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  • 1
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    Optical transients and depth analysis (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Flaws of the depth analysis technique of distinguishing photographic plate defects are discussed. The method is shown to be unreliable in confirming or disproving the astrophysical nature of optical transients. The arguments of Greiner and of Zytkow to the contrary are criticized.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Gamma-ray bursts - Observations, analyses and theories (A93-20206 06-90); p. 133-137.
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  • 2
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    Active structural control for damping augmentation and compensation of thermal distortion (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A large space-based Focus Mission Interferometer is used as a testbed for the NASA Controls and Structures Interaction Program. Impedance-based adaptive structural control and control of thermal disturbances are demonstrated using an end-to-end simulation of the system's optical performance. Attention is also given to integrated optical/structural modeling and a hierarchical, layered control strategy.
    Schlagwort(e): CYBERNETICS
    Materialart: Journal of Intelligent Material Systems and Structures (ISSN 1045-389X); 3; 4; p. 668-679.
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  • 3
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    Covariance of biophysical data with digital topograpic and land use maps over the FIFE site (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: This paper discusses the biophysical stratification of the FIFE site, implementation of the stratification utilizing geographic information system methods, and validation of the stratification with respect to field measurements of biomass, Bowen ratio, soil moisture, and the greenness vegetation index (GVI) derived from TM satellite data. Maps of burning and topographic position were significantly associated with variation in GVI, biomass, and Bowen ratio. The stratified design did not significantly alter the estimated site-wide means for surface climate parameters but accounted for between 25 and 45 percent of the sample variance depending on the variable.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 97; D17; p. 19,009-19,021.
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  • 4
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    Active and passive microwave measurements of soil moisture in FIFE (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: During the intensive field campaigns of the First International Satellite Land Surface Climatology Project (ISLSCP) Field Experiment (FIFE) in May-October of 1987, several nearly simultaneous measurements were made with low-altitude flights of the L-band radiometer and C- and X-band scatterometers over two transects in the Konza Prairie Natural Research Area, some 8 km south of Manhattan, Kansas. These measurements showed that although the scatterometers were sensitive to soil moisture variations in most regions under the flight path, the L-band radiometer lost most of its sensitivity in regions unburned for many years. The correlation coefficient derived from the regression between the radar backscattering coefficient and the soil moisture was found to improve with the increase in antenna incidence angle. This is attributed to a steeper falloff of the backscattering coefficient as a function of local incidence at angles near nadir than at angles greater than 30 deg.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: Journal of Geophysical Research (ISSN 0148-0227); 97; D17; p. 18,979-18,985.
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  • 5
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    Clustering methods for removing outliers from vision-based range estimates (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The present approach to the automation of helicopter low-altitude flight uses one or more passive imaging sensors to extract environmental obstacle information; this is then processed via computer-vision techniques to yield a time-varying map of range to obstacles in the sensor's field of view along the vehicle's flight path. Attention is given to two related techniques which can eliminate outliers from a sparse range map, clustering sparse range-map information into different spatial classes that rely on a segmented and labeled image to aid in spatial classification within the image plane.
    Schlagwort(e): CYBERNETICS
    Materialart: In: Intelligent robots and computer vision X: Neural, biological, and 3-D methods; Proceedings of the Meeting, Boston, MA, Nov. 14, 15, 1991 (A93-51646 22-63); p. 326-337.
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  • 6
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    L-band radar scattering from grass (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A radar system based on a network analyzer has been developed to study the backscatter from vegetation. The radar is operated at L-band. Radar measurements of a grass field were made in 1991. The radar returns from the grass were measured at three incidence angles. Ground truth and canopy parameters such as blade and stem dimensions, moisture content of the grass and the soil, and blade and stem density, were measured. These parameters are used in a distorted Born approximation model to compute the backscatter coefficients from the grass layer. The model results are compared with the radar 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. 1754-1757.
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  • 7
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    Direction angle sensitivity of agricultural field backscatter with Airsar data (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The direction angle sensitivity of agricultural field backscatter is studied. The direction angle is defined as the angle between the incident plane and the perpendicular to the row direction. Maximum backscatter power from an angricultural field is expected to occur when the furrow induced slopes are oriented towards the radar, i.e., for a 0 deg direction angle. This effect is known as the cardinal effect. Because of the way the looks are formed in the NASA/JPL airborne synthetic aperture radar (AIRSAR) processor, each look corresponds to a slightly different squint angle. This provides a unique data set to analyze the cardinal effect, as it allows simultaneous observations of the backscatter of a field for sixteen different direction angles. The backscatter variations of the agricultural fields with direction angle at P-, L-, and C-bands is described. The observed variations in backscatter are compared with model predictions. The model predicts that the maximum backscatter occurs for a 0 deg direction angle, but underestimates the backscatter variations with direction angle by more than 10 dB.
    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. 1680-1682.
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  • 8
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    Polarimetric and multifrequency SAR signatures of wet snow (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: C-, L-, and P-band polarimetric signatures of wet snow surfaces have been analyzed, based on airborne synthetic aperture radar (AIRSAR) surveys of an Alpine test site. The importance of surface roughness is evident in the C- and L-band signatures, whereas the diffuse scattering contribution by internal inhomogeneities in the snowpack increases from the C- to the P-band at incidence angles below 50 deg due to increasing penetration.
    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. 1658-1660.
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  • 9
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    Dual baseline and frequency along-track interferometry (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The Jet Propulsion Laboratory (JPL) airborne synthetic aperture radar (AIRSAR) L-band along-track interferometer images currents and waves on the ocean surface. By modifying the operating procedure of this two antenna interferometer, a technique has been developed to enable interferometric measurements to be made simultaneously at two different baselines. The availability of such data allows measurement of the decorrelation process of the ocean in greater detail. The coherence time of the ocean surface can be measured at high resolution over large areas. In addition to the L-band interferometer, a C-band along-track interferometer has been developed. It allows C-band dual-baseline measurements to be made simultaneous with the L-band measurements. The dual-baseline technique and AIRSAR implementation are described, and some example data 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. 1585-1588.
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  • 10
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    Parameterization of surface heat fluxes above a forest with satellite thermal sensing (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The authors discuss the feasibility of determining the surface flux of sensible heat from forests with surface temperatures measured by satellites together with temperature soundings in the unstable atmospheric boundary layer (ABL). The latent heat flux is derived from the sensible heat flux by means of the energy budget. The study makes use of data collected during HAPEX-MOBILHY (Hydrologic Atmospheric Pilot Experiment-Modelization du Bilan Hydrique). The methodology is based on turbulence similarity for the unstable ABL. The surface temperature data were derived from measurements by the advanced very high resolution radiometer (AVHRR) aboard the NOAA-9 satellite; the atmospheric profiles were obtained by radiosondes.
