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  • 101
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    Inferring total canopy APAR from PAR bidirectional reflectances and vegetation indices in tallgrass prairie (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: The fraction of photosynthetically active radiation (PAR) absorbed by a vegetated canopy (APARc) or landscape (APARs) is a critical parameter in climate processes. A grassland study examined: 1) whether APARs can be estimated from PAR bidirectional exitance fractions; and 2) whether APARs is correlated with spectral vegetation indices (SVIs). Data were acquired with a high resolution continuous spectroradiometer at 4 sun angles on grassland sites. APARs was computed from the scattered surface PAR exitance fractions. The nadir APARs value was the most variable diurnally; it provided a good estimate of the average surface APARs at ~95 percent. APARc was best represented by exitance factors between 30-60* forward.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 749-751.
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  • 102
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    The NASA/JPL three-frequency polarimetric AIRSAR system (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: The NASA/Jet Propulsion Laboratory Airborne Synthetic Aperture Radar (JPL AIRSAR) system has now completed four flight campaigns. The authors describe the current state of this system and provide insight into how flight seasons are planned for this instrument. The data processors and data products are described. A table containing relevant system parameters is provided.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 649-651.
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  • 103
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    Monitoring of environmental conditions in the Alaskan forests using ERS-1 SAR data (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: Preliminary results from an analysis of the multitemporal radar backscatter signatures of tree species acquired by European Remote Sensing Satellite (ERS-1) synthetic aperture radar (SAR) data are presented. Significant changes in radar backscatter are detected. Correlation of these differences with ground truth observations indicate that these are due to changes in soil and liquid water content as a result of freeze/thaw events. C-band observations acquired by the NASA/Jet Propulsion Laboratory Airborne SAR (JPL AIRSAR) instrument demonstrate the potential of a C-band radar instrument to monitor drought/flood events. The potential of ERS-1 for monitoring phenologic changes in the forest and for classifying tree species is less promising.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 530-532.
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  • 104
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    An investigation of the relationship between tree water potential and dielectric constant (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: An experiment that has been performed to verify the relationship between the dielectric constant of several tree species and their respective water potentials is described. The water potential, xylem flow and dielectric properties of five tree species were continuously monitored while simultaneously manipulating canopy transpiration and water status. An analysis of the data recorded during these manipulations is presented. Results of this analysis demonstrate a clear coincidence of change in dielectric constant and water status. The implication of this relationship for the utilization of remotely sensed data to study canopy water relations is explored. Preliminary backscatter modeling results demonstrate that the changes in dielectric constant that occur as a result of changes in water status are significant enough to be observable with microwave radar.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 523-525.
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  • 105
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    Radiometric correction of SAR images of varying terrain heights (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: The advantages and disadvantages of three different approaches to solving the problem of the radiometric correction of synthetic aperture radar (SAR) images of varying terrain heights are presented. The first approach involves registration of a digital elevation model (DEM) of the terrain to the image, determination of the local elevation and incidence angles, and appropriate radiometric correction. The second approach uses a DEM generated from interferometric SAR data to derive the elevation and incidence angle maps. In the third approach, a monopulse technique is employed to determine the elevation angle only. The relative errors in radiometric correction between these approaches are assessed. Calibration errors are estimated using corner reflectors deployed within some of the scenes imaged by the Jet Propulsion Laboratory airborne SAR (JPL AIRSAR).
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 271-273.
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  • 106
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    Ground support for Space Shuttle earth observations by the NASA environment remote sensing analysis facility (ERSAF) (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: The functions and capabilities of the NASA Environment Remote Sensing Analysis Facility (ERSAF) located at the Johnson Space Center are described. ERSAF provides dedicated support to earth-observation activities and Earth-looking payloads conducted aboard the Space Shuttle. This support merges environmental satellite imagery with high-resolution film products and digital imagery acquired aboard the Space Shuttle. ERSAF utilizes several computer systems with specialized software to process and analyze environmental information as well as data acquired from the Space Shuttle. These computer systems and the image analysis capabilities are discussed.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 158-160.
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  • 107
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    Relative phase calibration of the NASA/DC-8 three-frequency polarimetric SAR system (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: Relative phase calibration of radar polarimetry data may be achieved by utilizing the phase information of the receiver calibration tone and knowledge of the antenna path differences among channels measured upon installation of the radar polarimeter. This calibration method does not require any assumptions on the scattering behavior of the scene. This method of phase calibration may be verified by examining the polarization signatures of calibration instruments such as the trihedral corner reflectors.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 104, 105.
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  • 108
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    ESTAR - A synthetic aperture microwave radiometer for measuring soil moisture (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: The measurement of soil moisture from space requires putting relatively large microwave antennas in orbit. Aperture synthesis, an interferometric technique for reducing the antenna aperture needed in space, offers the potential for a practical means of meeting these requirements. An aircraft prototype, electronically steered thinned array L-band radiometer (ESTAR), has been built to develop this concept and to demonstrate its suitability for the measurement of soil moisture. Recent flights over the Walnut Gulch Watershed in Arizona show good agreement with ground truth and with measurements with the Pushbroom Microwave Radiometer (PBMR).
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 483-485.
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  • 109
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    Topographic mapping from ERS-1 and SEASAT radar interferometry (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: A radar interferometric technique for topographic mapping of surfaces yields a high resolution, globally consistent approach to generation of digital elevation models. The technique is illustrated with maps generated from SEASAT and European Space Agency Remote Sensing Satellite (ERS-1) data. A SEASAT interferometric image of a forested area which includes some unvegetated lava flows is analyzed. An analysis of errors expected from application of the technique to maps generated from ERS-1 data is presented. An orbital scenario for a global mapping mission is outlined.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 387, 388.
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  • 110
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    Laser-beam power for lunar and space applications (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: Photovoltaic properties of GaAlAs/GaAs heteroface converters were measured using a 0.81-micron diode laser. Results indicate that the converters under consideration are promising devices for converting diode-laser radiation to electricity. Conversion efficiency as high as 45 percent has been obtained using GaAs devices, while Si converters of the SSF type give efficiencies up to 34.2 percent.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: ; : Conference on the
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  • 111
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    Multispectral thermal infrared mapping of the 1 October 1988 Kupaianaha flow field, Kilauea volcano, Hawaii (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: Multispectral thermal infrared radiance measurements of the Kupaianaha flow field were acquired with the NASA airborne Thermal Infrared Multispectral Scanner (TIMS) on the morning of 1 October 1988. The TIMS data were used to map both the temperature and emissivity of the surface of the flow field. The temperature map depicted the underground storage and transport of lava. The presence of molten lava in a tube or tumulus resulted in surface temperatures that were at least 10 C above ambient. The temperature map also clearly defined the boundaries of hydrothermal plumes which resulted from the entry of lava into the ocean. The emissivity map revealed the boundaries between individual flow units within the Kupaianaha field. Distinct spectral anomalies, indicative of silica-rich surface materials, were mapped near fumaroles and ocean entry sites. This apparent enrichment in silica may have resulted from an acid-induced leaching of cations from the surfaces of glassy flows.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: Bulletin of Volcanology (ISSN 0258-8988); p. 33-44.
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  • 112
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    The effect of topography on radar scattering from vegetated areas (1993)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: This paper shows how the radar scattering from vegetated areas is affected by the topography of the surface underneath the vegetation. It is shown, using a discrete scatterer model, that the dominant scattering mechanism may change drastically when the ground surface is tilted relative to the horizontal. In the case of a horizontal ground surface, total scattering may be dominated by scattering off the tree trunks, followed by a reflection off the ground surface. For a relatively small tilt in the ground surface (about 2 deg from horizontal), the ground-trunk interaction term may be replaced by scattering from the branches alone as the dominant scattering mechanism. We also show that the effect of the topography is more pronounced for scattering by longer wavelengths, and discuss the implications on algorithms designed to infer forest woody biomass and soil and vegetation moisture using polarimetric SAR data. The effect of the topography on the scattering behavior from forested areas is illustrated with images acquired by the NASA/JPL three-frequency polarimetric SAR over the Black Forest in Germany.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: IEEE Transactions on Geoscience and Remote Sensing (ISSN 0196-2892); 31; 1; p. 153-160.
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  • 113
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    Microwave soil moisture estimation in humid and semiarid watersheds (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Land surface hydrologic-atmospheric interactions in humid and semi-arid watersheds were investigated. Active and passive microwave sensors were used to estimate the spatial and temporal distribution of soil moisture at the catchment scale in four areas. Results are presented and discussed. The eventual use of this information in the analysis and prediction of associated hydrologic processes is examined.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: Advances in Space Research (ISSN 0273-1177); 13; 5; p. 115-118.
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  • 114
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    Regional studies of the land surface using space-based means (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Regional ecological studies are considered in the context of the global change problem. The Kursk-91 international experiment is used to illustrate applications of remote sensing data and data bases of field experiments for assessment of parameters of the state of the soil and vegetative cover and subsequent study of biospheric stability on the basis of regular satellite observations.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: Issledovanie Zemli iz Kosmosa (ISSN 0205-9614); 2Apr; p. 63-75.
