multiple scattering enhances the hemispheric canopy reflectance more strongly in SHL than it does in IHL. The enhancement depends linearly on leaf transmittance in SHL and on the transmittance squared in IHL. Comparison with measured reflectances indicates that IHL model grossly underestimates multiple scattering in soybean canopies.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Applied Optics (ISSN 0003-6935); 30; 1562-156
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  • 35
    Publication Date: 2011-08-19
    Description: The Martian southern hemisphere atmospheric water vapor column abundance measurements reported agree with Viking Orbiter atmospheric water detectors during early southern spring and southern autumnal equinox; profiles obtained in southern mid- and late summer, however, indicate the presence of twice as much water both in the southern hemisphere and planetwide. This discrepancy is accounted for by the high optical depths created by two global dust storms during the Viking year, while the present observations were obtained in the case of the relatively dust-free atmosphere of the 1988-1989 opposition.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 90; 205-213
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  • 36
    Publication Date: 2011-08-19
    Description: A spatially variable monthly, infrared cloud-threshold data base has been used to screen cloud-contaminated observations from radiances measured by the NOAA-9 AVHRR over Africa. Cloud-screening through a monthly average infrared threshold based on measured surface air temperature, which is geographically dependent, shows an improvement over using a seasonally and geographically independent thermal cloud threshold of 287 K. It is found that differences in cloud-screening for these two thresholds occur for cases of lower altitude clouds or subpixel clouds where the radiative temperature is higher than the 287 K infrared threshold, yet colder than the variable threshold developed by Stowe et al. (1988) for the Nimbus-7 global cloud climatology. The variable IR threshold is shown to be effective over persistently cloud-covered regions, such as the coastal region of the Gulf of Guinea, but may introduce some erroneous cloud identifications over mountains.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 12; 1205-122
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  • 37
    Publication Date: 2011-08-19
    Description: In order to monitor the aerosol characteristics needed for atmospheric correction of remotely sensed data, a network of sun photometers was established in the Sahel region of Senegal, Mali, and Niger. Data analysis suggests that there is a high spatial variability of the aerosol optical thickness tau(a) in the western Sahel region. At a 67 percent confidence level the instantaneous values of tau(a) can be extrapolated approximately 270-400 km with an error tolerance of 50 percent. Spatial variability in the dry season is found to be of a similar magnitude. The ranges of variations in the NDVI in the Sahel region are shown to be approximately 0.02 and 0.01, respectively, due to commonly observed fluctuations in the aerosol optical thickness and aerosol size distribution.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 12; 1147-116
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  • 38
    Publication Date: 2011-08-19
    Description: Images are presented that show the mean and coefficient of variation of nine years (1981-1989) of NOAA AVHRR normalized difference vegetation index (NDVI) data for the growing season (July-October) in Africa, north of the equator. The variation in the growing season NDVI is represented by the coefficient of variation image that shows the large variation in the Sahelian growing season between years. It is concluded that these images illustrate some aspects of the perspective being brought to regional and continental scale processes by coarse resolution satellite sensors and the potential of these sensors to provide consistent, long-term datasets.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 12; 1133-113
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  • 39
    Publication Date: 2011-08-19
    Description: Near-infrared spectra of a bright and a dark thermal emission feature on the night side of Venus have been obtained from 2.2 to 2.5 microns at a spectral resolution of 1200 to 1500. Both bright and dark features show numerous weak absorption bands produced by CO2, CO, water vapor, and other gases. The bright feature emits more radiation than the dark feature throughout this spectral region, but the largest contrasts occur between 2.21 s 2.32 microns, where H2SO4 clouds and a weak CO2 band provide the only known sources of extinction. The contrast decreases by 55 to 65 percent at wavelengths longer than 2.34 microns, where CO, clouds, and water vapor also absorb and scatter upwelling radiation. This contrast reduction may provide direct spectroscopic evidence for horizontal variations in the water vapor concentrations in the Venus atmosphere at levels below the cloud tops.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 252; 1293-129
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  • 40
    Publication Date: 2011-08-19
    Description: Magellan images confirm that volcanism is widespread and has been fundamentally important in the formation and evolution of the crust of Venus. High-resolution imaging data reveal evidence for intrusion (dike formation and cryptodomes) and extrusion (a wide range of lava flows). Also observed are thousands of small shield volcanoes, larger edifices up to several hundred kilometers in diameter, massive outpourings of lavas, and local pyroclastic deposits. Although most features are consistent with basaltic compositions, a number of large pancake-like domes are morphologically similar to rhyolite-dacite domes on earth. Flows and sinuous channels with lengths of many hundreds of kilometers suggest that extremely high effusion rates or very fluid magmas (perhaps komantiites) may be present. Volcanism is evident in various tectonic settings (coronae, linear extensional and compressional zones, mountain belts, upland rises, highland plateaus, and tesserae). Volcanic resurfacing rates appear to be low (less than 2 cu km/yr) but the significance of dike formation and intrusions, and the mode of crustal formation and loss remain to be established.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 252; 276-288
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  • 41
    Publication Date: 2011-08-19
    Description: Mars exploration crews will be exposed to such high radiation dosages in route from earth that as to sharply reduce the allowable dose they should receive while on the Martian surface. An account is presently given of the possibility of using Martian regolith as crew shielding to maintain very low short-term dose limits. NASA-Langley's nucleon and heavy-ion transport computer codes are used to predict the propagation and interaction of the free-space nucleons and heavy ions through the Martian atmosphere and then through various thicknesses of regolith. The largest reduction in dose occurs in the first 15-20 cm of regolith material.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Spacecraft and Rockets (ISSN 0022-4650); 28; 7
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  • 42
    Publication Date: 2011-08-19
    Description: Accelerator mass spectrometry is utilized to determine the half-life of Ca-41 from the decrease of its concentration with terrestrial age in five Antarctic meteorites and a recent fall. The meteorites were selected on the basis of their Cl-36 concentrations, which showed a span of terrestrial ages of about 600 ka, and on the basis of other cosmogenic nuclide concentrations which indicated that the meteorites had small preatmospheric sizes, and sufficiently long irradiation times in space that the concentrations of Ca-41 and Cl-36 were in secular equilibrium prior to the meteorites' fall to earth. The half-life of Ca-41 is determined at 103 + or - 7 ka. Topics discussed include the effects of undersaturation (short exposure time in space), shielding (the samples are from the interior of a large meteorite), and weathering on the cosmogenic nuclide concentrations in meteorites.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters (ISSN 0012-821X); 103; 1-4,; 79-83
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  • 43
    facet.materialart.