    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. 1505-1507.
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  • 11
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    Estimation of photosynthetic capacity using polarization (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The authors examine the hypothesis that some part of the ecosystem-dependent variability of the vegetation indices is attributable to the effects of specular reflection of sunlight by leaves. A new class of vegetation indices, or 'minus specular' vegetation indices, is defined to account for the effects of specularly reflected light. Results show that the 'minus specular' indices, when compared to the traditional vegetation indices, potentially provide better estimates of the photosynthetic activity of a canopy than the traditional vegetation indices, particularly as a function of sun and view 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. 2 (A93-47551 20-43); p. 1471-1473.
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  • 12
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    SAYANI'91 - A joint United States/Commonwealth of Independent States field campaign to investigate forest decline damage in the Krasnoyarsk region of southcentral Siberia (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The field experiment described took place in the Sayani Mountains of Siberia. The purpose of the joint field campaign was to observe and exchange methodologies with Russian scientists with regard to the development of remote sensing techniques for the early detection and assessment of forest decline damage believed to be associated with atmospheric deposition and/or insect and disease infestations. Several types of passive and active remote sensing measurements were made in conjunction with biophysical measurements on vegetative samples collected from four study sites representing a strong elevational gradient. Relatively cloud-free SPOT data were also acquired over the study area. Moderate canopy damage was recorded at the mid-elevation site (3400 ft/1037 m). The lowest levels of damage were recorded at the lowest elevation site (2300 ft/701 m.) At all sites, east versus west flagging of the canopy was noted (i.e., full canopy on the west-facing side of the canopy, significantly less foliage on the east-facing side).
    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. 1286-1288.
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  • 13
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    Ice patterns and hydrothermal plumes, Lake Baikal, Russia - Insights from Space Shuttle hand-held photography (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Earth photography from the Space Shuttle is used to examine the ice cover on Lake Baikal and correlate the patterns of weakened and melting ice with known hydrothermal areas in the Siberian lake. Particular zones of melted and broken ice may be surface expressions of elevated heat flow in Lake Baikal. The possibility is explored that hydrothermal vents can introduce local convective upwelling and disrupt a stable water column to the extent that the melt zones which are observed in the lake's ice cover are produced. A heat flow map and photographs of the lake are overlaid to compare specific areas of thinned or broken ice with the hot spots. The regions of known hydrothermal activity and high heat flow correlate extremely well with circular regions of thinned ice, and zones of broken and recrystallized ice. Local and regional climate data and other sources of warm water, such as river inlets, are 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. 1559-1561.
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  • 14
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    Estimation of effective aerodynamic roughness with altimeter measurements (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A new method is presented for estimating the aerodynamic roughness length of heterogeneous land surfaces and complex landscapes using elevation measurements performed with an airborne laser altimeter and the Seasat radar altimeter. Land surface structure is characterized at increasing length scales by considering three basic landscape elements: (1) partial to complete canopies of herbaceous vegetation; (2) sparse obstacles (e.g., shrubs and trees); and (3) local relief. Measured parameters of land surface geometry are combined to obtain an effective aerodynamic roughness length which parameterizes the total atmosphere-land surface stress.
    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. 1508-1510.
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  • 15
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    Refining image segmentation by integration of edge and region data (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: An iterative parallel region growing (IPRG) algorithm previously developed by Tilton (1989) produces hierarchical segmentations of images from finer to coarser resolution. An ideal segmentation does not always correspond to one single iteration but to several different ones, each one producing the 'best' result for a separate part of the image. With the goal of finding this ideal segmentation, the results of the IPRG algorithm are refined by utilizing some additional information, such as edge features, and by interpreting the tree of hierarchical regions.
    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. 1406-1408.
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  • 16
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    Comparison of measurements and theory for backscatter from vegetation-covered soil on the Konza prairie (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Radar backscatter measurements over the Konza Prairie were obtained by means of C- and X-band scatterometers as a part of the first ISLSCP Field Experiment (FIFE) to determine soil moisture. Nearly simultaneous radar and radiometer data sets were collected along two transects that coincided with direct soil-moisture measurements. The results show that radars can be used for soil-moisture estimation over the complete transect, whereas radiometer sensitivity to soil moisture is drastically reduced over regions left unburned for many years. A combined rough-surface/volume scatter model was formulated. Calculated and measured scattering data are compared to determine the sensitivity of the scattering coefficient to different surface treatments.
    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. 920-922.
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  • 17
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    Alaska SAR processor implementation of E-ERS-1 (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The synthetic aperture radar (SAR) data processing algorithm used by the Alaska SAR Facility (ASF) for the European Space Agency's first Remote-Sensing Satellite (E-ERS-1) SAR data are examined. Preprocessing highlights two features: signal measurement, which includes signal-to-noise ratio, replica measurement, and noise measurement; and Doppler measurement, which includes clutter lock and autofocus. The custom pipeline architecture performs the main processing with controls at the input interface, range correlator, corner-turn memory, azimuth correlator, and multi-look memory. The control software employs a flexible control scheme. The Committee on Earth Observation Satellites (CEOS) format encapsulates the ASF products. System performance for SAR image processing of E-ERS-1 data is reviewed.
    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. 599-602.
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  • 18
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    Potential of long-baseline infrared interferometry for narrow-angle astrometry (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Narrow-angle astrometry has many astrophysical applications, from the measurement of parallaxes to the search for planets around nearby stars. Ground-based long-focus telescopes with photoelectric detectors have achieved accuracies of about 2-3 milliarcsec in 1 h. This accuracy is limited primarily by the atmosphere, and is consistent with models of atmospheric turbulence. However, applying these turbulence models to observations with long-baseline interferometers yields astrometric errors that are far smaller than can be achieved with long-focus telescopes. The predictions for the ultimate accuracy of ground-based narrow-angle astrometry using long-baseline IR (2.2 micron) stellar interferometers are very promising. With the excellent seeing at a high altitude site like Mauna Kea, the atmospheric limit for a 1 h astrometric measurement is expected to be of the order of 10 microarcsec for 1 h of integration. This two-order-of-magnitude improvement over conventional measurements is due to two effects. One is that a long-baseline IR interferometer can find useful reference stars very near an arbitrary target star, so that the atmospherically-induced motions of both stars are highly correlated. The second is that the baseline length can be much larger than the separation of the stellar beams in the turbulent atmosphere, resulting in a reduction in astrometric error with increasing baseline length.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 262; 1; p. 353-358.