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  • 115
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    Astronaut observations of the Persian (Arabian) Gulf during STS-45 (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: As a result of the 1991 Persian Gulf war, between mid-January and June 1991, the Persian Gulf was contaminated with an estimated 4 to 6 million barrels of crude oil, released directly into the Gulf from refinement facilities, transhipment terminals, and moored tankers along the coast of Kuwait, and precipitated from oil fire smoke plumes. To assess the environmental impact of the oil, an international team of marine scientists representing 14 nations was assembled under the auspices of the United Nations International Oceanic Commission and the Regional Organization for Protection of the Marine Environment to conduct detailed surveys of the Persian Gulf, the Strait of Hormuz, and the Gulf of Oman, including hydrographic, chemical, and biological measurements. To supplement the field surveys and to serve as an aid in data interpretation, astronauts aboard the Space Shuttle Atlantis photographed water features and coastal habitats in the Persian Gulf during mission STS-45 (24 March to 02 April 1992). The astronauts collected 111 hand-held, color photographs of the Gulf (72 70-mm photographs and 39 5-inch photographs) from an altitude of 296 km (160 n.mi.). The photographs reveal distributions in water turbidity associated with outflow from the Shatt-al-Arab and water circulation along the entire coast of Iran and the Strait of Hormuz, coastal wetlands and shallow-water habitats, and sticks appearing in the sunglint pattern, which appear to be oil.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: Geocarto International (ISSN 1010-6049); 7; 4; p. 59-68.
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  • 116
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    Mutual coupling between parallel columns of periodic slots in a ground plane surrounded by dielectric slabs (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: Arrays of slots with arbitrary orientation in a conducting plane which are infinitely periodic in one dimension and finitely periodic in another dimension are considered. The perfect conducting plane extends infinitely and is bounded on each side by dielectric slabs of finite thickness and infinite extent. Single columns of slots are represented by equivalent magnetic scattering currents, which are solved for via the moment method. The mutual coupling (admittance) between slot columns in the presence of the stratified media is found by the array scanning method (ASM), which expresses the admittance as the average of the scan admittance of an artificially constructed doubly infinite array of slots over all real scan angles. The technique avoids the use of Sommerfeld integrals, but still gives rise to singularities at scan angles corresponding to the resonant excitation of surface waves. An analytical approximation is made to remove these surface wave singularities, thus making numerical implementation of the method practical. The method is quite general and may be extended to thin slot elements of arbitrary shape and orientation.
    Schlagwort(e): COMMUNICATIONS AND RADAR
    Materialart: IEEE Transactions on Antennas and Propagation (ISSN 0018-926X); 40; 11; p. 1324-1335.
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  • 117
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    Earth observations during Space Shuttle mission STS-45 Mission to Planet Earth - March 24-April 2, 1992 (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: A description is presented of the activities and results of the Space Shuttle mission STS-45, known as the Mission to Planet Earth. Observations of Mount St. Helens, Manila Bay and Mt. Pinatubo, the Great Salt Lake, the Aral Sea, and the Siberian cities of Troitsk and Kuybyshev are examined. The geological features and effects of human activity seen in photographs of these areas are pointed out.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: Geocarto International (ISSN 1010-6049); 7; 4; p. 69-80.
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  • 118
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    Evaluation of frequency-selective reflector antenna systems (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The performance of a four-frequency (S/X/Ku/Ku bands) frequency-selective surface (FSS) with double-ring elements (the type of geometry particularly well suited for the circular polarization requirement of the NASA's Cassini project) is evaluated for a planar and a curved FSS subreflector in a dual reflector antenna system. Good agreement is obtained between the calculated and measured data for the planar FSS model. The FSS effects in a four-frequency Cassegrain reflector antenna were accurately evaluated by taking into account the surface curvature and the FSS subreflector's transmitted/reflected field variation as functions of the polarization and the incident angles with respect to the local coordinates.
    Schlagwort(e): COMMUNICATIONS AND RADAR
    Materialart: Microwave and Optical Technology Letters (ISSN 0895-2477); 6; 3; p. 175-179.
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  • 119
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    Spectral-domain moment-method analysis of coplanar microstrip parasitic subarrays (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Basic characteristics of several configurations of coplanar microstrip parasitic subarrays consisting of one fed patch and two or more parasitic patches were investigated by means of a spectral-domain full-wave analysis and the moment method analysis. Results are presented for radiating- and nonradiating edge-coupled three-element linear subarrays and for a five-patch cross. A comparison of the theoretical input impedance results obtained by the analysis of a three-element linear array showed a reasonable agreement between computed and measured R and X values.
    Schlagwort(e): COMMUNICATIONS AND RADAR
    Materialart: Microwave and Optical Technology Letters (ISSN 0895-2477); 6; 3; p. 157-163.
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  • 120
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    Benchmark radar targets for the validation of computational electromagnetics programs (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Results are presented of a set of computational electromagnetics validation measurements referring to three-dimensional perfectly conducting smooth targets, performed for the Electromagnetic Code Consortium. Plots are presented for both the low- and high-frequency measurements of the NASA almond, an ogive, a double ogive, a cone-sphere, and a cone-sphere with a gap.
    Schlagwort(e): COMMUNICATIONS AND RADAR
    Materialart: IEEE Antennas and Propagation Magazine (ISSN 1045-9243); 35; 1; p. 84-89.
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  • 121
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    I-BIEM calculations of the frequency dispersion and ac current distribution at disk and ring-disk electrodes (1991)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: The Iterative Boundary Integral Equation Method (I-BIEM) has been applied to the problem of frequency dispersion at a disk electrode in a finite geometry. The I-BIEM permits the direct evaluation of the AC potential (a complex variable) using complex boundary conditions. The point spacing was made highly nonuniform, to give extremely high resolution in those regions where the variables change most rapidly, i.e., in the vicinity of the edge of the disk. Results are analyzed with respect to IR correction, equipotential surfaces, and reference electrode placement. The current distribution is also examined for a ring-disk configuration, with the ring and the disk at the same AC potential. It is shown that the apparent impedance of the disk is inductive at higher frequencies. The results are compared to analytic calculations from the literature, and usually agree to better than 0.001 percent.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: In: Modeling of batteries and fuel cells; Proceedings of the Symposium, Phoenix, AZ, Oct. 13-19, 1991 (A93-34244 13-25); p. 324-350.
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  • 122
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    Remote sensing of submerged vegetation canopies for biomass estimation (1993)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: The visible bands of the Landsat Thematic Mapper (TM) sensor were used in an empirical assessment of seagrass biomass on shallow banks near Lee Stocking Island in the Bahamas. The TM bands were transformed to minimize the depth-dependent variance in the bottom reflectance signal. Regression analyses were performed between the transformed bands and field measurements of seagrass standing crop (above-ground biomass). Regression equations using spectral data accounted for up to 80 per cent of the variability in seagrass biomass. The unexplained variance was ascribed to variations in bottom sediment color.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: International Journal of Remote Sensing (ISSN 0143-1161); 14; 3; p. 621-627.
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  • 123
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    Dynamic analysis of free-piston Stirling engine/linear alternator-load system - Experimentally validated (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: This paper discusses the effects of a variations in system parameters on the dynamic behavior of a Free-Piston Stirling Engine/Linear Alternator (FPSE/LA)-load system. The mathematical formulations incorporates both the mechanical and thermodynamic properties of the FPSE, as well as the electrical equations of the connected load. State-space technique in the frequency domain is applied to the resulting system of equations to facilitate the evaluation of parametric impacts on the system dynamic stability. Also included is a discussion on the system transient stability as affected by sudden changes in some key operating conditions. Some representative results are correlated with experimental data to verify the model and analytic formulation accuracies. Guidelines are given for ranges of the system parameters which will ensure an overall stable operation.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: In: IECEC '92; Proceedings of the 27th Intersociety Energy Conversion Engineering Conference, San Diego, CA, Aug. 3-7, 1992. Vol. 5 (A93-25851 09-44); p. 5.315-5.323.
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  • 124
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    Overview of the NASA Lewis component technology program for Stirling power converters (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: This paper presents an update on the NASA Lewis Stirling component technology program. The component technology program has been organized as part of the NASA Lewis effort to develop Stirling converter technology for space power applications. The Stirling space power program is part of the High Capacity Power element of the NASA Civil Space Technology Initiative. Lewis is also providing technical management of a DOE-funded project to develop Stirling converter systems for distributed dish solar terrestrial power applications. The Lewis component technology program is coordinated with the primary contract efforts of these projects but is aimed at longer term issues, advanced technologies, and independent assessments. Topics to be discussed include bearings, linear alternators, controls and load interaction, materials/life assessment, and heat exchangers.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: In: IECEC '92; Proceedings of the 27th Intersociety Energy Conversion Engineering Conference, San Diego, CA, Aug. 3-7, 1992. Vol. 5 (A93-25851 09-44); p. 5.283-5.288.
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  • 125
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    Advances in materials and current collecting networks for AMTEC electrodes (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: Electrode materials for the Alkali Metal Thermal to Electric Converter (AMTEC) play a significant role in the efficiency of the device. RhW and PtW alloys have been studied to determine the best performing material. While RhW electrodes typically have power densities somewhat lower than PtW electrodes, PtW performance is strongly influenced by the Pt/W ratio. The best performing Pt/W ratio is about 3.4. RhW electrodes sinter more slowly than PtW and are predicted to have operating lifetimes up to 40 years; PtW electrodes are predicted to have lifetimes up to 7 years. Interaction with the current collection network can significantly decrease lifetime by inducing metal migration and segregation and by accelerating the sintering rate.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: In: IECEC '92; Proceedings of the 27th Intersociety Energy Conversion Engineering Conference, San Diego, CA, Aug. 3-7, 1992. Vol. 3 (A93-25851 09-44); p. 3.7-3.12.