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    Publication Date: 2011-08-19
    Description: Analytic expressions are derived to model the surface topography and the normal to the surface of Phobos. The analytic expressions are comprised of a spherical harmonic expansion for the global figure of Phobos, augmented by addition terms for the large crater Stickney and other craters. Over 300 craters were measured in more than 100 Viking Orbiter images to produce the model. In general, the largest craters were measured since they have a significant effect on topography. The topographic model derived has a global spatial and topographic accuracy ranging from about 100 m in areas having the highest resolution and convergent, stereo coverage, up to 500 m in the poorest areas.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Planetary and Space Science (ISSN 0032-0633); 39; 355-376
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  • 44
    Publication Date: 2011-08-19
    Description: From February to March 1989 the Phobos 2 spacecraft took 37 TV images of Phobos at a distance of 190-1100 km. These images complement Mariner-9 and Viking data by providing higher-resolution coverage of a laarge region west of the crater Stickney (40-160 deg W) and by providing disk-resolved measurements of surface brightness at a greater range of wavelengths and additional phase angles. These images have supported updated mapping and characterization of large craters and grooves, and have provided additional observations of craters' and grooves' bright rims. Variations in surface visible/near-infrared color ratio of almost a factor of 2 have been recognized; these variations appear to be associated with the ejecta of specific large impact craters. Updated determinations of satellite mass and volume allow calculation of a more accurate value of bulk density, 1.90 + or - 0.1 g/cu cm. This is sigificantly lower than the density of meteoritic analogs to Phobos' surface, suggesting a porous interior perhaps containing interstitial ice.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Planetary and Space Science (ISSN 0032-0633); 39; 281-295
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  • 45
    Publication Date: 2011-08-19
    Description: A new image enlargement and reconstruction routine, the digital image enlarging balanced reconstruction algorithm (DIEBRA), is described. Using a highly modified form of 'balanced' two-dimensional polynomial interpolation, this program enlarges digital imagery, creating synthetic high spatial resolution images. Statistical analysis shows the DIEBRA-generated imagery to be significantly closer to true high spatial resolution imagery at all frequencies than imagery generated by a cubic convolutional reconstruction filter.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 12; 627-634
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  • 46
    facet.materialart.
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    Publication Date: 2011-08-19
    Description: The morphology and temporal variability of the Venus ionosphere are characterized, reviewing the results of recent theoretical investigations, observations, and in situ measurements, especially by the Pioneer Venus Orbiter (PVO). Consideration is given to the Pioneer mission and orbit evolution, early radio occultation profiles of ionospheric N(e), the mean structure and thermal balance of the ionosphere, the ion composition and its dawn-dusk asymmetry, the small-scale spatial structure on the nightside, latitudinal and seasonal variations, solar-cycle effects, suprathermal electrons and superthermal ions, and the global configuration and stability of the ionopause. Data from a single PVO passage through the ionotail are discussed in detail, examining the implications for ion escape and the solar-cycle and short-term variability. The differences among the terrestrial, Martian, and Venusian ionospheres are outlined; the PVO data base is described; and the sources of measurement error are indicated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Space Science Reviews (ISSN 0038-6308); 55; 81-163
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  • 47
    Publication Date: 2011-08-19
    Description: Irrigated rice provides an ideal breeding habitat for Anopheles free-borni, the western malaria mosquito, throughout California. In a 1985 study, it was determined that early-season rice canopy development, as monitored using remotely sensed data, could be used to distinguish between high and low mosquito producing rice fields. This distinction could be made over two months prior to peak mosquito production. It was found that high-producing fields were located in an area characterized by a diversity of land use, including livestock pastures, whereas the low-producing fields were in an area devoted almost exclusively to the cultivation of rice. The ability to distinguish between high and low mosquito producing fields prior to peak mosquito production is important in terms of mosquito habitat surveillance and control.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 12; 621-626
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  • 48
    Publication Date: 2011-08-19
    Description: Internal heat flow from radioactive decay in Triton's interior along with absorbed thermal energy from Neptune total 5 to 20 percent of the isolation absorbed by Triton, thus comprising a significant fraction of Triton's surface energy balance. These additional energy inputs can raise Triton's surface temperature between about 0.5 and 1.5 K above that possible with absorbed sunlight alone, resulting in an increase of about a factor of about 1.5 to 2.5 in Triton's basal atmospheric pressure. If Triton's internal heat flow is concentrated in some areas, as is likely, local effects such as enhanced sublimation with subsequent modification of albedo could be quite large. Furthermore, indications of recent global albedo change on Triton suggest that Triton's surface temperature and pressure may not now be in steady state, further suggesting that atmospheric pressure on Triton was as much as ten times higher in the recent past.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 251; 1465-146
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  • 49
    Publication Date: 2011-08-19
    Description: Model spectra have been constructed for the CH4 lines of the polar regions of Jupiter in such as way as to encompass the hydrogen pressure-induced opacity and haze layers revealed by high-resolution spectroscopy. Comparisons between observation and model spectra indicate that, for optically thin haze models, the polar haze is primarily located between the 70 and 5 mbar pressure levels; for opaque haze models, the top of the haze layers lies in the vicinity of the 15-mbar level. It is concluded that the polar haze is widely distributed over both polar regions and exhibits no strong correlation with auroral activities.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 91; 145-153
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  • 50
    Publication Date: 2011-08-19
    Description: Since the vapor phase composition of Titan's methane-nitrogen lower atmosphere is uniquely determined as a function of the Gibbs phase rule, these data are presently computed via integration of the Gibbs-Duhem equation. The thermodynamic consistency of published measurements and calculations of the vapor phase composition is then examined, and the saturated mole fraction of gaseous methane is computed as a function of altitude up to the 700-mbar level. The mole fraction is found to lie approximately halfway between that computed from Raoult's law, for a gas in equilibrium with an ideal solution of liquid nitrogen and methane, and that for a gas in equilibrium with pure liquid methane.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 91; 112-124
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  • 51
    Publication Date: 2011-08-19
    Description: Complete polarimetric signatures of a layer of random, nonspherical discrete scatterers overlying a homogeneous half space are studied with the first- and second-order solutions of the vector radiative transfer theory. Some of the salient features of the numerical results are as follows: (1) the inclusion of the nondiagonal extinction matrix in the vector radiative transfer theory accounts for an appreciable phase difference between vv and hh polarizations, particularly for aligned scatterers; (2) the ensemble-averaged scattered Stokes vector is generally partially polarized, with the degree of polarization less than unity; (3) there generally exists a pedestal in the copolarization return when plotted as a function of ellipticity and orientation angles, which may be due to heterogeneity of scattering objects and/or multiple scattering effects; and (4) multiple scattering effects generally enhance the pedestal in copolarization return, decrease the degree of polarization, affect phase difference, and also enhance the depolarization return.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: IEEE Transactions on Geoscience and Remote Sensing (ISSN 0196-2892); 29; 242-253
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  • 52
    Publication Date: 2011-08-19
    Description: Exospheric temperatures, T(ex), inferred from in situ measurements of neutral densities by the Pioneer Venus Orbiter have been analyzed to examine any possible dependence on solar wind dynamic pressure, P(sw). No linear relationship was found between P(sw) and T(ex). However, on one occasion when P(sw) was unusually high for a prolonged period, an unmistakable temperature enhancement was observed. Minor enhancement of T(ex) were also observed in few other cases, with sustained but moderately high P(sw).