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  • 19
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    Developing technologies for lunar-based astronomy (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Prospects for lunar-based astronomy and the development of the required technologies are briefly reviewed. A systematic approach to lunar-based astronomy includes a progression in capability from small automated telescopes to the 16-meter reflector on the moon. A next step beyond the 16-meter reflector will be a Lunar Optical/Ultraviolet/Infrared Synthesis Array. Intermediate steps are represented by the Lunar Transit Telescope and the Lunar Cluster Telescope Experiment. Priorities for the required technology development are identified.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Engineering, construction, and operations in space III: Space '92; Proceedings of the 3rd International Conference, Denver, CO, May 31-June 4, 1992. Vol. 2 (A93-41976 17-12); p. 1853-1864.
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  • 20
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    System concepts for a series of lunar optical telescopes (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The Lunar Telescope Working Group of the Marshall Space Flight Center, NASA, has conducted conceptual studies of an evolutionary family of UV/ optical/IR telescopes to be based on the lunar surface. Included are: (1) the 16-m aperture Large Lunar Telescope; (2) the 4-m aperture precursor Lunar Cluster Telescope Experiment; and (3) the 2-m Lunar Transit Telescope proposed by John McGraw of the Steward Observatory. Development and emplacement of these advanced astronomical facilities would parallel the buildup of an initial lunar exploration site, an early lunar outpost, and a permanent lunar base. The Working Group has examined the feasibility of constructing such telescopes and assessed technology, subsystem, system, transportation, and operations requirements for their development and emplacement. Influences of the lunar environment and site selection on telescope design and operation were also evaluated.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Engineering, construction, and operations in space III: Space '92; Proceedings of the 3rd International Conference, Denver, CO, May 31-June 4, 1992. Vol. 2 (A93-41976 17-12); p. 1809-1831.
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  • 21
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    Plot-scale field experiment of surface hydrologic processes with EOS implications (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Plot-scale hydrologic field studies were initiated at NASA Marshall Space Flight Center to a) investigate the spatial and temporal variability of surface and subsurface hydrologic processes, particularly as affected by vegetation, and b) develop experimental techniques and associated instrumentation methodology to study hydrologic processes at increasingly large spatial scales. About 150 instruments, most of which are remotely operated, have been installed at the field site to monitor ground atmospheric conditions, precipitation, interception, soil-water status, and energy flux. This paper describes the nature of the field experiment, instrumentation and sampling rationale, and presents preliminary findings.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: Engineering, construction, and operations in space - III: Space '92; Proceedings of the 3rd International Conference, Denver, CO, May 31-June 4, 1992. Vol. 2 (A93-41976 17-12); p. 2082-2093.
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  • 22
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    BATSE's sky sensitivity map (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The Burst and Transient Source Experiment (BATSE) detects any gamma-ray burst not obscured by the earth and intense enough to produce a sufficiently strong signal in at least two of its eight large area NaI detectors (LADs). For a given intensity, a LAD records a stronger signal from a source which directly faces it than from a source to its side. Thus, BATSE's detection of a gamma-ray burst may depend upon the burst's direction. We discuss the effect of this uneven exposure to the sky on the instrument's measurement of the distribution of gamma-ray burst directions and intensities, and we describe our method of accounting for the effect.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Gamma-ray bursts; Proceedings of the Workshop, Univ. of Alabama, Huntsville, Oct. 16-18, 1991 (A93-40051 16-93); p. 399-403.
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  • 23
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    The Germanium GAlactic Plane Patrol mission (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The goal of the Germanium GAlactic Plane Patrol mission (GGAPP) is to provide a continuous monitor of the Galactic Plane (GP) for variable sources of gamma-ray lines. Potentially interesting sources include black hole candidates, X-ray binary systems, pulsars, gamma-ray bursts, and solar flares. The GGAPP instrument is an array of Ge detectors cooled by a mechanical refrigerator to achieve a spectral resolution of 2 keV at 1 MeV (1/500). A bismuth germanate (BGO) shield will restrict the field-of-view (FOV) to within 20 deg of the GP, and a modulation collimator system will locate strong sources to less than 0.3 deg in galactic longitude, provide a direct means of subtracting background, and mapping the diffuse emission from the GP. The spacecraft will be rotationally stabilized with the spin axis perpendicular to the GP such that the modulator scans in galactic longitude. A HEO or L1 orbit will keep GGAPP far away from the strong background produced by the Earth. GGAPP will provide a natural bridge between GRO and future missions such as INTEGRAL/NAE.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Gamma-ray bursts; Proceedings of the Workshop, Univ. of Alabama, Huntsville, Oct. 16-18, 1991 (A93-40051 16-93); p. 390-394.
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  • 24
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    Preliminary results of a Monte Carlo simulation of burst directions by BATSE (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The effect of varying BATSE trigger parameters on the modeled BATSE detection rate is investigated numerically. Quantitative estimates are obtained of the systematic effects generated by the complex interplay of trigger times, variations in the signal-to-noise ratio for burst detection as well as the time scale over which backgrounds are determined, and the number of required detections above threshold. It is found, in particular that employing a third detection, at a reduced signal-to-noise ratio, to resolve a burst does not increase the detection rate. It is also shown that the BATSE detection rate is insensitive to variations in the time scale over which the background is determined.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Gamma-ray bursts; Proceedings of the Workshop, Univ. of Alabama, Huntsville, Oct. 16-18, 1991 (A93-40051 16-93); p. 388, 389.
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  • 25
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    Gamma-ray burst locations from the Burst and Transient Source Experiment (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The Burst and Transient Source Experiment (BATSE) consists of eight anisotropic gamma-ray spectrometers at the corners of the Compton Gamma Ray Observatory. BATSE monitors the full sky from a fixed orientation and determines the direction of gamma-ray bursts with an accuracy appropriate for studying the bursts' celestial distribution. We describe the calculation of gamma-ray burst directions from measurements made by BATSE. We present a sample of calculated directions from BATSE's measurement of solar flaxes and compare the calculated directions with the solar direction. We describe the systematic errors apparent in these data and discuss ongoing efforts to correct them.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Gamma-ray bursts; Proceedings of the Workshop, Univ. of Alabama, Huntsville, Oct. 16-18, 1991 (A93-40051 16-93); p. 383-387.
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  • 26
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    Search for time-correlated optical flashes of GRO-detected gamma-ray bursts (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: This status report presents some details on the project 'Search for time-correlated optical counterparts of gamma-ray bursters'. The photographic sky patrol of the three observatories Sonneberg (FRG), Ondrejov (CSFR), and Odessa (USSR) is used to look for patrol plates which have been exposed simultaneously with a gamma-ray burst detected by GRO. Our expectations and the very first results are presented.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Gamma-ray bursts; Proceedings of the Workshop, Univ. of Alabama, Huntsville, Oct. 16-18, 1991 (A93-40051 16-93); p. 327-331.