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    Coplanar waveguide feed for microstrip patch antennas (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A coplanar waveguide (CPW) loop is shown to be an effective low VSWR feed for microstrip antennas. The low VSWR transition between the CPW and the antenna is obtained without the use of a matching circuit, and it is relatively insensitive to the position of the antenna and the feed.
    Schlagwort(e): COMMUNICATIONS AND RADAR
    Materialart: Electronics Letters (ISSN 0013-5194); 28; 25; p. 2272-2274.
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  • 127
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    Remote spectral identification of surface aggregates by thermal imaging techniques - Progress report (1991)
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    Publikationsdatum: 2011-08-24
    Beschreibung: 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.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: 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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    Determination of water surface temperature based on the use of Thermal Infrared Multispectral Scanner data (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A straightforward method for compensating Thermal Infrared Multispectral Scanner (TIMS) digital data for the influence of atmospheric path radiance and the attenuation of target energy by the atmosphere is presented. A band ratioing model useful for estimating water surface temperatures, which requires no ground truth measurements, is included. A study conducted to test the potential of the model and the magnitudes of the corrections for atmosphere encountered is presented. Results of the study, which was based on data collected during an engineering evaluation flight of TIMS, indicate errors in the estimate of the surface temperature of the water fall from +/- 1.0 C for uncorrected data to +/- 0.4 C when data have been corrected according to the model presented. This value approaches the noise-limited thermal resolution of the sensor at the time of the flight.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: Geocarto International (ISSN 1010-6049); 7; 3; p. 3-8.
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  • 129
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    A systems approach to the commercialization of space communications technology - The NASA/JPL Mobile Satellite Program (1993)
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    Publikationsdatum: 2011-08-24
    Schlagwort(e): COMMUNICATIONS AND RADAR
    Materialart: Acta Astronautica (ISSN 0094-5765); 29; 9; p. 667-675.
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  • 130
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    Determination of microwave vegetation optical depth and single scattering albedo from large scale soil moisture and Nimbus/SMMR satellite observations (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The single scattering albedo and optical depth of typical savanna vegetation in Botswana (Africa) have been determined by inverse modelling using satellite observed microwave signatures and surface soil moisture. Soil emissivity was modelled using a multi-layer radiative transfer model. The study is based on large scale surface moisture data and Nimbus/SMMR 6-6 GHz and 37 GHz dual polarized brightness temperatures over a 3-year period. As compared to the optical depths, the derived single scattering albedos displayed only minor seasonal variations, whereas the values fit well within the range reported in the literature from laboratory and field experiments. Both 6-6 and 37GHz optical depths were found to be significantly related to NDVI-values derived from NOAA/AVHRR.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: International Journal of Remote Sensing (ISSN 0143-1161); 14; 10; p. 1875-1886.
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  • 131
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    Specularly modified vegetation indices to estimate photosynthetic activity (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The hypothesis tested was that some part of the ecosystem-dependent variability of vegetation indices was attributable to the effects of light specularly reflected by leaves. 'Minus specular' indices were defined excluding effects of specular light which contains no cellular pigment information. Results, both empirical and theoretical, show that the 'minus specular' indices, when compared to the traditional vegetation indices, potentially provide better estimates of the photosynthetic activity within a canopy - and therefore canopy primary production - specifically as a function of sun and view angles.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: International Journal of Remote Sensing (ISSN 0143-1161); 14; 9; p. 1815-1823.
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  • 132
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    Linear mixing model applied to coarse spatial resolution data from multispectral satellite sensors (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A linear mixing model was applied to coarse spatial resolution data from the NOAA Advanced Very High Resolution Radiometer. The reflective component of the 3.55-3.95 micron channel was used with the two reflective channels 0.58-0.68 micron and 0.725-1.1 micron to run a constrained least squares model to generate fraction images for an area in the west central region of Brazil. The fraction images were compared with an unsupervised classification derived from Landsat TM data acquired on the same day. The relationship between the fraction images and normalized difference vegetation index images show the potential of the unmixing techniques when using coarse spatial resolution data for global studies.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: International Journal of Remote Sensing (ISSN 0143-1161); 14; 11; p. 2231-2240.
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  • 133
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    On the use of passive microwaves at 37 GHz in remote sensing of vegetation (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Recently, a number of studies have investigated the use of the 37 GHz channels of the Nimbus-7 Scanning Multichannel Microwave Radiometer (SMMR) for vegetation monitoring and for studying synergisms between the SMMR and the NOAA Advanced Very High Resolution Radiometer (AVHRR). The approaches are promising but raise a number of issues concerning interpretation of the results, specifically on the relative effects of vegetation and other surface and atmospheric characteristics on the observed signal. This article analyzes the 37 GHz Microwave Polarization Difference Temperature (MPDT) in terms of its sensitivity to surface and atmospheric parameters. For this, a radiative transfer model is used which indicates some limitations of the MPDT index and suggests the importance of accounting for atmospheric effects in the data analysis. An alternative approach to the MPDT, including lower SMMR frequencies than 37 GHz, is discussed.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: International Journal of Remote Sensing (ISSN 0143-1161); 14; 10; p. 1931-1943.
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  • 134
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    Design of scanning spherical trireflector antennas with high aperture efficiency (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: It is frequently desirable to scan the main beam of a large antenna system without moving the main aperture structure. Spherical reflectors have excellent potential in this application. However, they are not commonly used because of poor aperture efficiency and high side lobes in traditional implementations. This paper introduces a new dual-subreflector feed system design which does not require oversizing the spherical main reflector to accommodate scan and yet permits a controlled aperture illumination. The design yields high aperture efficiency, low cross-polarization, and low side lobes.
    Schlagwort(e): COMMUNICATIONS AND RADAR
    Materialart: IEEE Transactions on Antennas and Propagation (ISSN 0018-926X); 41; 6; p. 778-786.
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  • 135
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    Using image pyramids for the visualization of large terrain data sets (1991)
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    Publikationsdatum: 2011-08-24
    Beschreibung: 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.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: International Journal of Imaging Systems and Technology (ISSN 0899-9457); p. 157-166.
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  • 136
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    An evaluation of short-wave-infrared (SWIR) data from the AVIRIS and GEOSCAN instruments for mineralogical mapping at Cuprite, Nevada (1991)
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    Publikationsdatum: 2011-08-24
    Beschreibung: 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.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: Geophysics (ISSN 0016-8033); 56; 9; p. 1432-1440.
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  • 137
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    Hydrologic applications of SAR derived soil moisture (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The MACHYDRO-90 was a multi-sensor aircraft campaign conducted to study drainage basin hydrology and the role of soil moisture in defining hydrologic characteristics and patterns. The results from the synthetic aperture radar (SAR) are presented. Data were collected over a period in which the soil conditions changed from dry to wet and then through a drying period which was close to ideal. Radar backscatter data are compared to detailed soil moisture samples taken to define soil moisture gradients within a watershed. The analysis also includes 40-MHz bandwidth SAR data, which provide very high spatial resolution. It is shown these data can be interpreted for hydrology and their application to hydrologic modeling is discussed.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1741-1743.
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    Mapping sub-tropical vegetation using multi-frequency, multi-polarization SAR data (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: In 1990 the NASA/JPL airborne synthetic aperture radar DC-8 (Airsar) was flown over an area in northern Belize and the surrounding countries of Guatemala and Mexico. The three-frequency polarimetric radar signatures of a variety of natural areas have been extracted, and many have a unique radar signature. Scattering mechanisms which may explain these signatures and results of an image classification technique are presented.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1686-1689.
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  • 139
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    Atmospheric effects on the NDVI - Strategies for its removal (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The compositing technique used to derive global vegetation index (NDVI) from the NOAA AVHRR radiances reduces the residual effect of water vapor and aerosol on the NDVI. The reduction in the atmospheric effect is shown using a comprehensive measured data set for desert conditions, and a simulation for grass with continental aerosol. A statistical analaysis of the probability of occurrence of aerosol optical thickness and precipitable water vapor measured in different climatic regimes is used for this simulation. It is concluded that for a long compositing period (e.g., 27 days), the residual aerosol optical thickness and precipitable water vapor are usually too small to be corrected. For a 9-day compositing, the residual average aerosol effect may be about twice the correction uncertainty. For Landsat TM or Earth Observing System Moderate Resolution Imaging Spectrometer (EOS-MODIS) data, the newly defined atmospherically resistant vegetation index (ARVI) is more promising than possible direct atmospheric correction schemes, except for heavy desert dust conditions.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1238-1241.
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    Modeling and measurement of microwave emission and backscattering from bare soil surfaces (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A multifrequency ground-based radiometer-scatterometer system working at frequencies between 3.0 GHz and 11.0 GHz has been used to study the effect of soil moisture and roughness on microwave emission and backscattering. The freezing and thawing effect of the soil surface and the changes of the surface roughness due to rain and erosion are reported. To analyze the combined active and passive data, a scattering model based on physical optics approximation for the low frequency and geometrical optics approximation for high frequency has been developed. The model is used to calculate the bistatic scattering coefficients from the surface. By considering the conservation of energy, the result has been integrated over a hemisphere above the surface to calculate the emissivity. The backscattering and emission model has been coupled with the observed data in order to extract soil moisture and surface roughness.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1190-1192.