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 7901-790
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  • 53
    Publication Date: 2011-08-19
    Description: A 0.3 - 0.6 micron UV-visible spectrophotometer and a 5 - 50 micron radiometer in the KRFM experiment on Phobos 2 measured two groundtracks in the equatorial region of Phobos. Preliminary results indicate that three surface units can be recognized on the basis of differing UV-visible spectral reflectance properties. One of the units is most comparable spectrally to optically darkened mafic material, and a second is comparable either to anhydrous carbonaceous chondrite or to blackened mafic material. Spectral properties of the third unit do not resemble those of known meteorite types. Brightness temperatures measured by the radiometer are consistent with a typical surface thermal inertia of 1 - 3 x 10 to the -3 cal/(sq cm deg s exp 1/2), as suggested by previous investigations, implying a lunar-like regolith texture. At least one area of possibly higher thermal inertia has been tentatively identified, where a large degraded crater is crossed by several grooves. These results indicate significant lateral heterogeneity in the optical and textural properties of Phobos' surface.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Planetary and Space Science (ISSN 0032-0633); 39; 311-326
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  • 54
    facet.materialart.
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    Publication Date: 2011-08-19
    Description: The modeling of the dynamics of particle collisions within planetary rings is discussed. Particles in the rings collide with one another because they have small random motions in addition to their orbital velocity. The orbital speed is roughly 10 km/s, while the random motions have an average speed of about a tenth of a millimeter per second. As a result, the particle collisions are very gentle. Numerical analysis and simulation of the ring dynamics, performed with the aid of a supercomputer, is outlined.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: American Scientist (ISSN 0003-0996); 79; 44-59
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  • 55
    Publication Date: 2011-08-19
    Description: The kinetic theory of planetary rings developed by Araki and Tremaine (1986) and Araki (1988) is extended and refined, with a focus on the implications of finite particle size: (1) nonlocal collisions and (2) finite filling factors. Consideration is given to the derivation of the equations for the local steady state, the low-optical-depth limit, and the steady state at finite filling factors (including the effects of collision inelasticity, spin degrees of freedom, and self-gravity). Numerical results are presented in extensive graphs and characterized in detail. The importance of distinguishing effects (1) and (2) at low optical depths is stressed, and the existence of vertical density profiles with layered structures at high filling factors is demonstrated.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 90; 139-171
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  • 56
    Publication Date: 2011-08-19
    Description: The surface of the Jovian satellite Europa is characterized on the basis of an analysis of ground photoelectric photometry at 470 and 550 nm and Voyager images. The data are presented in extensive tables and graphs and discussed in detail. At 550 nm, Europa has single-scattering albedo 0.964, opposition-effect amplitude 0.5, opposition-effect width 0.0016, double-lobed Henyey-Greenstein factors b = -0.429 and c = 0.113, and mean roughness angle 10 deg (much lower than on other solar-system objects). From the small roughness and the 96-percent porosity implied by the narrow opposition peak, it is concluded that the surface was formed mainly by endogenic processes. It is also noted that only one of three observational criteria for preferential ion bombardment of the trailing hemisphere are met in Europa.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 90; 30-42
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  • 57
    Publication Date: 2011-08-19
    Description: The surfaces of the Uranian satellites Ariel, Miranda, Oberon, Titania, and Umbriel are characterized on the basis of Voyager observations. Tables of spectrophotometric data and maps of normal reflectances, green/violet ratios, and possible geological formations are presented and discussed in detail. Variations in albedo are found to be associated with impact features, and it is inferred from color differences that the upper surface of Ariel contains a higher proportion of redder material (tentatively identified as accreted low-albedo meteoritic dust) than those of the other moons.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 90; 1-13
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  • 58
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    Publication Date: 2011-08-19
    Description: Novel approaches to the human exploration of Mars are considered with emphasis on a space suit design, extraterrestrial surface mobility, and water supply. A possible way of transporting personnel on the surface of Mars uses a suborbital rocket that will hop from one site to the next, refuelling each time it lands and giving the Martian explorers effective global mobility. Telepresence could be used to avoid limiting the people on Mars to a small exploration area as a result of a lack of transportation infrastructure. Drawings and photographs are included.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Spaceflight (ISSN 0038-6340); 33; 208-212
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  • 59
    Publication Date: 2011-08-19
    Description: A new type of meteoritic material, intermediate in size between meteorites and interplanetary dust particles (IDPs), is described. Melting and filtering of about 100 tons of blue ice near Cap Prudhomme, Antarctica, yielded 7500 or more irregular, friable particles and about 1500 melted spherules, about 100 microns in size, both showing a 'chondritic' composition suggestive of an extraterrestrial origin. Analyzed irregular particles appear to be unmelted and have similarities with the fine-grained matrix of primitive carbonaceous chondrites, but are extremely diverse in composition. Isotopic analysis of trapped neon confirms an extraterrestrial origin for 16 of 47 irregular particles and 2 of 19 spherules studied and strongly suggests that they were exposed in space as micrometeoroids. These large Antarctic micrometeorites constitute a new family, or at least a new population, of solar system objects, in a mass range corresponding to the bulk of extraterrestrial material accreted by the earth today.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 351; 44-47
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  • 60
    Publication Date: 2011-08-19
    Description: Research throughout the Caribbean suggests that the geophysical anomalies in the Yucatan first noted by Penfield and Camargo (1981) and called the Chicxulub crater could be the site of the impact purported to have caused the K/T extinctions. A semicircular ring of sink holes, known locally as cenotes, which correlates with the geophysical anomalies has been identified, and it is argued that the origin of the cenote ring is related to postimpact subsidence of the Chicxulub crater rim. If there is indeed a crater, the region within the cenote ring corresponds to its floor and the crater rim diameter is probably larger than 200 km. If confirmed as a site of impact, the Chicxulub crater would be the largest terrestrial impact crater known, which is consistent with the uniqueness of the K/T global catastrophe.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 351; 105