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  • 27
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    The Multi-Spectral Solar Telescope Array. II - Soft X-ray/EUV reflectivity of the multilayer mirrors (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: We have developed seven compact soft X-ray/EUV (XUV) multilayer coated and two compact FUV interference film coated Cassegrain and Ritchey-Chretien telescopes for a rocket borne observatory, the Multi-Spectral Solar Telescope Array. We report here on extensive measurements of the efficiency and spectral bandpass of the XUV telescopes carried out at the Stanford Synchrotron Radiation Laboratory.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Multilayer and grazing incidence X-ray(EUV optics; Proceedings of the Meeting, San Diego, CA, July 22-24, 1991 (A93-39658 15-74); p. 432-445.
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  • 28
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    The High Resolution Telescope Cluster. I - Overview and technical status (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A major component of the Advanced Solar Observatory is the High Resolution Telescope Cluster (HRTC) for investigations of the solar atmosphere at soft X-ray, XUV, EUV, and VUV wavelengths, via high resolution spectroheliograms in lines and continuum emitted over the full, (4500 to 100,000,000 K) range of temperatures of the outer solar atmosphere; angular resolution may be as high as 0.03 arcsec. An analysis is conducted of a model HRTC instrument complement encompassing a 60-90 cm aperture VUV telescope, a 40-50 cm aperture EUV telescope, three 40-50 cm aperture XUV telescopes, and a 40-cm aperture soft X-ray telescope, as well as flare spectrometers and polarimeters and four coronagraph/spectrographs.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Multilayer and grazing incidence X-ray(EUV optics; Proceedings of the Meeting, San Diego, CA, July 22-24, 1991 (A93-39658 15-74); p. 353-369.
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  • 29
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    The Solar/Stellar Coronal Explorer and the Solar/Stellar Coronal Observatory (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The Solar/Stellar Coronal Explorer (SSCE) carries six identical Ritchey-Chretien Telescopes of 127 mm aperture each; their images will be recorded by multianode microchannel-array detectors. The mirrors of five of the telescopes are coated with multilayer reflecting structures that select narrow XUV wavelength bands corresponding to strong emission lines emitted by solar or stellar coronal plasmas. Also noted here is a larger explorer mission concept, that of the Solar/Stellar Coronal Observatory, which will undertake more extensive spectroscopic observations.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Multilayer and grazing incidence X-ray(EUV optics; Proceedings of the Meeting, San Diego, CA, July 22-24, 1991 (A93-39658 15-74); p. 281-295.
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  • 30
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    The Ultra High Resolution XUV Spectroheliograph. III - A modified configuration for a free flying platform (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The Ultra-High Resolution XUV Spectroheliograph (UHRXS) is a comprehensive solar observatory capable of studying solar phenomena at soft X-ray, XUV, EUV, and VUV wavelengths with normal incidence imaging multilayer telescopes capable of very high angular resolution (about 0.1 arcsec), and spectrographs able to achieve high spectral resolution. This instrument has been selected by NASA for flight as an attached payload on the Space Station Freedom. Recent developments have made it clear that accommodations for attached payloads on Freedom will not become available during the initial operations of Freedom and may never be available. We have studied the changes that must be made to place the UHRXS instrument on a Free Flying Plafform such as the Delta Launched Explorer Bus. We report on the configuration, performance, and accommodation on a free flying platform of the revised UHRXS concept.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Multilayer and grazing incidence X-ray(EUV optics; Proceedings of the Meeting, San Diego, CA, July 22-24, 1991 (A93-39658 15-74); p. 265-280.
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  • 31
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    Solar observations with the Multi-Spectral Solar Telescope Array (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The Multi-Spectral Solar Telescope Array (MSSTA) is a sounding rocket-borne solar observatory which was succesfully launched on May 13, 1991, from the White Sands Missile Range, NM. Ultrahigh resolution, full-disk solar X-ray, EUV, and FUV images were obtained with the MSSTA Herschelian, Cassegrain, and Ritchey-Chretien telescopes. We describe the payload and provide some preliminary scientific results from the flight.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Multilayer and grazing incidence X-ray(EUV optics; Proceedings of the Meeting, San Diego, CA, July 22-24, 1991 (A93-39658 15-74); p. 175-187.
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  • 32
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    In-flight performance of the Broad-Band X-Ray Telescope (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The Broad-Band X-Ray Telescope (BBXRT) was designed to carry out moderate resolution spectrophotometry of cosmic X-ray sources in the 0.3-12 keV band from the Space Shuttle. It consists of a pair of coaligned conical foil telescopes, with cryogenically cooled Si(Li) spectrometers as focal instruments. It was flown as part of the Astro-1 mission in December, 1990. The in-flight performance of the instrument was essentially as predicted on the basis of ground calibration and modelling. We discuss the performance of the system, with emphasis on the conical mirror systems, and present some preliminary scientific results which illustrate the power of broad band, high sensitivity X-ray spectrophotometry.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Multilayer and grazing incidence X-ray(EUV optics; Proceedings of the Meeting, San Diego, CA, July 22-24, 1991 (A93-39658 15-74); p. 72-81.
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  • 33
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    Identification of linear multivariable systems by identification of observers with assigned real eigenvalues (1992)
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    Publikationsdatum: 2011-08-24
    Schlagwort(e): CYBERNETICS
    Materialart: Journal of the Astronautical Sciences (ISSN 0021-9142); 40; 2; p. 261-279.
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  • 34
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    Enhancing images with Intensity-Dependent Spread functions (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The theory of Intensity-Dependent Spread functions (IDS), a model of the human visual system proposed by Cornsweet (1985), is applied to image enhancement. An artificial image is examined which illustrates the characteristics of IDS processing and shows how the theoretical results translate into visual effects. Examples of realistic scenes that have been enhanced by IDS are presented. The system is shown to be particularly useful for bringing out detail in regions of low-contrast images. IDS can be readily implemented on a parallel computer.
    Schlagwort(e): CYBERNETICS
    Materialart: In: Human vision, visual processing, and digital display III; Proceedings of the Meeting, San Jose, CA, Feb. 10-13, 1992 (A93-33438 12-63); p. 253-264.
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  • 35
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    Studies of temporal change using radar interferometry (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Decorrelation of the radar signals with time, which is indicative of changes in the surface occurring during the period of time spanned by the images, is examined. It is concluded that the decorrelation effects due to thermal noise can be easily evaluated and removed, while those due to slight angular changes between flight tracks are negligible. Spatial baseline and rotation-induced decorrelation can be derived using the Fourier transform of the impulse response intensity, and increases linearly with baseline or rotation in an ideal system. Empirical results confirm that as the baseline increases, the overall correlation decreases due to spatial baseline noise.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: Synthetic aperture radar; Proceedings of the Meeting, Los Angeles, CA, Jan. 20, 21, 1992 (A93-32508 12-32); p. 187-198.