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    An examination of the assumptions in the POLCAL cross-talk removal algorithm (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The POLCAL crosstalk removal algorithm is based on the statistical properties of the image background and does not need any corner reflector or active radar calibrator deployed in the scene. The advantage of being able to remove the crosstalk contamination without using external calibration targets gives rise to the consideration of algorithms based on clutter statistics in polarimetric synthetic aperture radar (SAR) images in more detail. The basic assumption of the POLCAL procedure is the decorrelation of copolarized and cross-polarized backscatter, which is valid for natural targets with azimuthal symmetry. This assumption and others regarding the properties of the imaged surface are examined. An improved version called POLCALII is presented, and its performance is compared with POLCAL.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1171-1173.
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    The effect of topography on radar scattering from vegetated areas (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: It is shown how radar scattering from vegetated areas is affected by the topography of the surface underneath the vegetation, and that by the use of a discrete scatterer model the dominant scattering mechanism may change drastically when the ground surface is tilted relative to the horizontal. In the case of a horizontal ground surface total scattering may be dominated by scattering off the tree trunks, followed by a reflection off the ground surface. It is shown that for a relatively small tilt in the ground surface the ground-trunk interaction term may be replaced by scattering from the branches alone as the dominant scattering mechanism. The effect of the topography is more pronounced for scattering by longer wavelengths. The implications for algorithms designed to infer forest woody biomass and soil and vegetation moisture using polarimetric synthetic aperture radar (SAR) data are discussed.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1132-1134.
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    KUREX-91 - A USSR/US study for global climate processes in steppe vegetation (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Researchers use satellite remote sensing of the earth's reflected and emitted radiation as correlated indices of the variables they measure on the ground or within the atmosphere. The Kursk 1991 Experiment (KUREX-91) was conducted to develop capabilities for monitoring global change, and to understand how the earth's land-surface vegetation and atmospheric boundary layer interact. The experiment enabled scientific interactions between the international participants, and comparisons of instruments and data. Intensive ground measurements were coordinated with helicopter, aircraft and satellite data acquisitions.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1035-1038.
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    Temporal decorrelation in repeat pass-radar interferometry (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Correlation in pass-to-pass, interferometric radar can be degraded by thermal noise, lack of parallelism between the radar flight tracks, spatial baseline noise, and surficial change. The effects of decorrelation due to thermal noise can be easily evaluated and removed, while those due slight angular changes between flight tracks are negligible for data acquired using near-repeat orbits. Empirical results obtained using images of Death Valley confirm that as the baseline increases, the overall correlation decreases due to spatial baseline noise. It is shown that areas of Cottonball Basin in Death Valley remained unchanged over the three-week period for which data was obtained, while a heavily forested area in Oregon exhibited significant temporal decorrelation. Lava in central Oregon also appeared to decorrelate. The results demonstrate that generation of height maps of heavily vegetated areas using pass-to-pass interferometry is practical, provided that the time between passes is at most several weeks.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 941-943.
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    Spectral vegetation indexes and the remote sensing of biophysical parameters (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Combinations of remotely sensed data from different spectral bands have been combined into spectral vegetation indexes (SVIs) and used to determine biophysical parameters. The characteristics of two-band SVIs made up of visible and near-infrared reflectances are examined. Two canopy reflectance models, a turbid media model and a geometrical model, are used to study the effects of different canopy structures on the measurement of leaf area index and the fraction of photosynthetically intercepted active radiation.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1017-1019.
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  • 146
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    Phase difference statistics related to sensor and forest parameters (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The information content of ordinary synthetic aperture radar (SAR) data is principally contained in the radiometric polarization channels, i.e., the four Ihh, Ivv, Ihv and Ivh backscattered intensities. In the case of clutter, polarimetric information is given by the four complex degrees of coherence, from which the mean polarization phase differences (PPD), correlation coefficients or degrees of polarization can be deduced. For radiometric features, the polarimetric parameters are corrupted by multiplicative speckle noise and by some sensor effects. The PPD distribution is related to the sensor, speckle and terrain properties. Experimental results are given for the variation of the terrain hh/vv mean phase difference and magnitude of the degree of coherence observed on bare soil and on different pine forest stands.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 779-781.
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    Cyclops - The JPL AIRSAR synoptic processor (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Capability for synoptic, or wide-area, SAR processing has been added to the JPL Aircraft Synthetic Aperture Radar System (AIRSAR) by means of the CYCLOPS synoptic processor. Polarimetric requirements have been relaxed so that a single node in the system can process SAR data with a throughput of three channels in 3.75 hours. Each channel consists of five minutes of full-range-swath data chosen from the twelve available AIRSAR polarization channels. Processed data consists of 16-look, 16-meter resolution imagery with a swath size of 60 km. The processor fully utilizes the available Doppler bandwidth and provides processing options for range migration correction, zero-Doppler deskew, frequency registration, and radiometric correction. The detected-power output product is scaled so as to provide sigma zero radiometric calibration.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 652-654.
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    Calibration of the AVHRR visible and near IR channels using radiances measured over remote ocean areas (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: An inflight absolute calibration method has been adapted and applied to channel 1 of the AVHRR. The approach is based on AVHRR observations in channels 1, 2 and 4. A rigorous cloud screening is performed, based on the homogeneity of the data in channel 1 and 2 and on the temperature in channel 4. In a combined approach, the off-nadir view satellite count in channel 2 is used to detect the aerosol optical thickness and loading and the count of channel 1 is used to calibrate this channel, based on the predictable Rayleigh scattering component. Water vapor data are used, and the channels are intercalibrated using the ratio between channels 1 and 2 over the glint region.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 9-11.
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    Attitude steering for space shuttle based synthetic aperture radars (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A technique is presented to steer the antenna beam to the zero-Doppler line for a spacecraft platform which operates in a non-zero roll attitude. The purposes of employing this attitude steering technique are reduction of the Doppler centroid error caused by the variation in target elevation; reduction of the Doppler centroid bound; and reduction of the Doppler drift. It is shown that a fixed attitude sequence can be easily accommodated in the radar command sequence to achieve nearly zero-Doppler steering. Implementation of this technique improves the image quality as well as simplifies the processor design.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 297-301.
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    Recent developments in space shuttle remote sensing, using hand-held film cameras (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The authors report on the advantages and disadvantages of a number of camera systems which are currently employed for space shuttle remote sensing operations. Systems discussed include the modified Hasselbad, the Rolleiflex 6008, the Linkof 5-inch format system, and the Nikon F3/F4 systems. Film/filter combinations (color positive films, color infrared films, color negative films and polarization filters) are presented.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 152-154.
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  • 151
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    Terrain effects on backscattering coefficients derived from multifrequency, polarimetric SAR data (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A set of multidate, multilook angle polarimetric SAR data, acquired in Pennsylvania during July 1990 was recorded to determine the effect of local incidence angle. Cosine-based and polynomial models are found to be equally good for correcting SAR data for local incidence angle effects. A modified approach, considering the correction factor as additive rather than multiplicative, gave better results. The standard error in the estimation of soil moisture improves from 8.1 to 5.8 after applying corrections to incidence angle effects.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 86-88.
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  • 152
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    MEDSAT - A remote sensing satellite for malaria early warning and control (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A remote sensing, medical satellite (MEDSAT) aids in the control of carrier (vector) borne disease. The prototype design is a light satellite to test for control of malaria. The design features a 340-kg satellite with visual/IR and SAR sensors in a low inclination orbit observing a number of worldwide test sites. The approach is to use four-band visual/IR and dual-polarized L-band SAR images obtained from MEDSAT in concert with in-situ data to estimate the temporal and spatial variations of malaria risk. This allows public health resources to focus on the most vulnerable areas at the appropriate time. It is concluded that a light-satellite design for a MEDSAT satellite with a Pegasus launch is feasible.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 28-30.
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  • 153
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    A system for verifying models and classification maps by extraction of information from a variety of data sources (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Recent updates to a geographical information system (GIS) called VICAR (Video Image Communication and Retrieval)/IBIS are described. The system is designed to handle data from many different formats (vector, raster, tabular) and many different sources (models, radar images, ground truth surveys, optical images). All the data are referenced to a single georeference plane, and average or typical values for parameters defined within a polygonal region are stored in a tabular file, called an info file. The info file format allows tracking of data in time, maintenance of links between component data sets and the georeference image, conversion of pixel values to `actual' values (e.g., radar cross-section, luminance, temperature), graph plotting, data manipulation, generation of training vectors for classification algorithms, and comparison between actual measurements and model predictions (with ground truth data as input).
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 245-247.
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  • 154
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    Analysis of scattering behavior and radar penetration in AIRSAR data (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A technique is presented to physically characterize changes in radar backscatter with frequency in multifrequency single polarization radar images that can be used as a first step in the analysis of the data and the retrieval of geophysical parameters. The technique is automatic, relatively independent of the incidence angle, and only requires a good calibration accuracy between the different frequencies. The technique reveals large areas where scattering changes significantly with frequency and whether the surface has the characteristics of a smooth, slightly rough, rough, or very rough surface.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 134-136.