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  • 61
    Publication Date: 2011-08-19
    Description: An evaluation of the polarization signatures obtained from the four Stokes parameters is reported for the atmosphere and a soybean canopy. The polarimeter design and operation are set forth, and the Stokes parameters' relationships are discussed. The canopy polarization was different from the sky at azimuths of 90 and 270 degrees, demonstrating a response that reflecting the sky polarization signatures across a plane parallel to the polarization axis and passing through a phase angle of about 90 degrees would produce. Classical behavior in terms of electromagnetic theory was found in the fourth Stokes parameter of the canopy which was obtained in the principal plane. Only the third Stokes parameter is demonstrated to be unambiguously affected in a comparison of sky polarization signatures and aerosol optical densities. The similarity between the sky at azimuth 180 degrees and the soybean canopy data at the principal plane is interesting considering the disparity of the subjects.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 12; 1087-109
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  • 62
    Publication Date: 2011-08-19
    Description: Measurements of radar backscatter from an artificial tree were made in the laboratory at 6 and 10 GHz at horizontal incidence. The system had a resolution cylinder 18 cm in diameter and 11 cm long, so about half of the tree (30.5 cm high) was within the beam. The mean returned power from the target with leaves was always higher than that from the target without leaves, as expected. The signal faded with an exponential distribution when the artificial tree was rotated about its trunk, with no angular trend apparent. When the leaves were present, tilted polarizations gave results favoring an angle corresponding with that of the branches. When leaves were absent, the trunk of the tree dominated the radar backscatter at all polarizations.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: International Journal of Remote Sensing (ISSN 0143-1161); 12; 401-417
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  • 63
    Publication Date: 2011-08-19
    Description: The latest Voyager observations have shown large zonal velocities in Neptune's atmosphere, with some indication of alternating jets. Similar wind velocities have also been observed on Venus and are characteristic of planetary atmospheres in general, which is remarkable considering that the available solar or internal heating varies by more than a factor of 1000. A simplified model of the planetary circulation which provides some qualitative understanding is discussed. The basic assumption is that the source driving the circulation is also generating the dissipating eddies which are simulated by diffusion. Thus, the magnitude and structure of the zonal circulation are independent both of the source and the dissipation rate. The zonal velocities are related to the speed of sound and are of comparable magnitude in different atmospheres; although the available heating varies by a large factor, and the planetary parameters vary over a wide range. The alternating jets are described by a convective eigenmode which develops when energy transport out of the planetary interior is important, as is the case on Jupiter, Neptune, and Saturn.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astrophysical Journal, Part 1 (ISSN 0004-637X); 367; 361-366
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  • 64
    Publication Date: 2011-08-19
    Description: Trace element analyses of the phosphates minerals in stony-iron pallasite meteorites are used here to investigate the magmatic history of the silicate portions of pallasites. In Eagle Station and seven other pallasites, the phosphates have relatively low concentrations of REEs and are strongly enriched in heavy relative to light REE. These patterns are consistent with formation of phosphate by subsolidus reactions between metal and silicate, in which phosphate inherits the REE pattern of olivine. In Springwater and Santa Rosalia, calcium-rich phosphates have higher concentrations of REE, are enriched in light relative to heavy REE, and have negative europium anomalies. These patterns are consistent with crystallization of phosphate from a europium-depleted chondritic liquid. This is unlikely to have happened near the base of the differentiating parent-body mantle; it suggests that some pallasites may come from regions of their parent bodies much nearer the surface than the core-mantle boundary.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 353; 637-640
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  • 65
    Publication Date: 2011-08-19
    Description: An 8-b quantization scheme to reduce the data volume for single-look complex scattering matrix data measured by polarimetric imaging radar systems is described. The scattering matrices are not symmetrized before compression, thereby retaining information about background noise and system effects. The data volume is reduced by a factor of 3.2. It is shown, with measured data, that the signal to quantization noise ratio for the compression scheme is more than 35 dB for the cross-polarized channels, and more than 45 dB for the copolarized channels.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: IEEE Transactions on Geoscience and Remote Sensing (ISSN 0196-2892); 29; 784-786
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  • 66
    Publication Date: 2011-08-19
    Description: The presence of acetylene has been confirmed for some time in the atmospheres of the outer planets Jupiter, Saturn, Neptune, and Saturn's satellite Titan. For these atmospheres, the determination of C2H2 abundances using its strong nu5 fundamental requires laboratory line position and intensity measurements. The 1-m Fourier transform spectrometer at McMath solar telescope of Kitt Peak National Observatory was used to measure C2H2 at an unapodized spectral resolution of 0.0025/cm. Synthetic spectra are generated by convolving a Voigt line shape with an instrument function and varying intensity parameters by means of a nonlinear least squares technique. Intensities of 37 nu5 lines spanning P18 through R20 were measured using 0.123 torr of gas in a 1-cm cell. A Herman-Wallis intensity correction parameter of 1.3(4) x 10 to the -3rd has been derived using a least squares linear fit.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 17
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  • 67
    Publication Date: 2011-08-19
    Description: The present simulation of 1100-1400/cm region emissions ascribable to (C-12)H4, (C-13)H4, and CH3D, as seen by earth observers from a 4-km altitude, conclusively show that the polar hot-spots and other midlatitude features of broadband observations are stratospheric effects. Although signal enhancement in the broadband observations is obtained at increased Doppler shifts and zenith angles approaching zero, the magnitude in the former case is a function of stratospheric temperature.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 93; 174-178
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  • 68
    Publication Date: 2011-08-19