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  • 36
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    Using calibrated SAR data (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A number of approaches for calibrating SAR imaging data including data from multipolarization and multifrequency systems developed at the Jet Propulsion Laboratory are discussed. It is shown how calibrated SAR data can be used to improve the understanding of the physical properties of the earth's surface layer and how calibration uncertainties and system noise should be handled by the SAR data user. Examples of calibrated SAR data from the NASA/JPL DC-8 SAR are used to demonstrate use of calibrated data to monitor temporal change and to improve the classification of land cover type.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: In: Synthetic aperture radar; Proceedings of the Meeting, Los Angeles, CA, Jan. 20, 21, 1992 (A93-32508 12-32); p. 224-234.
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  • 37
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    Coordination of multiwavelength groundbased and satellite observations of novae in outburst (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Observational data on novae in outburst are reviewed, focusing on the information gained from ultraviolet spectroscopy. Topics discussed include a brief taxonomy of novae, the theoretical framework, observational diagnostics of the outburst, IUE satellite observations, and future trends in novae observations at many wavelengths using space-based observatories to augment the work of ground-based observers.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Variable star research: An international perspective (A93-29397 10-89); p. 290-301.
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  • 38
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    Using qualitative maps to direct reactive robots (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The principal advantage of mobile robots is that they are able to go to specific locations to perform useful tasks rather than have the tasks brought to them. It is important therefore that the robot be used to reach desired locations efficiently and reliably. A mobile robot whose environment extends significantly beyond its sensory horizon must maintain a representation of the environment, a map, in order to attain these efficiency and reliability requirements. We believe that qualitative mapping methods provide useful and robust representation schemes and that such maps may be used to direct the actions of a reactively controlled robot. In this paper we describe our experience in employing qualitative maps to direct, through the selection of desired control strategies, a reactive-behavior based robot. This mapping capability represents the development of one aspect of a successful deliberative/reactive hybrid control architecture.
    Schlagwort(e): CYBERNETICS
    Materialart: In: Cooperative intelligent robotics in space III; Proceedings of the Meeting, Boston, MA, Nov. 16-18, 1992 (A93-29101 10-54); p. 262-273.
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  • 39
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    Automatic target recognition using a feature-based optical neural network (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: An optical neural network based upon the Neocognitron paradigm (K. Fukushima et al. 1983) is introduced. A novel aspect of the architectural design is shift-invariant multichannel Fourier optical correlation within each processing layer. Multilayer processing is achieved by iteratively feeding back the output of the feature correlator to the input spatial light modulator and updating the Fourier filters. By training the neural net with characteristic features extracted from the target images, successful pattern recognition with intra-class fault tolerance and inter-class discrimination is achieved. A detailed system description is provided. Experimental demonstration of a two-layer neural network for space objects discrimination is also presented.
    Schlagwort(e): CYBERNETICS
    Materialart: In: Optical pattern recognition III; Proceedings of the Meeting, Orlando, FL, Apr. 21, 22, 1992 (A93-28672 10-63); p. 276-282.
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  • 40
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    Optical processing for range and attitude determination (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A rugged, miniaturized, optical cross-correlator that recognizes a single object is particularly suitable for performing a single-vision function, such as pattern recognition for semi-autonomous navigation, landing, and docking of vehicles to a pre-designated landing mark. The optical cross-correlator, with a video input from a simple imaging system and the output of the optical correlation plane processed using the standard star tracker software, produces sufficient information for a spacecraft's terminal homing navigation system to complete a docking maneuver.
    Schlagwort(e): CYBERNETICS
    Materialart: In: Sensors and sensor systems for guidance and navigation II; Proceedings of the Meeting, Orlando, FL, Apr. 22, 23, 1992 (A93-28151 10-35); p. 23-28.
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  • 41
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    Survival of falling robots (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: As mobile robots are used in more uncertain and dangerous environments, it will become important to design them so that they can survive falls. In this paper, we examine a number of mechanisms and strategies that animals use to withstand these potentially catastrophic events and extend them to the design of robots. A brief survey of several aspects of how common cats survive falls provides an understanding of the issues involved in preventing traumatic injury during a falling event. After outlining situations in which robots might fall, a number of factors affecting their survival are described. From this background, several robot design guidelines are derived. These include recommendations for the physical structure of the robot as well as requirements for the robot control architecture. A control architecture is proposed based on reactive control techniques and action-oriented perception that is geared to support this form of survival behavior.
    Schlagwort(e): CYBERNETICS
    Materialart: In: Mobile robots VI; Proceedings of the Meeting, Boston, MA, Nov. 14, 15, 1991 (A93-53170 23-63); p. 91-102.
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  • 42
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    Measurement and calibration of static distortion of position data from 3D trackers (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Three-dimensional trackers are becoming increasingly important as user inputs in interactive computer systems. These trackers output the three-dimensional position, and often the orientation, of a sensor in space. The three-dimensional tracking is often, however, highly distorted and inaccurate. The purpose of this paper is to discuss methods for the measurement and characterization of the static distortion of the position data. When the distortion is constant, various methods can be used to calibrate the data from the tracker to increase accuracy. Several preliminary methods are discussed in this paper, including polynomial and weighted lookup methods. The measurement and calibration methods are applied to the Polhemus electromagnetic tracking system, but are applicable to tracking systems based on other technologies.
    Schlagwort(e): CYBERNETICS
    Materialart: In: Stereoscopic displays and applications III; Proceedings of the Meeting, San Jose, CA, Feb. 12, 13, 1992 (A93-53119 23-54); p. 244-255.
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  • 43
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    Geologic process studies using Synthetic Aperture Radar (SAR) data (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The use of SAR data to study geologic processes for better understanding of recent tectonic activity and climate change as well as the mitigation of geologic hazards and exploration for nonrenewable resources is discussed. The geologic processes that are particularly amenable to SAR-based data include volcanism; soil erosion, degradation, and redistribution; coastal erosion and inundation; glacier fluctuations; permafrost; and crustal motions. When SAR data are combined with data from other planned spaceborne sensors including ESA ERS, the Japanese Earth Resources Satellite, and the Canadian Radarsat, it will be possible to build a time-series view of temporal changes over many regions of earth.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: Episodes (ISSN 0705-3797); 15; 1; p. 21-31.