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  • 155
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    Monsoon '90 - Preliminary SAR results (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Multifrequency polarimetric synthetic aperture radar (SAR) images of the Walnut Gulch watershed near Tombstone, Arizona were acquired on 28 Mar. 1990 and on 1 Aug. 1990. Trihedral corner reflectors were deployed prior to both overflights to allow calibration of the two SAR data sets. During both overflights, gravimetric soil moisture and dielectric constant measurements were made. Detailed vegetation height, density, and water content measurements were made as part of the Monsoon 1990 Experiment. Preliminary results based on analysis of the multitemporal polarimetric SAR data are presented. Only the C-band data (5.7-cm wavelength) radar images show significant difference between Mar. and Aug., with the strongest difference observed in the HV images. Based on the radar data analysis and the in situ measurements, we conclude that these differences are mainly due to changes in the vegetation and not due to the soil moisture changes.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 71-73.
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  • 156
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    Mapping new and old worlds with laser altimetry (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Spaceborne laser altimeter systems intended to operate at lunar and Martian orbits are reviewed. Laser altimeter systems capable of long lifetimes with centimeter precision ranging electronics are considered to be essential components of NASA's EOS.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: Photonics Spectra (ISSN 0731-1230); 27; 4; p. 89-94.
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  • 157
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    Opportunities in the commercial uses of remote sensing and GIS technologies - An overview of NASA's Visiting Investigator Program at Stennis Space Center (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The Visiting Investigator Program (VIP) developed at NASA-Stennis' Science and Technology Laboratory (STL) allows U.S. industry to use the specialized resources of STL in the fields of remote sensing and GIS, with a view to the development of new commercial processes and improved services. Attention is given to the novel agreement mechanisms developed by NASA to implement VIP. These agreements encompass a memorandum of understanding, a technical exchange agreement, a sponsored-transfer agreement, a proprietary work agreement, and a joint endeavor agreement.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: PE&RS - Photogrammetric Engineering and Remote Sensing (ISSN 0099-1112); 59; 6; p. 935-939.
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  • 158
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    Maximum-likelihood block detection of noncoherent continuous phase modulation (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: This paper examines maximum-likelihood block detection of uncoded full response CPM over an additive white Gaussian noise (AWGN) channel. Both the maximum-likelihood metrics and the bit error probability performances of the associated detection algorithms are considered. The special and popular case of minimum-shift-keying (MSK) corresponding to h = 0.5 and constant amplitude frequency pulse is treated separately. The many new receiver structures that result from this investigation can be compared to the traditional ones that have been used in the past both from the standpoint of simplicity of implementation and optimality of performance.
    Schlagwort(e): COMMUNICATIONS AND RADAR
    Materialart: IEEE Transactions on Communications (ISSN 0090-6778); 41; 1; p. 90-98.
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  • 159
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    Lava flow topographic measurements for radar data interpretation (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Topographic profiles at 25- and 5-cm horizontal resolution for three sites along a lava flow on Kilauea Volcano are presented, and these data are used to illustrate techniques for surface roughness analysis. Height and slope distributions and the height autocorrelation function are evaluated as a function of varying lowpass filter wavelength for the 25-cm data. Rms slopes are found to increase rapidly with decreasing topographic scale and are typically much higher than those found by modeling of Magellan altimeter data for Venus. A more robust description of the surface roughness appears to be the ratio of rms height to surface height correlation length. For all three sites this parameter falls within the range of values typically found from model fits to Magellan altimeter waveforms. The 5-cm profile data are used to estimate the effect of small-scale roughness on quasi-specular scattering.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: Geophysical Research Letters (ISSN 0094-8276); 20; 9; p. 831-834.
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  • 160
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    Improved Li-TiS2 cell cycling in ether-based electrolytes with synergistic additives (1991)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Results of the application of 2-MeF and KOH additives to improve the lithium stability in THF, dioxolane, and THF/2-MeTHF solvent-based electrolytes are presented. The stability of these electrolytes with and without additives is evaluated by microcalorimetry and AC impedance spectroscopy. A novel method, cathode turnover number, is proposed to represent the electrolyte performance in a given system. The lithium cycling efficiency and cathode turnover number of the electrolytes are calculated from the cycle life data in experimental Li-TiS2 cells. Overall, THF/2-MeTHF electrolyte containing 2-MeF and/or KOH exhibited higher stability, lithium cycling efficiency, and cathode turnover number compared to THF and dioxolane electrolytes with and without additives.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: In: Primary and secondary lithium batteries (A93-37355 14-25); p. 280-292.
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  • 161
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    Evaluation of lithium alloy anode materials for Li-TiS2 cells (1991)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A study was performed to select candidate lithium alloy anode materials and establish selection criteria. Some of the selected alloy materials were evaluated for their electrochemical properties and performance. This paper describes the criteria for the selection of alloys and the findings of the studies. Li-Si and Li-Cd alloys have been found to be unstable in the EC+2-MeTHF-based electrolyte. The Li-Al alloy system was found to be promising among the alloy systems studied in view of its stability and reversibility. Unfortunately, the large volume changes of LiAl alloys during charge/discharge cycling cause considerable 'exfoliation' of its active mass. This paper also describes ways how to address this problem. The rate of disintegration of this anode would probably be surpressed by the presence of an inert solid solution or a uniform distribution of precipitates within the grains of the active mass. It was discovered that the addition of a small quantity of Mn may improve the mechanical properties of LiAl. In an attempt to reduce the Li-Al alloy vs. Li voltage, it was observed that LiAlPb(0.1)Cd(0.3) material can be cycled at 1.5 mA/sq cm without exfoliation of the active mass.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: In: Primary and secondary lithium batteries (A93-37355 14-25); p. 395-406.
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  • 162
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    Directivity versus element spacing for a scanning array (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The results of the present examination of the relationship of directivity with element spacings of linear, rectangular, and hexagonal arrays indicate that element spacings for optimal directivity vary with scan angles; this is especially true in the case of changes in aperture sizes and the appearance of grating lobes in the visible space. Grating lobe effects are more pronounced for isotropic than for directive element arrays. Directivity decreases as the beam scans off from boresight, and rapidly diminishes for scans over 30 deg. The hexagonal array has higher directivity for scans of less than 20 deg, and the linear array for those over 30 deg.
    Schlagwort(e): COMMUNICATIONS AND RADAR
    Materialart: Microwave and Optical Technology Letters (ISSN 0895-2477); 6; 6; p. 361-363.
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  • 163
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    Multiresolution image gathering and restoration (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: In this paper we integrate multiresolution decomposition with image gathering and restoration. This integration leads to a Wiener-matrix filter that accounts for the aliasing, blurring, and noise in image gathering, together with the digital filtering and decimation in signal decomposition. Moreover, as implemented here, the Wiener-matrix filter completely suppresses the blurring and raster effects of the image-display device. We demonstrate that this filter can significantly improve the fidelity and visual quality produced by conventional image reconstruction. The extent of this improvement, in turn, depends on the design of the image-gathering device.
    Schlagwort(e): COMMUNICATIONS AND RADAR
    Materialart: Journal of Visual Communication and Image Representation (ISSN 1047-3203); 3; 4; p. 356-363.
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  • 164
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    An algorithm for the estimation of water temperatures from thermal multispectral airborne remotely sensed data (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A method for water temperature estimation on the basis of thermal data is presented and tested against NASA's Thermal IR Multispectral Scanner. Using realistic bounds on emissivities, temperature bounds are calculated and refined to estimate a tighter bound on the emissivity of the source. The method is useful only when a realistic set of bounds can be obtained for the emissivities of the data.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: Automatic object recognition II; Proceedings of the Meeting, Orlando, FL, Apr. 22-24, 1992 (A93-33243 12-63); p. 406-416.
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  • 165
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    Update on the advanced Stirling conversion system project for 25 kW dish Stirling applications (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Technology development for Stirling convertors directed toward a dynamic power source for space applications is examined. The free-piston Stirling engine has the potential for both solar and nuclear space power applications. Two parallel design directions feature a solar receiver/liquid metal heat transport system, and a free-piston Stirling convertor which incorporates a linear alternator to directly provide the electrical output of about 25 kW to a utility grid. The Cummins Engine Company (CEC) free-piston Stirling convertor incorporates a linear alternator along with hydrodynamic gas bearings to provide noncontacting, wear-free support to the pistons. The Stirling Technology Company design incorporates linear alternator technology with flexures that provide noncontacting support while also supplying much of the spring stiffness needed to obtain proper resonance.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: In: IECEC '92; Proceedings of the 27th Intersociety Energy Conversion Engineering Conference, San Diego, CA, Aug. 3-7, 1992. Vol. 5 (A93-25851 09-44); p. 5.229-5.235.
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  • 166
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    PEM fuel cell stack heat and mass management (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: PEM stacks are under evaluation as candidates for future space power technology. Results of long-term operation on a set of contemporary stacks fitted with different proton exchange membrane materials are given. Data on water balances show effects of membrane materials on stack performance.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: In: IECEC '92; Proceedings of the 27th Intersociety Energy Conversion Engineering Conference, San Diego, CA, Aug. 3-7, 1992. Vol. 3 (A93-25851 09-44); p. 3.407-3.411.
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  • 167
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    Prediction of performance of two-phase flow nozzle and liquid metal magnetohydrodynamic (LMMHD) generator for no slip condition (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Two-phase LMMHD energy conversion systems have potentially significant advantages over conventional systems such as higher thermal efficiency and substantial simplicity with lower capital and maintenance costs. Maintenance of low velocity slip is of importance for achieving high generator efficiency. A bubbly flow pattern ensures very low velocity slip. The full governing equations have been written out, and a computer prediction code has been developed to analyze performance of a two-phase flow LMMHD generator and nozzle under conditions of no slip. Three different shapes of a LMMHD generator have been investigated. Electrical power outputs are in the 20 kW range. Generator efficiency exceeds 71 percent at an average void fraction of about 70 percent. This is an appreciable performance for a short generator without insulating vanes for minimizing electrical losses in the end regions.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: In: IECEC '92; Proceedings of the 27th Intersociety Energy Conversion Engineering Conference, San Diego, CA, Aug. 3-7, 1992. Vol. 3 (A93-25851 09-44); p. 3.391-3.399.