    Description: Complete solar phase curves of the Ganymede and Callisto leading and trailing hemispheres, which have been obtained by reducing Voyager imaging observations and combining them with ground-based telescopic data, are presently fit to scattering models in order to derive hemispherical values of the single scattering albedo, the single particle phase function (SPPF), the compaction state (CS) of the optically active portion of the regolith, and the mean slope angle of macroscopic features. While Callisto's leading side is composed of particles that are more strongly backscattering than the trailing side, no hemispheric differences are found in the CS, surface roughness, or SPPF.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 92; 312-323
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  • 69
    Publication Date: 2011-08-19
    Description: Asteroid spectral measurements are presently approached via comparisons with reflectance spectra from 60 powdered meteorite samples representing 50 different meteorites. While the powdered meteorites have undergone alteration by exposure to water vapor and by hydrocarbon contamination characterized by absorption bands near 3.45 microns, they retain various other spectral features which render them useful for identification. While these features can be used independently to ascertain mineralogy and meteorite type, the use of the entire spectrum in a digital search library is preferred for successful identification.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Icarus (ISSN 0019-1035); 92; 280-297
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  • 70
    Publication Date: 2011-08-19
    Description: This paper reevaluates Pioneer Venus probe data which show the presence of waves in Venus's middle and upper atmosphere. The data are extended to 138 km. Uncertainties in the temperature are typically about 0.1 times amplitude, supporting the reliability of large-amplitude oscillations approaching 40 K at 120 km. Growth rates above 100 km follow approximately the inverse square root of density and 'saturation' occurs. The waves then break at the 120 km level, providing a source for the 'friction' required in models to match the observed day-night temperature contrast in the lower thermosphere. The data correlated to an unexpected degree with temperatures from the Pioneer Venus orbiter atmospheric drag experiment. The observations lead to the suggestion that the thermospheric waves are solar-fixed, induced either by the major subsidence across the termination or as continuation upward of waves in the middle atmosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 11
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  • 71
    Publication Date: 2011-08-19
    Description: The coherent backscatter model is investigated experimentally by means of an analog to examine the nature of the radar reflectivity of icy satellites. The laboratory analog involves the examination of He-Ne laser light with a wavelength of 0.633 microns reflected from 0.497-micron polystyrene beads suspended in water. A photomultiplier and a polarizing filter are employed to observe the radar at phase angles greater than zero which are extrapolated to infer observation at zero phase angle. The polarization angles measured at optical frequencies are found to be equivalent to those observed in the radar data. The results suggest that the regoliths of the icy satellites consist of matrices of small complex refractive indices which contain scatterers separated by distances of the order of a wavelength. The experiment explains the high reflectivity of Jupiter's icy satellites which results in the observation of narrow opposition-effects peaks at optical frequencies.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 352; 46
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  • 72
    Publication Date: 2011-08-19
    Description: Careful inspection of many images taken by the Voyager spacecraft reveals the presence within the Encke gap of Saturn's eighteenth satellite. Its existence had been inferred from gravitational disturbances seen in Voyager data, and it falls close to the predicted orbit, its shepherding effect is responsible for keeping the Encke gap open, and it may also be the progenitor of a narrow ringlet within the gap.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 351; 709-713
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  • 73
    Publication Date: 2011-08-19
    Description: Electron impact excitation of the b 1Pi(u) state in N2 plays a prominent role in the dissociation of the molecule and thus in the production of atomic nitrogen in planetary atmospheres. Electron impact excitation cross sections combined with electron-impact-induced fluorescence measurements can yield the corresponding dissociation cross sections. Serious discrepancies exist among excitation cross sections reported in the literature. To clarify the situation, these cross sections were measured at two impact energies using electron energy loss spectroscopy. The new results are in agreement with recent values deduced from optical measurements and fall midway between previous results which are too high or low by factors of 2.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 17
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  • 74
    Publication Date: 2011-08-19
    Description: Galileo's instruments obtained a broad range of planetary measurements during the spacecraft's Venus encounter on February 10, 1990. The instrumentation brought to bear encompassed UV spectra, limb haze studies, and particles-and-fields experiments. These data, in conjunction with ground-based observations conducted during the encounter, have yielded accurate information on the Venus plasma environment, cloud patterns, and the possibility of interpreting certain impulsive events as lightning.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 253; 1516-151
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  • 75
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    Publication Date: 2011-08-19
    Description: This paper reviews the role of terrestrial hydrology in determining the coupling between the surface and atmosphere. Present experience with interactive numerical simulation is discussed and approaches to the inclusion of land hydrology in global climate models ae considered. At present, a wide range of answers as to expected changes in surface hydrology is given by nominally similar models. Studies of the effects of tropical deforestation and global warming illustrate this point.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Tellus, Series A-B: Special Issue (ISSN 0280-6495); 43A-B; 176-181
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  • 76
    Publication Date: 2011-08-19
    Description: The conservation equations of plasma dynamics in the upper ionosphere of Venus have been solved by using a spectral method in the horizontal and finite differencing in the vertical direction. The effect of varying the ionopause height on the computed nightside ion densities is investigated. These ion densities show a sharp decrease as the ionopause altitude is reduced to 300 km. The effect of viscous forces on the horizontal plasma flow is investigated for a wide range of values of the coefficient of viscosity. The Reynolds numbers characteristics of the flow are calculated and the conditions for the onset of turbulence discussed. It is found that the Reynolds number can be large (greater than 1000) in the subsolar region for a coefficient of viscosity of up to 1.6 x 10 to the -10th g/cm s. The influence of magnetic fields on viscosity is also discussed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Indian Journal of Radio and Space Physics (ISSN 0367-8393); 20; 150-156
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  • 77