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    Measurement of subresolution terrain displacements using SPOT panchromatic imagery (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: SPOT panchromatic imagery is used to measure subresolution horizontal terrain displacements that are associated with earthquakes, sand dune migration, coastal processes, and glacial motion. The approach is aimed at detecting and measuring surface processes by statistically matching the radiometric patterns in the data that differ spatially in a consistent direction over many pixels. Data obtained from the satellite-derived imagery can facilitate the understanding of natural hazards and the determination of the rates of many environmental processes worldwide.
    Schlagwort(e): EARTH RESOURCES AND REMOTE SENSING
    Materialart: Episodes (ISSN 0705-3797); 15; 1; p. 56-61.
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  • 45
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    Automated absolute phase retrieval in across-track interferometry (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Discussed is a key element in the processing of topographic radar maps acquired by the NASA/JPL airborne synthetic aperture radar configured as an across-track interferometer (TOPSAR). TOPSAR utilizes a single transmit and two receive antennas; the three-dimensional target location is determined by triangulation based on a known baseline and two measured slant ranges. The slant range difference is determined very accurately from the phase difference between the signals received by the two antennas. This phase is measured modulo 2pi, whereas it is the absolute phase which relates directly to the difference in slant range. It is shown that splitting the range bandwidth into two subbands in the processor and processing each individually allows for the absolute phase. The underlying principles and system errors which must be considered are discussed, together with the implementation and results from processing data acquired during the summer of 1991.
    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. 1582-1584.
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  • 46
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    Albedo patterns and gypsum generation in the central Namib Desert - Land, sea and air interactions on an arid West Coast (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: In the central Namib Desert, dune-free surfaces are separated abruptly from a sea of yellow and red sand dunes at the Kuiseb River canyon. The off-white hues of the dune-free area result from anomalously high surficial gypsum enrichment. Satellite imagery indicates that the gypsum surfaces are associated with lower surface maximum temperatures than those of the darker dune surfaces to the south. One of various sources of sulfate for the gypsum bodies is oceanic H2S, supplied to desert land-surfaces by regular fog incursions. Since fog events are widespread along the coast, the question of anomalous gypsum accumulations north of the dune sea arises. Satellite imagery, in conjunction with more detailed handheld photography from the space shuttle, indicates that the penetration of fog inland is significantly greater over the gypsum surfaces than it is over the dunes. It is postulated that the thermal gradient between these surfaces generates a heat low centered over the northern part of dune sea and that this enhances fog and H2S advection on its north side onto the nearby dune-free zone. In such a system, gypsum/caliche surfaces reinforce advection of fog over themselves in a positive feedback mode.
    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. 1565-1567.
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    Radiometric gains of satellite sensors of reflected solar radiation - Results from NASA ER-2 aircraft measurements (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A method for using congruent aircraft-satellite observations to calibrate a satellite sensor is presented. A calibrated spectroradiometer at an altitude of 19 km above White Sands, NM, is oriented to view White Sands at the satellite overpass time along the same view vector as the satellite sensor. Collected data are transformed into corresponding estimates of sensor band radiance at the satellite (derived from the aircraft measurements), and average count (from the sensor measurements). These are both averaged across the footprint of the spectroradiometer. Results are presented for the evolution of NOAA-11 Advanced Very High Resolution Radiometer (AVHRR) (Bands 1 and 2) gain between November 1988 and October 1990, and for GOES-6 and GOES-7 VISSR/VAS visible bands during the same period. Estimates of uncertainty in the results are presented, as well as ideas for their reduction in future flights.
    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. 802-805.
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    LAI inversion from optical reflectance using a neural network trained with a multiple scattering model (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The inversion of the leaf area index (LAI) canopy parameter from optical spectral reflectance measurements is obtained using a backpropagation artificial neural network trained using input-output pairs generated by a multiple scattering reflectance model. The problem of LAI estimation over sparse canopies (LAI 〈 1.0) with varying soil reflectance backgrounds is particularly difficult. Standard multiple regression methods applied to canopies within a single homogeneous soil type yield good results but perform unacceptably when applied across soil boundaries, resulting in absolute percentage errors of 〉1000 percent for low LAI. Minimization methods applied to merit functions constructed from differences between measured reflectances and predicted reflectances using multiple-scattering models are unacceptably sensitive to a good initial guess for the desired parameter. In contrast, the neural network reported generally yields absolute percentage errors of 〈30 percent when weighting coefficients trained on one soil type were applied to predicted canopy reflectance at a different soil background.
    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. 757-759.
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    Inferring total canopy APAR from PAR bidirectional reflectances and vegetation indices in tallgrass prairie (1992)
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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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    The NASA/JPL three-frequency polarimetric AIRSAR system (1992)
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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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    Monitoring of environmental conditions in the Alaskan forests using ERS-1 SAR data (1992)
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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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    An investigation of the relationship between tree water potential and dielectric constant (1992)
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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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    Radiometric correction of SAR images of varying terrain heights (1992)
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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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    Ground support for Space Shuttle earth observations by the NASA environment remote sensing analysis facility (ERSAF) (1992)
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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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    Relative phase calibration of the NASA/DC-8 three-frequency polarimetric SAR system (1992)
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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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    ESTAR - A synthetic aperture microwave radiometer for measuring soil moisture (1992)
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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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    Topographic mapping from ERS-1 and SEASAT radar interferometry (1992)
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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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  • 58
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    High-precision VLBI astrometry of the radio-emitting star Sigma CrB - A step in linking the Hipparcos and extragalactic reference frames (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: VLBI observations of the optically bright radio-emitting star Sigma Coronae Borealis (Sigma CrB) have yielded its position relative to an angularly nearby quasar, its annual proper motion and its trigonometric parallax with formal uncertainties slightly better than 0.2 milliarcsec. This is the first result of the VLBI astrometric program we are conducting on 11 radio stars similar to Sigma CrB. We plan to obtain comparable results for all stars when enough epochs of observations are acquired. These stars will be used to astrometrically link the Hipparcos and VLBI extragalactic reference frames.
    Schlagwort(e): ASTRONOMY
    Materialart: Astronomy and Astrophysics (ISSN 0004-6361); 258; 1; p. 112-115.
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    SALSA - A lunar submillimeter-wavelength array (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A conceptual design for a Synthesis Array for Lunar Submillimeter Astronomy (SALSA) is described with emphasis on information relevant to its implementation. SALSA is optimized to synthesize images of astronomical sources at wavelengths between 60 and 300 microns with an angular resolution of 10 milliarcseconds at the shortest wavelength. The discussion covers engineering considerations and descriptions of subsystems, including the environmental shield, antenna, and beam transport.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Engineering, construction, and operations in space - III: Space '92; Proceedings of the 3rd International Conference, Denver, CO, May 31-June 4, 1992. Vol. 2 (A93-41976 17-12); p. 1902-1912.