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  • 168
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    Assessment of the US industrial program for AMTEC development (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The Alkali Metal Thermal to Electric Converter (AMTEC) is a static energy conversion technology that is expected to provide low mass thermal to electric conversion with efficiencies between 20 and 35 percent. The U.S. program to develop this technology for space power applications has grown substantially over the past 3 years. This expanding program has brought together several laboratories and technical consultants, in separately sponsored projects, to develop the key elements of the technology. An assessment of this multiparty program indicates that, in general, the effort has focused on the high priority technical elements with only moderate overlap between individual projects. There are, however, several areas where additional coordination is needed between major participants in the existing projects, and other areas where new projects should be started, in order to provide reliable space power systems without unnecessary delays.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: In: IECEC '92; Proceedings of the 27th Intersociety Energy Conversion Engineering Conference, San Diego, CA, Aug. 3-7, 1992. Vol. 3 (A93-25851 09-44); p. 3.215-3.220.
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  • 169
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    Nickel Hydrogen Battery Expert System (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The Nickel Cadmium Battery Expert System-2, or 'NICBES-2', which was used by the NASA HST six-battery testbed, was subsequently converted into the Nickel Hydrogen Battery Expert System, or 'NICHES'. Accounts are presently given of this conversion process and future uses being contemplated for NICHES. NICHES will calculate orbital summary data at the end of each orbit, and store these files for trend analyses and rules-generation.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: In: IECEC '92; Proceedings of the 27th Intersociety Energy Conversion Engineering Conference, San Diego, CA, Aug. 3-7, 1992. Vol. 1 (A93-25851 09-44); p. 1.197-1.201.
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    On the effects of phase jitter on QPSK lock detection (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The performance of a QPSK (quadrature phase-shift keying) lock detector is described, taking into account the degradation due to carrier phase jitter. Such an analysis is necessary for accurate performance prediction purposes in scenarios where both the loop SNR is low and the estimation period is short. The derived formulas are applicable to several QPSK loops and are verified using computer simulations.
    Schlagwort(e): COMMUNICATIONS AND RADAR
    Materialart: IEEE Transactions on Communications (ISSN 0090-6778); 41; 7; p. 1043-1046.
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  • 171
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    Analysis of rocket beacon transmissions for computerized reconstruction of ionospheric densities (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Three methods are described to obtain ionospheric electron densities from transionospheric, rocket-beacon TEC data. First, when the line-of-sight from a ground receiver to the rocket beacon is tangent to the flight trajectory, the electron concentration can be obtained by differentiating the TEC with respect to the distance to the rocket. A similar method may be used to obtain the electron-density profile if the layer is horizontally stratified. Second, TEC data obtained during chemical release experiments may be interpreted with the aid of physical models of the disturbed ionosphere to yield spatial maps of the modified regions. Third, computerized tomography (CT) can be used to analyze TEC data obtained along a chain of ground-based receivers aligned along the plane of the rocket trajectory. CT analysis of TEC data is used to reconstruct a 2D image of a simulated equatorial plume. TEC data is computed for a linear chain of nine receivers with adjacent spacings of either 100 or 200 km. The simulation data are analyzed to provide an F region reconstruction on a grid with 15 x 15 km pixels. Ionospheric rocket tomography may also be applied to rocket-assisted measurements of amplitude and phase scintillations and airglow intensities.
    Schlagwort(e): COMMUNICATIONS AND RADAR
    Materialart: Radio Science (ISSN 0048-6604); 28; 4; p. 613-627.
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  • 172
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    Fractal dimension analyses of lava surfaces and flow boundaries (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: An improved method of estimating fractal surface dimensions has been developed. The accuracy of this method is illustrated using artificially generated fractal surfaces. A slightly different from usual concept of linear dimension is developed, allowing a direct link between that and the corresponding surface dimension estimate. These methods are applied to a series of images of lava flows, representing a variety of physical and chemical conditions. These include lavas from California, Idaho, and Hawaii, as well as some extraterrestrial flows. The fractal surface dimension estimations are presented, as well as the fractal line dimensions where appropriate.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: Visual information processing II; Proceedings of the Meeting, Orlando, FL, Apr. 14-16, 1993 (A93-53022 23-63); p. 220-229.
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    AVHRR-LAC estimates of forest area in Madagascar, 1990 (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Three AVHRR-LAC data sets acquired in September 1990 and January 1991 were used to map the forest resources of Madagascar. The island was partitioned into four strata to include: (1) the western hardwoods, (2) the central grasslands, (3) the eastern rainforest, and (4) spiny forest. Each stratum was classified separately using AVHRR-LAC data in conjunction with 1984-1988 Landsat-MSS photoproducts. The results of AVHRR classification indicate that approximately 11 percent of the island is covered by forest. Estimates of forest area, by stratum, are as follows: western hardwoods, 6697 sq km; central grasslands, 2830 sq km; eastern rainforest 34,167 sq km; and spiny forest, 17,224 sq km. The total forest area on the 587,041 sq km island is estimated to be 60,918 sq km. The AVHRR forest map was compared to a mid-1970s land cover map which was developed using Landsat-MSS photoproducts. The average class agreement between the mid 1970s ground reference map and the 1990 AVHRR-LAC map was 78.2 percent, the overall accuracy was 81.1 percent. Much of the per-pixel disagreement between the ground reference and AVHRR maps involved areas identified as forest in the 1970s and as nonforest in 1990.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: International Journal of Remote Sensing (ISSN 0143-1161); 14; 8; p. 1463-1475.
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    A new clustering algorithm applicable to multispectral and polarimetric SAR images (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: We describe an application of a scale-space clustering algorithm to the classification of a multispectral and polarimetric SAR image of an agricultural site. After the initial polarimetric and radiometric calibration and noise cancellation, we extracted a 12-dimensional feature vector for each pixel from the scattering matrix. The clustering algorithm was able to partition a set of unlabeled feature vectors from 13 selected sites, each site corresponding to a distinct crop, into 13 clusters without any supervision. The cluster parameters were then used to classify the whole image. The classification map is much less noisy and more accurate than those obtained by hierarchical rules. Starting with every point as a cluster, the algorithm works by melting the system to produce a tree of clusters in the scale space. It can cluster data in any multidimensional space and is insensitive to variability in cluster densities, sizes and ellipsoidal shapes. This algorithm, more powerful than existing ones, may be useful for remote sensing for land use.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: IEEE Transactions on Geoscience and Remote Sensing (ISSN 0196-2892); 31; 3; p. 634-644.
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    Scientific issues and potential remote-sensing requirements for plant biochemical content (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Application of developments in imaging spectrometry to the study of terrestrial ecosystems, which began in 1983, demonstrate the potential to estimate lignin and nitrogen concentrations of plant canopies by remote-sensing techniques. Estimation of these parameters from the first principles of radiative transfer and the interactions of light with plant materials is not presently possible, principally because of lack of knowledge about internal leaf scattering and specific absorption involving biochemical compounds. From the perspective of remote-sensing instrumentation, sensors are needed to support derivative imaging spectroscopy. Biochemical absorption features tend to occur in functional groupings throughout the 1100- to 2500-nm region. Derivative spectroscopy improves the information associated with the weaker, narrower absorption features of biochemical absorption that are superimposed on the strong absolute variations due to foliar biomass, pigments, and leaf water content of plant canopies. Preliminary sensor specifications call for 8-nm bandwidths at 2-nm centers in four spectral regions (about 400 bands total) and a signal-to-noise performance of at least 1000:1 for 20 percent albedo targets in the 2000-nm region.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: Journal of Imaging Science and Technology (ISSN 8750-9237); 36; 5; p. 446-456.
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  • 176
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    Diffraction analysis of frequency selective reflector antennas (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: In this paper, a unified computational technique is presented which allows the incorporation of the curved frequency-selective surface (FSS) geometry in the computation of the reflector antenna radiation pattern. The scattered fields from an illuminated FSS reflector are formalized using Huygens' principle in such a way that the 'reflecting' and the 'transparent' FSS subreflector cases are treated identically and the thickness of the FSS subreflector remains arbitrary. The analysis utilizes local surface coordinates to describe the reflection/transmission matrices of the FSS subreflector where it is assumed that these matrices are available. In most cases one may use the local tangent plane for approximating the plane of the FSS in the local coordinate surface of the reflector. The paper demonstrates how the local curved coordinate system can be introduced in the diffraction modeling of FSS reflectors and its importance in accurately predicting the side-lobe and crosspolarization levels. Results of numerical simulations are presented for several FSS subreflector configurations.
    Schlagwort(e): COMMUNICATIONS AND RADAR
    Materialart: IEEE Transactions on Antennas and Propagation (ISSN 0018-926X); 41; 4; p. 476-487.