    Publication Date: 2011-08-19
    Description: Results of two experiments performed onboard the Phobos spacecraft are presented: spectrophotometry in the 300-600 nm range and thermal radiometry, i.e., intrinsic thermal emission in the 6-50 micron range. The thermophysical characteristics of the Phobos regolith are indicated by a thermal inertia coefficient which is similar to that of the moon. The reflectivity of the regolith is inhomogeneous in the region investigated and depends mostly on the relief features, primarily craters and their age. The expected similarity of the reflection spectra with those of carbonacenous chondrites was not confirmed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Kosmicheskie Issledovaniia (ISSN 0023-4206); 29; 621-640
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  • 78
    Publication Date: 2011-08-19
    Description: Partition coefficients for Au, Ni, P, and Ge between solid Fe-Ni metal and sulfur-bearing metallic liquids have been measured at 7, 27 and 80 kbar. These are the only such data for Au, P, and Ge at high pressure. Comparison of the present partitioning results to those obtained at 1 bar indicate that only the 80-kbar Ge data differ significantly from the 1-bar experiments. Thus, many low-pressure partitioning experiments in the Fe-Ni-S-P system may have applicability to the greater portion of the earth's upper mantle or, alternatively, the entire mantle of Mars.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Earth and Planetary Science Letters (ISSN 0012-821X); 105; 1-3,; 127-133
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  • 79
    Publication Date: 2011-08-19
    Description: Thermal stress histories of the Saturnian and Uranian satellites are investigated. To this end, the thermal evolution of an icy satellite subjected to accretional and radiogenic heating, thermal conduction, and solid-state convection is modeled, and changes in the internal stress that occur during satellite evolution are examined. Results show that internal temperature changes that occur during normal evolution of many of the satellites of Saturn and Uranus can be expected to generate large extensional stresses in the satellites' outer regions. These stresses arise from three sources: (1) radiogenic warming, causing thermal expansion of materials in the satellite's deep interior; (2) radiogenic warming in larger satellites that can induce a phase transition from ice II to ice I and to produce a volume increase in the deep interior; and (3) accretional heating depositing heat in the satellite'e outer regions.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 15
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  • 80
    Publication Date: 2011-08-19
    Description: Results are presented on measurements of crater depths and other morphological parameters (such as central peak and terrace frequency) of fresh craters on Ganymede and Callisto, two geophysically very similar but geologically divergent large icy satellites of Jupiter. These data were used to investigate the crater mechanics on icy satellites and the intersatellite crater scaling and crustal properties. The morphological transition diameters of and complex crater depths on Ganymede and Callisto were found to be similar, indicating that the crusts of both satellites are dominated by water ice with only a minor rocky component.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 15
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  • 81
    Publication Date: 2011-08-19
    Description: New information is presented on the structural and stratigraphic evolution of the Tharsis region of Mars, along with a lithospheric deformation model that can account for the observations. According to this model, the lithosphere beneath Tharsis consists of a thin elastic crustal cap on the rise, which is mechanically detached from the strong upper mantle by a volcanically thickened, hot, weak lower crust; these layers merge into a single cooler strong lithospheric layer around the edges of the rise. It is suggested that the nonuniform distribution of tectonic features and strain around Tharsis is due to the concentration of regional stresses near weaker volcanotectonic centers.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 15
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  • 82
    Publication Date: 2011-08-19
    Description: Numerical simulations of Martian neutron leakage flux spectra are made in order to explore the detectability of magnesium and calcium carbonate deposits using neutron spectroscopic techniques from orbit. The primary signature of such deposits is found to be an enhanced thermal amplitude. Although this enhancement is weakened by: (1) partial burial beneath an aeolian regolith blanket; (2) admixture with regolith on a microscopic (centimeter) or macroscopic (tens of centimeters) scale; and (3) reduction in the areal size of the deposit, near-surface stratigraphies of carbonates hypothesized by some authors as possible on Mars are still detectable by simple neutron sensors from orbit. However, the large variations in the magnitude of the thermal neutron enhancements caused by different carbonate deposit configurations found in this study require a combined gamma ray and neutron analysis for their unique specification.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 15
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  • 83
    Publication Date: 2011-08-19
    Description: A 10 x 13-km area in Quetico Provincial Park, Canada has been studied using a digital elevation model to separate different drainage classes and to examine the influence of site factors and lithology on vegetation. Landsat Thematic Mapper data have been classified into six forest classes of varying deciduous-coniferous cover through nPDF, a procedure based on probability density functions. It is shown that forests growing on mafic lithologies are enriched in deciduous species, compared to those growing on granites. Of the forest classes found on mafics, the highest coniferous component was on north facing slopes, and the highest deciduous component on south facing slopes. Granites showed no substantial variation between site classes. The digital elevation derived site data is considered to be an important tool in geobotanical investigations.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Photogrammetric Engineering and Remote Sensing (ISSN 0099-1112); 57; 1179-118
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  • 84
    Publication Date: 2011-08-19
    Description: Remotely acquired multispectral data are used to improve landslide hazard assessments at all scales of investigation. A vegetation map produced from automated interpretation of TM data is used in a GIS context to explore the effect of vegetation type on debris flow occurrence in preparation for inclusion in debris flow hazard modeling. Spectral vegetation indices map spatial patterns of grass senescence which are found to be correlated with soil thickness variations on hillslopes. Grassland senescence is delayed over deeper, wetter soils that are likely debris flow source areas. Prediction of actual soil depths using vegetation indices may be possible up to some limiting depth greater than the grass rooting zone. On forested earthflows, the slow slide movement disrupts the overhead timber canopy, exposes understory vegetation and soils, and alters site spectral characteristics. Both spectral and textural measures from broad band multispectral data are successful at detecting an earthflow within an undisturbed old-growth forest.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Photogrammetric Engineering and Remote Sensing (ISSN 0099-1112); 57; 1185-119