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  • 60
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    Mitigation of adverse environmental effects on lunar-based astronomical instruments (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The galactic cosmic-ray flux incident on the moon was examined for its potential adverse impact on the performance of the large lunar telescope (LLT) proposed as a part of NASA's Space Exploration Initiative (SEI). Noise produced by the cosmic-ray flux in the charge coupled devices to be used as the primary photodetector in the telescope was estimated. It was calculated that approximately 2.5 m of regolith would provide the shielding necessary to reduce the noise to an acceptable level. Dust is an omnipresent environmental concern for any human-assisted or robotic scientific instruments deployed on the moon. The degree to which dust poses an operational risk to the telescope was examined. Three potential methods for reducing this risk were identified: locating scientific instruments at remote locations; utilizing a prepared, dust-free site for all rocket activities; and covering the optics during high-risk times.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Engineering, construction, and operations in space III: Space '92; Proceedings of the 3rd International Conference, Denver, CO, May 31-June 4, 1992. Vol. 2 (A93-41976 17-12); p. 1832-1841.
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    The proposed NASA lunar-based astronomical observatories (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Plans for constructing permanent lunar bases and observatories under the Space Exploration Initiative are examined. The advantages of the lunar environment for astronomical observations are briefly reviewed, and the proposed lunar facilities are discussed. In particular, attention is given to a lunar optical interferometer, a submillimeter interferometer, a VLF radio array on the lunar far side, a large optical telescope, and a large installation for detecting gravitational waves. Each of the proposed instruments and their capabilities and configurations are discussed, as are possible experiments that may reduce the uncertainty and risk involved in setting up these facilities.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Engineering, construction, and operations in space III: Space '92; Proceedings of the 3rd International Conference, Denver, CO, May 31-June 4, 1992. Vol. 2 (A93-41976 17-12); p. 1798-1808.
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    Multispectral thermal infrared mapping of the 1 October 1988 Kupaianaha flow field, Kilauea volcano, Hawaii (1992)
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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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    Robust recognition of handwritten numerals based on dual cooperative network (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: An approach to robust recognition of handwritten numerals using two operating parallel networks is presented. The first network uses inputs in Cartesian coordinates, and the second network uses the same inputs transformed into polar coordinates. How the proposed approach realizes the robustness to local and global variations of input numerals by handling inputs both in Cartesian coordinates and in its transformed Polar coordinates is described. The required network structures and its learning scheme are discussed. Experimental results show that by tracking only a small number of distinctive features for each teaching numeral in each coordinate, the proposed system can provide robust recognition of handwritten numerals.
    Schlagwort(e): CYBERNETICS
    Materialart: In: IJCNN - International Joint Conference on Neural Networks, Baltimore, MD, June 7-11, 1992, Proceedings. Vol. 3 (A93-37001 14-63); p. III-760 to III-76
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    Multi-use lunar telescopes (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The objective of multi-use telescopes is to reduce the initial and operational costs of space telescopes to the point where a fair number of telescopes, a dozen or so, would be affordable. The basic approach is to develop a common telescope, control system, and power and communications subsystem that can be used with a wide variety of instrument payloads, i.e., imaging CCD cameras, photometers, spectrographs, etc. By having such a multi-use and multi-user telescope, a common practice for earth-based telescopes, development cost can be shared across many telescopes, and the telescopes can be produced in economical batches.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Robotic telescopes in the 1990s; Proceedings of the Symposium, 103rd Annual Meeting of the Astronomical Society of the Pacific, Univ. of Wyoming, Laramie, June 22-24, 1991, 1991 (A93-36457 14-89); p. 289-303.
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    The use of robotic telescopes for detecting planetary systems (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: It is argued that increases in the precision of photometric measurements and the development of fully automatic photometric telescopes (APTs) now make possible the detection of Jupiter-size objects around other stars. The two most promising approaches are to monitor binary stars that have their orbital plane nearly in our line of sight and to measure the rotation periods of stars that are known to have dark companions and have very accurate values for Vsini. Differential photometry with APTs, based on a rapid comparison among a group of stars, provides a precision of 2 parts in 1000. Transits of solar-type stars by planets or brown dwarfs the size of Jupiter or Saturn will produce brightness variations of about 10 parts per 1000.
    Schlagwort(e): ASTRONOMY
    Materialart: In: Robotic telescopes in the 1990s; Proceedings of the Symposium, 103rd Annual Meeting of the Astronomical Society of the Pacific, Univ. of Wyoming, Laramie, June 22-24, 1991, 1991 (A93-36457 14-89); p. 153-169.
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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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    Earth observations during Space Shuttle mission STS-45 Mission to Planet Earth - March 24-April 2, 1992 (1992)
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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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    Developments of new force reflecting control schemes and an application to a teleoperation training simulator (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: Two schemes of force reflecting control, position-error based force reflection and low-pass-filtered force reflection, both combined with shared compliance control, were developed for dissimilar master-slave arms. These schemes enabled high force reflection gains, which were not possible with a conventional scheme when the slave arm was much stiffer than the master arm. The experimental results with a peg-in-hole task indicated that the newly force reflecting control schemes combined with compliance control resulted in best task performances. As a related application, a simulated force reflection/shared compliance control teleoperation trainer was developed that provided the operator with the feel of kinesthetic force virtual reality.
    Schlagwort(e): CYBERNETICS
    Materialart: In: 1992 IEEE International Conference on Robotics and Automation, 8th, Nice, France, May 12-14, 1992, Proceedings. Vol. 2 (A93-35501 13-63); p. 1412-1419.
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    Man-equivalent telepresence through four fingered human-like hand system (1992)
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    Beschreibung: The author describes a newly developed mechanical hand system. The robot hand is in human-like configuration with a thumb and three fingers, a palm, a wrist, and the forearm in which the hand and wrist actuators are located. Each finger and the wrist has its own active electromechanical compliance system, allowing the joint drive trains to be stiffened or loosened. This mechanism imitates the human muscle dual function of positioner and stiffness controller. This is essential for soft grappling operations. The hand-wrist assembly has 16 finger joints, three wrist joints, and five compliance mechanisms for a total of 24 degrees of freedom. The strength of the hand is roughly half that of the human hand and its size is comparable to a male hand. The hand is controlled through an exoskeleton glove controller that the operator wears. The glove provides the man-machine interface in telemanipulation control mode: it senses the operator's inputs to guide the mechanical hand in hybrid position and force control. The hand system is intended for dexterous manipulations in structured environments. Typical applications will include work in hostile environment such as space operations and nuclear power plants.