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  • 177
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    Age discrimination among eruptives of Menengai Caldera, Kenya, using vegetation parameters from satellite imagery (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Results are presented of an investigation to determine the degree to which digitally processed Landsat TM imagery can be used to discriminate among vegetated lava flows of different ages in the Menengai Caldera, Kenya. A selective series of five images, consisting of a color-coded Landsat 5 classification and four color composites, are compared with geologic maps. The most recent of more than 70 postcaldera flows within the caldera are trachytes, which are variably covered by shrubs and subsidiary grasses. Soil development evolves as a function of time, and as such supports a changing plant community. Progressively older flows exhibit the increasing dominance of grasses over bushes. The Landsat images correlated well with geologic maps, but the two mapped age classes could be further subdivided on the basis of different vegetation communities. It is concluded that field maps can be modified, and in some cases corrected by use of such imagery, and that digitally enhanced Landsat imagery can be a useful aid to field mapping in similar terrains.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: Geocarto International (ISSN 1010-6049); 8; 1; p. 51-59.
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  • 178
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    Design concepts of high power bipolar rechargeable lithium battery (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The present study shows that current bipolar Li/TiS2 batteries using a 0.38 mm thick TiS2 bipolar plate can yield moderate specific power and also high specific energy battery. The computer design studies project that a 100 V, 10 A h bipolar Li/TiS2 battery can achieve 150 W h/kg, 210 W h/l, and 150 W/kg. The unoptimized experimental bipolar Li/TiS2 batteries (3 cells, 90 mA h) exhibited 47 W h/kg, 90 W h/l, and 140 W/kg. Preliminary results on the cycleability of the bipolar batteries are demonstrated. The results also show that enhanced rate capability can be achieved by using pulse discharge and longer rest period between pulses.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: Journal of Power Sources (ISSN 0378-7753); 43; 1-3; p. 327-338.
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  • 179
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    A high power lithium thionyl chloride battery for space applications (1993)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A high power, 28 V, 330 A h, active lithium thionyl chloride battery has been developed for use as main and payload power sources on an expendable launch vehicle. Nine prismatic cells, along with the required electrical components and a built-in heater system, are efficiently packaged resulting in significant weight savings over presently used silver-zinc batteries. The high rate capability is achieved by designing the cells with a large electrochemical surface area and impregnating an electrocatalyst, polymeric phthalocyanine, into the carbon cathodes. Passivation effects are reduced with the addition of sulfur dioxide into the thionyl chloride electrolyte solution. The results of conducting a detailed thermal analysis are utilized to establish the heater design parameters and the thermal insulation requirements of the battery. An analysis of cell internal pressure and vent characteristics clearly illustrates the margins of safety under different operating conditions. Performance of fresh cells is discussed using polarization scan and discharge data at different rates and temperatures. Self-discharge rate is estimated based upon test results on cells after storage. Results of testing a complete prototype battery are described.
    Schlagwort(e): ENERGY PRODUCTION AND CONVERSION
    Materialart: Journal of Power Sources (ISSN 0378-7753); 43; 1-3; p. 317-326.
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  • 180
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    Estimation of bare soil evaporation using multifrequency airborne SAR (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: It is shown that for homogeneous areas soil moisture can be derived from synthetic aperture radar (SAR) measurements, so that the use of microwave remote sensing can given realistic estimates of energy fluxes if coupled to a simple two-layer model repesenting the soil. The model simulates volumetric water content (Wg) using classical meterological data, provided that some of the soil thermal and hydraulic properties are known. Only four parameters are necessary: mean water content, thermal conductivity and diffusitivity, and soil resistance to evaporation. They may be derived if a minimal number of measured values of Wg and surface layer temperature (Tg) are available together with independent measurements of energy flux to compare with the estimated values. The estimated evaporation is shown to be realistic and in good agreement with drying stage theory in which the transfer of water in the soil is in vapor form.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1747-1749.
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  • 181
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    Morphological, anatomical, and chemical characteristics of needle and branch samples of Siberian fir (Abies Siberica) (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: In August, 1991, needle and branch samples of Siberian fir were collected from undisturbed forest stands along an elevation gradient ranging from 2300 ft to 4450 ft. Four study sites were selected on west-facing slopes, and a standard set of measurements and collections was made. First-, second-, and third-year needles were collected for anatomical assessment. A visual assessment of the forest stand conditions at each site included an evaluation of canopy morphology needle, coloration, increment growth, and the state of health of a specific type of lichen. The heaviest damage to forest stands (extensive foliar loss, needle discoloration, dieback of terminal growth) occurs at an intermediate elevation site (3400 ft/1037 m). The least amount of damage was recorded at the lowest elevation site (2300 ft/701 m). Only slight damage occurs at the highest elevation site (4450 ft/1357 m). Some degree of flagging occurs at all sites. Several lines of evidence suggest that the damage occurring in this area is recent in origin (incipient).
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1289-1291.
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  • 182
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    Calibration and Change Detection of [Alaska Satellite Facility] ASF/ERS-1 SAR Image Data (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The results of a calibration analysis performed on ERS-1 synthetic aperture radar (SAR) images produced by the Alaska SAR facility (ASF) are presented, together with some preliminary results on change detection on the Alaskan north slope derived from the same images. Image quality, geometric and radiometric fidelity, and repeat pass radiometric stability have all been determined to be satisfactory. A calibration workstation has been designed and implemented for use in operational data quality analysis of ASF data products. Higher-level data analysis programs have been developed for interferometry, texture analysis, and change detection.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX.; Vol. 2; p. 1164-1166.; A93-47551 20-43)
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  • 183
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    Inversion of snow parameters by neural network with iterative inversion (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The inversion of snow parameters from passive microwave remote sensing measurements is performed with a neural network trained with a dense media multiple scattering model. A constrained iterative inversion scheme is used. Inversion of four parameters is performed from five brightness temperatures. The four parameters are: mean grain size of ice particles in snow, snow density, snow temperature, and snow depth. The five brightness temperatures are that of 19-GHz vertical polarization, 19-GHz horizontal polarization, 22-GHz vertical polarization, 37-GHz vertical polarization, and 37-GHz horizontal polarization. Based on the neural network constrained iterative inversion algorithm, synthetic mapping of the terrain is performed. The retrieval of synthetic mapping has been achieved. The incorporation of ground truth information is considered.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1061-1063.
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  • 184
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    Spectral bidirectional and hemispherical reflectance characteristics of selected sites in the Streletskaya steppe (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Measurements of plant canopy bidirectional reflectance made by the PARABOLA (portable apparatus for rapid acquisition of bidirectional observations of the land and atmosphere) instrument in three spectral bands are analyzed for steppe grassland sites of differing productivity levels. The variation of spectral reflectance and the normalized difference vegetation index in the solar principal plane is presented. Comparisons are made with PARABOLA measurements from selected first ISLSCP field experiment (FIFE) grassland sites in the Konza prairie, Kansas. The Streletskaya steppe sites showed no strong hot spot reflectance, while this effect was present in some FIFE sites but absent in others. The hot spot effect seems to be dependent on canopy geometry and background reflectance characteristics of these sites. Spectral hemispherical reflectance was computed from the angular integration of the bidirectional measurements for the steppe sites. Total shortwave albedo was estimated from these hemispherical reflectance measurements and compared to albedo measured by pyranometers. The albedo estimates from PARABOLA were found to be approximately 12-17 percent higher than the pyranometer measurements.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1053-1055.
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  • 185
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    Polarization signatures for abandoned agricultural fields in the Manix Basin area of the Mojave Desert - Can polarimetric SAR detect desertification? (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: Radar backscatter from abandoned circular alfalfa fields in the Manix Basin area of the Mojave desert shows systematic changes with length of abandonment. The obliteration of circular planting rows by surface processes could account for the disappearance of bright spokes, which seem to be reflection patterns from remnants of the planting rows, with increasing length of abandonment. An observed shift in the location of the maximum L-band copolarization return away from VV, as well as an increase in surface roughness, both occurring with increasing age of abandonment, seems to be attributable to the formation of wind ripples on the relatively vegetationless fields.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 947-949.
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  • 186
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    JPL AIRSAR processing activities and developments (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Significant progress has been made in processing the Jet Propulsion Laboratory airborne synthetic aperture radar (JPL AIRSAR) data. These advances include increased swath width, increased number of looks; increased processor throughput, and decreased processor turnaround time (including photo product). These advances are made possible by new processing algorithms, software, and hardware. In addition to these processor improvements, a more mature understanding of the AIRSAR system in general has made it possible for the processor to routinely produce calibrated data based on internal calibration tests. Starting with the processing of 1991 acquired data, this new processor has become operational for the routine processing of AIRSAR data.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1152-1154.
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  • 187
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    Modeling of SAR returns from a red pine stand (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Bright P-band radar returns from red pine forests have been observed on synthetic aperture radar (SAR) images in Bangor, Maine. A plot of red pine trees was selected for the characterization and modeling to understand the cause of the high P-band returns. The red pine stand under study consisted of mature trees. Diameter at breast height (DBH) measurements were made to determine stand density as a function of tree diameter. Soil moisture and bulk density measurements were taken along with ground rough surface profiles. Detailed biomass measurements of the needles, shoots, branches, and trunks were also taken. These site statistics have been used in a distorted Born approximation model of the forest. Computations indicate that the direct-reflected or the double-bounce contributions from the ground are responsible for the high observed P-band returns for HH polarization.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1138-1140.