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  • 85
    Publication Date: 2011-08-19
    Description: Data from polar-orbiting meteorological satellites have been used to determine the extent of the Sahara Desert and to document its interannual variation from 1980 to 1990. The Sahara Desert ranged from 8,633,000 square kilometers in 1980 to 9,982,000 square kilometers in 1984. The greatest annual north-south latitudinal movement of the southern Saharan boundary was 110 kilometers from 1984 to 1985 and resulted in a decrease in desert area of 724,000 square kilometers.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Science (ISSN 0036-8075); 253; 299-301
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  • 86
    Publication Date: 2011-08-19
    Description: The Martian atmosphere has a high X-129/Xe-132 ratio compared to the Martian mantle. As Xe-129 is the daughter product of the extinct nuclide I-129, a means of fractionating iodine from xenon early in Martian history appears necessary to account for the X-129/Xe-132 ratios of its known reservoirs. A model is presented here to account for the Marian xenon data which relies on the very different solubilities of xenon and iodine in water to fractionate them after outgassing. Atmospheric xenon is lost by impact erosion during heavy bombardment, followed by release of Xe-129 produced from I-129 decay in the crust.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 352; 697-699
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  • 87
    Publication Date: 2011-08-19
    Description: The 225.9 GHz line of HDO has been detected in absorption in the atmosphere of Venus, with the 30-m IRAM antenna. This measurement gives information regarding the vertical distributions of HDO, and thus H2O, in this planet. The observations are consistent with an H2O vertical distribution strongly depleted by saturation at an altitude of 95 km, and, assuming a D/H enrichment of 120 with respect to the terrestrial value, with a mixing ratio of 3.5 (+ or - 2.0) ppm in the range 65-95 km.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Astronomy and Astrophysics (ISSN 0004-6361); 246; 1, Ju
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  • 88
    Publication Date: 2011-08-19
    Description: Acquisition of ground truth data for use in microwave interaction modeling requires measurement of surface roughness sampled at intervals comparable to a fraction of the microwave wavelength and extensive enough to adequately represent the statistics of a surface unit. Sub-centimetric measurement accuracy is thus required over large areas, and existing techniques are usually inadequate. A technique is discussed for acquiring the necessary photogrammetric data using twin film cameras mounted on a helicopter. In an attempt to eliminate tedious data reduction, an automated technique was applied to the helicopter photographs, and results were compared to those produced by conventional stereogrammetry. Derived root-mean-square (RMS) roughness for the same stereo-pair was 7.5 cm for the automated technique versus 6.5 cm for the manual method. The principal source of error is probably due to vegetation in the scene, which affects the automated technique but is ignored by a human operator.
    Keywords: EARTH RESOURCES AND REMOTE SENSING
    Type: Photogrammetric Engineering and Remote Sensing (ISSN 0099-1112); 57; 1075-107
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  • 89
    Publication Date: 2011-08-19
    Description: The behavior of the Venus nightside ionosphere at solar maximum and solar minimum is discussed based on Pioneer Venus radio occultation measurements. Although some solar maximum measurements are similar to those observed at minimum, which have an average peak density of about 7000/cu cm, others show much higher peak densities, reaching values of about 40,000/cu cm. These elevated peak densities also occur at higher altitudes. The integrated electron column densities for these measurements indicate the presence of substantial ionization above the main peak. The magnitudes of both the peak density and the integrated content above the peak are anticorrelated with the solar wind dynamic pressure, indicating that these enhancements during solar maximum are due to transterminator transport of O(+) ions from the dayside. The resulting ionization peak can be many times the concentration produced by energetic electron fluxes impacting the neutral atmosphere on the nightside.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 11
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  • 90
    Publication Date: 2011-08-19
    Description: The results are reported of a search during 1988 and 1990 for optical pulses from lightning on the Venus nightside using the star sensor aboard the Pioneer Venus Orbiter. No optical evidence for lightning activity is found. These searches covered a much larger latitude range than any previous search. The results show that the Beta and Phoebe Regio areas previously identified by Russell et al. (1988) as areas with high rates of lightning activity were not active during the two seasons of the present observations. The results imply that the global flash rate and energy dissipation rate derived by Krasnopol'sky (1983) from observations of a single storm are too high. Experimental measurements performed to determine the amount of scattering occurring in the star scanner optics indicate that a previously determined upper bound to lightning activity is too low.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 11
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  • 91
    Publication Date: 2011-08-19
    Description: A remarkable feature of the ionosphere of Venus is the presence of nightward supersonic flows at high altitude near the terminator. In this paper it is shown that the relatively high pressure dayside plasma wells up slowly, and at high altitude it is accelerated horizontally through a relatively constricted region near the terminator toward the low-density nightside. In effect, the plasma flows through a 'nozzle' that is first converging, then diverging, permitting the transition to supersonic flow. The model plasma accelerates to supersonic speeds, reaching sonic speed just behind the terminator. The ion transport rates are sufficient to produce and maintain the nightside ionosphere.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 11
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  • 92
    Publication Date: 2011-08-19
    Description: It is reported here that interstellar graphite and SiC grains recovered from the Murchison CM2 chondritic meteorite have large abundances of Mg-26 from the decay of extinct Al-26. The deduced initial Al-26/Al-27 ratios range up to 0.06 in graphite and 0.2 in SiC. This is 1200 to 4000 times the maximum values found in refractory inclusions in primitive meteorites. All proposed stellar sources of carbonaceous dust also produced Al-26, but the highest Al-26/Al-27 ratios found in these grains seem to rule out Wolf-Rayet stars and supernovae. The aluminum abundance correlates with that of nitrogen, suggesting that the aluminum condensed as aluminum nitride.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 349; 51-54
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  • 93
    Publication Date: 2011-08-19