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  • 188
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    Radar measurement of forested areas during OTTER (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: To test a forest ecosystem model in the OTTER (Oregon ecosystem research) project, it is desirable to find forest canopy parameters via radar remote sensing measurements. Conventionally, forest biomass, along with quantities such as the leaf area index, drive the model. It is shown that the radar backscatter is not uniquely related to biomass. A sensitivity study is carried out using a forward scattering model to determine the variation of radar cross section as a function of several forest parameters. The results are used to find suitable quantities to recover via radar experiments. A parameter estimation scheme is developed to calculate some preliminary statistical properties of the forest.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1135-1137.
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  • 189
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    Classification of remotely sensed data using OCR-inspired neural network techniques (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Neural networks have been applied to classifications of remotely sensed data with some success. To improve the performance of this approach, an examination was made of how neural networks are applied to the optical character recognition (OCR) of handwritten digits and letters. A three-layer, feedforward network, along with techniques adopted from OCR, was used to classify Landsat-4 Thematic Mapper data. Good results were obtained. To overcome the difficulties that are characteristic of remote sensing applications and to attain significant improvements in classification accuracy, a special network architecture may be required.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1081-1083.
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  • 190
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    Inversion of parameters for semiarid regions by a neural network (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Microwave brightness temperatures obtained from a passive radiative transfer model are inverted through use of a neural network. The model is applicable to semiarid regions and produces dual-polarized brightness temperatures for 6.6-, 10.7-, and 37-GHz frequencies. A range of temperatures is generated by varying three geophysical parameters over acceptable ranges: soil moisture, vegetation moisture, and soil temperature. A multilayered perceptron (MLP) neural network is trained with a subset of the generated temperatures, and the remaining temperatures are inverted using a backpropagation method. Several synthetic terrains are devised and inverted by the network under local constraints. All the inversions show good agreement with the original geophysical parameters, falling within 5 percent of the actual value of the parameter range.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 2 (A93-47551 20-43); p. 1075-1077.
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    Moderate resolution imaging spectroradiometer (MODIS) and observations of the land surface (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The moderate resolution imaging spectroradiometer (MODIS) is a NASA facility instrument that is being designed for flight on the Earth Observing System (EOS) series of missions. It is designed to measure biophysical states and dynamics of the land, atmosphere, and ocean. Plans are required for use of other instruments that will be accompanying MODIS on the EOS missions, such as the High-Resolution Imaging Spectrometer (HIRIS) and the Multi-angle Imaging Spectro-Radiometer (MISR). The HIRIS instrument, a spectrometer operating in the visible to shortwave infrared parts of the spectrum, would be employed in combination with the MODIS to understand the impact of sampling the spectrum and the effects of land cover mixtures within the MODIS pixel. The MISR will help in understanding the effects of anisotropy in reflected solar radiation. Both instruments will work in combination with MODIS to better quantify the effects of the atmosphere on observations of surface properties.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 549-551.
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  • 192
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    The role of specular reflectance in surface anisotropy (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: For smooth surfaces, specular reflection constitutes a major source of anisotropy in the surface bidirectional reflectance and introduces a strong illumination angle dependence in diurnal albedo. A prior formulation has been employed by the authors to account for the surface anisotropy of other natural surfaces. It is shown that this formulation is appropriate to successfully explain the specular characteristics of other rough surfaces as well as that of the ocean. The angular dependence of the diffuse component of the reflected radiance is explained using the Ahmad-Deering formulation, which is based on Chandrasekhar's radiative transfer solution. Results for a smooth silt-playa lake bed in a volcanic region of Nevada are presented. It is shown that this formulation is capable of explaining the specular features measured in the field and can be effectively used in any surface bidirectional reflectance model.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 514-516.
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  • 193
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    Goniometric measurements of light scattered in the principal plane from leaves (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A laboratory goniometer was designed and built by NASA for acquiring bidirectional scattering data in the principal plane from leaves. Goniometric measurements were taken on individual tree leaves of yellow poplar, red maple, and red oak. Reflectance measurements were taken every 5* and transmittance measurements every 10 in the principal plane. The results indicate that light reflected from leaves usually has a significant specular component. Reflectances measured for 60 incident angle were the most specular. The most isotropic scattering occurred with transmitted light and with 0 incident light reflected from the abaxial surface. The most significant difference observed between the species was due to the heavy wax layer found on the abaxial surface of red oak, which caused the abaxial reflectance to be more specular than it was in the other two species.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 508-510.
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    Synergistic use of active and passive microwave in soil moisture estimation (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Data gathered during the MACHYDRO experiment in central Pennsylvania in July 1990 have been utilized to study the synergistic use of active and passive microwave systems for estimating soil moisture. These data sets were obtained during an eleven-day period with NASA's Airborne Synthetic Aperture Radar (AIRSAR) and Push-Broom Microwave Radiometer (PBMR) over an instrumented watershed which included agricultural fields with a number of different crop covers. Simultaneous ground truth measurements were also made in order to characterize the state of vegetation and soil moisture under a variety of meteorological conditions. A combination algorithm is presented as applied to a representative corn field in the MACHYDRO watershed.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 492-494.
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    Soil moisture needs in earth sciences (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The author reviews the development of passive and active microwave techniques for measuring soil moisture with respect to how the data may be used. New science programs such as the EOS, the GEWEX Continental-Scale International Project (GCIP) and STORM, a mesoscale meteorology and hydrology project, will have to account for soil moisture either as a storage in water balance computations or as a state variable in-process modeling. The author discusses future soil moisture needs such as frequency of measurement, accuracy, depth, and spatial resolution, as well as the concomitant model development that must proceed concurrently if the development in microwave technology is to have a major impact in these areas.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 477-479.
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  • 196
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    A P-band SAR interference filter (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: The synthetic aperture radar (SAR) interference filter is an adaptive filter designed to reduce the effects of interference while minimizing the introduction of undesirable side effects. The author examines the adaptive spectral filter and the improvement in processed SAR imagery using this filter for Jet Propulsion Laboratory Airborne SAR (JPL AIRSAR) data. The quality of these improvements is determined through several data fidelity criteria, such as point-target impulse response, equivalent number of looks, SNR, and polarization signatures. These parameters are used to characterize two data sets, both before and after filtering. The first data set consists of data with the interference present in the original signal, and the second set consists of clean data which has been coherently injected with interference acquired from another scene.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 401-403.
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    SAR processing based on the exact two-dimensional transfer function (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: The two-dimensional transfer functions of several synthetic aperture radar (SAR) focusing algorithms are derived considering the spaceborne SAR environments. The formulation includes the factors of the earth rotation and the antenna squint angles. The resultant transfer functions are explicitly expressed in terms of Doppler centroid frequency and Doppler frequency rate, which can be accurately estimated from the SAR data. Point target simulation results show that the algorithm based on the two-dimensional Fourier transformation outperforms the one-dimensional one for processing data acquired from high squint angles. The two-dimensional Fourier transformation approach appears to be a viable and simple solution for the processor design of future spaceborne SAR systems.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 355-359.
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    Development of soil moisture retrieval algorithm for L-band SAR measurements (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: A study of algorithm development and testing for soil moisture retrieval for bare fields using L-band synthetic aperture radar (SAR) imagery is reported. First-order surface scattering models predict that the copolarization ratio is sensitive to soil moisture but not to surface roughness. All possible ratios of the co-polarization signals and their linear combinations are evaluated. The best sensitivity to soil moisture is achieved from measurements as predicted by the first-order surface scattering model. The effects of system noise and volume scattering of soil are evaluated. To minimize the effect of the volume scattering, an algorithm which includes both the surface and volume scattering has been developed and tested using Jet Propulsion Laboratory Airborne SAR (JPL AIRSAR) data. The results show that the estimation of soil moisture can be improved after removing the system noise and including the volume scattering effect at large incidence angles.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 495-497.
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    Soil moisture verification study of the ESTAR microwave radiometer - Walnut Gulch, AZ 1991 (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: The application of an electronically steered thinned array L-band radiometer (ESTAR) for soil moisture mapping is investigated over the arid rangeland Walnut Gulch Watershed. Antecedent rainfall and evaporation for the flights are very different and result in a wide range of soil moisture conditions. The high spatial variability of rainfall events within this region results in moisture conditions with dramatic spatial patterns. Sensor performance is verified using two approaches. Microwave data are used in conjunction with a microwave emission model to predict soil moisture. These predictions are compared to ground observations of soil moisture. A second verification is possible using an extensive data set. Both tests showed that the ESTAR is capable of providing soil moisture with the same level of accuracy as existing systems.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 486-488.
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    Improved instrumentation for monitoring the diurnal and seasonal cycles in the dielectric properties of forest canopies (1992)
    In:  Other Sources
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    Publikationsdatum: 2011-08-24
    Beschreibung: The design and implementation of a dielectric measurement system that facilitates the automated and continuous in situ monitoring of the dielectric properties of several canopy constituents is presented. This system utilizes the same coaxial line reflection coefficient measurement technique as the portable dielectric probe (PDP) while incorporating several features that facilitate the automated monitoring of canopy dielectric properties. The new system is capable of continuously monitoring the dielectric properties of the canopy constituents in a near-simultaneous fashion. The implementation of a data logger as a user interface has increased the number of measurements that the instrument is able to store in memory while significantly improving system reliability.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: IGARSS '92; Proceedings of the 12th Annual International Geoscience and Remote Sensing Symposium, Houston, TX, May 26-29, 1992. Vol. 1 (A93-47551 20-43); p. 425-427.
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