    Description: Pioneer Venus orbiter (PVO) gravity profiles over Aphrodite Terra are compared with profiles predicted from models of thermal isostasy, mantle convection, and Airy compensation. Topography profiles across Aphrodite are compared to model spreading-ridge profiles in order to further assess this model. Airy compensation depths and convection-layer thicknesses are greater under eastern Aphrodite than western Aphrodite. Compensation depths in the east are greater than most estimates of lithospheric thickness, suggesting that this part of the ridge is dynamically supported. In parts of western Aphrodite, the spreading-ridge model gravity provides a better fit to the data than either Airy compensation or mantle convection. Best-fit spreading rates are between 0.3 and 1.6 cm/yr. Airy compensation and mantle convection cannot be distinguished in most places using only PVO data.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 301-315
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  • 94
    Publication Date: 2011-08-19
    Description: In laboratory simulations of the Venusian environment, rock and mineral 'target' surfaces struck by aeolian particles develop a thin layer of accretionary material derived from the particles' attrition debris. Accretion may be (in part) a manifestation of 'cold welding', a process well known in engineering, where bonding occurs between metals at a tribological interface. Accretion on geological materials was found to occur at all Venusian surface temperatures and for all types of materials tested. First-order variations in the amount deposited by particles are related to relative attrition susceptibilities. Second-order variations relate to properties of the particle-target interface. Variations in accretion volume are apparently independent of mineral chemistry and are only weakly dependent on crystallography. The results suggest that accretion should be a fairly universal phenomenon in areas of Venus subject to aeolian activity.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 1931-194
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  • 95
    Publication Date: 2011-08-19
    Description: Several types of volcanic units have been recognized on the icy Uranian satellites Miranda and Ariel. On Miranda, ridges characterized by crest grooves are up to 10 km wide and 500 m high. A continuous flat-topped flow band also 10 km wide and 500 m high forms the outer southern margin of Elsinore Corona, which appears to comprise coalesced flow bands and ridges. On Ariel, in addition to at least one ridge unit similar to those on Miranda, flood plains material has covered the floors of deep chasmata (grabens) and an irregular depression. Flows on both satellites are characterized by linear vent geometries and distinct topographic margins, which indicate extrusion of a relatively viscous material. The topography of the flows can be used to estimate flow viscosity or yield strength using a Bingham plastic model. Extrusion viscosity estimates, incorporating plausible volcanologically based emplacement time scales and a rigid crust correction, range from 10 MP to 1 GP (10 TP in the unlikely absence of a chilled crust). Viscosity estimates are dependent on the assumed emplacement time scale, however, and could be as high as 10 PP, if a solid-state-based time scale is assumed.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 1887-190
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  • 96
    Publication Date: 2011-08-19
    Description: Geomorphic and stratigraphic analysis of Alba Patera suggests a volcanic construct built by lavas with rheologic properties similar to basalts. A series of evolving eruptive styles is suggested by changes in morphology and inferred progressive reductions in flow volume with higher stratigraphic position. Alba Patera's volcanic history has been summarized into four main phases. The first is characterized by extensive flood like flows presumably erupted from fissures associated with the initial intrusion of magma into the region. The second phase is associated with the emplacement of pyroclastic rock, a more speculative interpretation. The third phase produced the voluminous tabular, crested, and undifferentiated flows, probably from a more centralized vent source. The fourth and last phase is marked the effusion of levee like flows and the collapse of the summit calderas and final graben formation.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Journal of Geophysical Research (ISSN 0148-0227); 96; 1907-193
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  • 97
    Publication Date: 2011-08-19
    Description: Data were obtained on the trace- and major-element compositions of 16 Antarctic abnormal eucrites, many of which exhibiting positive (but sometimes negative) Ce anomalies, positive Eu anomalies, and low abundances of the remainder of the REEs. The results of data analysis suggest that the unusual REE patterns of abnormal Antarctic eucrites arise from weathering effects generated in or on the Antarctic ice. The suggested scenario involves the formation of melt water and its equilibration with the atmosphere, promoting the dissolution of REE-rich phosphates and the oxidation of Ce. As a result, tetravalent Ce is fractionated from the trivalent REE in solution.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 55; 77-87
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  • 98
    Publication Date: 2011-08-19
    Description: Results are presented on the mineralogy, chemistry, and origin of white efflorescences on the surface of Lewis Cliff (Antarctica) 85320 (H5) chondrite (LEW 85320). Particular attention is given to determining the sources of the cations and anions of the evaporite, in order to establish the relative importance of the meteoritic element distribution and terrestrial contamination in the evaporite formation during the weathering process. The data on Na, K, Ca, and Rb abundances in efflorescence from LEW 85320 suggest that cations in evaporite minerals on Antarctic meteorites are not the products of contamination by terrestrial (marine) salts. It is suggested that the Mg in efflorescence on LEW 85320 originated from weathering of meteoritic olivine.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Geochimica et Cosmochimica Acta (ISSN 0016-7037); 55; 67-76
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  • 99
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    Publication Date: 2011-08-19
    Description: The great storm now going on in the atmosphere of Saturn is discussed. Observational results are summarized, and possible explanations for the storm's origin are addressed. The potential for ongoing observations to clarify the storm's causes is considered.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Nature (ISSN 0028-0836); 349; 21
    Format: text
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  • 100
    Publication Date: 2011-08-19
    Description: Eucrites and angrites are distinct types of basaltic meteorites whose origins are poorly known. Experiments in which samples of the Allende (CV3) carbonaceous chondrite were partially melted indicate that partial melts can resemble either eucrites or angrites, depending only on the oxygen fugacity. Melts are eucritic if this variable is below that of the iron-wuestite buffer or angritic if above it. With changing pressure, the graphite-oxygen redox reaction can produce oxygen fugacities that are above or below those of the iron-wuestite buffer. Therefore, a single, homogeneous, carbonaceous planetoid greater than 110 kilometers in radius could produce melts of drastically different composition, depending on the depth of melting.
    Keywords: LUNAR AND PLANETARY EXPLORATION
    Type: Science (ISSN 0036-8075); 252; 695-698
    Format: text
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