    Schlagwort(e): CYBERNETICS
    Materialart: In: 1992 IEEE International Conference on Robotics and Automation, 8th, Nice, France, May 12-14, 1992, Proceedings. Vol. 1 (A93-35501 13-63); p. 843-848.
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    An advanced teleoperator control system - Design and evaluation (1992)
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    Beschreibung: The design goal of an advanced teleoperator control system is twofold: 1) to allow the operator's manual control to be robust to system nonlinearities such as time delays and operator's control errors, and 2) to support the high performance of teleoperation while reducing the operator's control burden by providing the master and slave arms with desirable dynamic properties and by allowing the slave arm to automatically perform such control tasks as compliance and force control in the form of task sharing. The authors present a novel teleoperator control system achieving the above design goal by taking the following into consideration: the human dynamics involved in generating control command based on visual and forced feedback is modeled and incorporated into the controller design and evaluation; the dynamic characteristics of slave and master arms are actively modified in such a way as to implement the desirable dynamic characteristics; and the force feedback is redefined in terms of the combination of opposition and force discrepancies in order to establish the required man/machine dynamic coordination under shared control. The proposed control system with human dynamics in the control loop is simulated and compared with a number of conventional methods in the presence of human control errors and time delays.
    Schlagwort(e): CYBERNETICS
    Materialart: In: 1992 IEEE International Conference on Robotics and Automation, 8th, Nice, France, May 12-14, 1992, Proceedings. Vol. 1 (A93-35501 13-63); p. 859-864.
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    On pose determination using point features (1992)
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    Beschreibung: Consideration is given to the vision subsystem of an Orbital Replacement Unit (ORU) that was placed onto its base at Goddard Space Flight Center by a PUMA 762 robot equipped with a wrist-mounted CCD camera and a wrist-mounted force sensor. It is found that a simple adaptive thresholding method works quite well for images taken under various lighting conditions. The pose computed using the quadrangle method is reasonable for real images. In the presence of image feature noise the accuracy of the computed pose can be considerably reduced. This problem can be solved by using a 3D marker and an alternative pose computation algorithm.
    Schlagwort(e): CYBERNETICS
    Materialart: In: Cooperative intelligent robotics in space II; Proceedings of the Meeting, Boston, MA, Nov. 12-14, 1991 (A93-27001 09-54); p. 210-221.
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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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    Gamma ray observations of the Crab pulsar - Past, present, future (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The paper describes some of the high-energy observations of the Crab-Nebula pulsar, PSR0531+22. The pulse profiles of the Crab pulsar obtained in balloon-borne observations in 1967 and 1980 are presented. At present, gamma-ray scintillation detectors aboard the Gamma Ray Observatory (GRO) form the basis of the Burst and Transient Source Experiment (BATSE). The pulsar, which is observed daily by the BATSE, is used by all four GRO/BATSE detectors as a calibration source since it emits a steady, strong, well-known spectrum of gamma rays over the entire energy range to which detectors are sensitive. The paper presents an example of a pulse profile obtained with the BATSE.
    Schlagwort(e): ASTRONOMY
    Materialart: New York Academy of Sciences, Annals (ISSN 0077-8923); p. 309-318.
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    Continuous motion using task-directed stereo vision (1992)
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    Beschreibung: The performance of autonomous mobile robots performing complex navigation tasks can be dramatically improved by directing expensive sensing and planning in service of the task. The task-direction algorithms can be quite simple. In this paper we describe a simple task-directed vision system which has been implemented on a real outdoor robot which navigates using stereo vision. While the performance of this particular robot was improved by task-directed vision, the performance of task-directed vision in general is influenced in complex ways by many factors. We briefly discuss some of these, and present some initial simulated results.
    Schlagwort(e): CYBERNETICS
    Materialart: In: Sensor fusion IV: Control paradigms and data structures; Proceedings of the Meeting, Boston, MA, Nov. 12-15, 1991 (A93-49438 21-63); p. 294-298.
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    Manifold traversing as a model for learning control of autonomous robots (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: This paper describes a recipe for the construction of control systems that support complex machines such as multi-limbed/multi-fingered robots. The robot has to execute a task under varying environmental conditions and it has to react reasonably when previously unknown conditions are encountered. Its behavior should be learned and/or trained as opposed to being programmed. The paper describes one possible method for organizing the data that the robot has learned by various means. This framework can accept useful operator input even if it does not fully specify what to do, and can combine knowledge from autonomous, operator assisted and programmed experiences.
    Schlagwort(e): CYBERNETICS
    Materialart: In: Sensor fusion IV: Control paradigms and data structures; Proceedings of the Meeting, Boston, MA, Nov. 12-15, 1991 (A93-49438 21-63); p. 77-87.
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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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    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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    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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    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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    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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    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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    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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    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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    Learning a trajectory using adjoint functions and teacher forcing (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A new methodology for faster supervised temporal learning in nonlinear neural networks is presented which builds upon the concept of adjoint operators to allow fast computation of the gradients of an error functional with respect to all parameters of the neural architecture, and exploits the concept of teacher forcing to incorporate information on the desired output into the activation dynamics. The importance of the initial or final time conditions for the adjoint equations is discussed. A new algorithm is presented in which the adjoint equations are solved simultaneously (i.e., forward in time) with the activation dynamics of the neural network. We also indicate how teacher forcing can be modulated in time as learning proceeds. The results obtained show that the learning time is reduced by one to two orders of magnitude with respect to previously published results, while trajectory tracking is significantly improved. The proposed methodology makes hardware implementation of temporal learning attractive for real-time applications.
    Schlagwort(e): CYBERNETICS
    Materialart: Neural Networks (ISSN 0893-6080); p. 473-484.
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    A new neural net approach to robot 3D perception and visuo-motor coordination (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A novel neural network approach to robot hand-eye coordination is presented. The approach provides a true sense of visual error servoing, redundant arm configuration control for collision avoidance, and invariant visuo-motor learning under gazing control. A 3-D perception network is introduced to represent the robot internal 3-D metric space in which visual error servoing and arm configuration control are performed. The arm kinematic network performs the bidirectional association between 3-D space arm configurations and joint angles, and enforces the legitimate arm configurations. The arm kinematic net is structured by a radial-based competitive and cooperative network with hierarchical self-organizing learning. The main goal of the present work is to demonstrate that the neural net representation of the robot 3-D perception net serves as an important intermediate functional block connecting robot eyes and arms.
    Schlagwort(e): CYBERNETICS
    Materialart: In: IJCNN - International Joint Conference on Neural Networks, Baltimore, MD, June 7-11, 1992, Proceedings. Vol. 1 (A93-37001 14-63); p. I-299 to I-307.
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    Extrapolation limitations of multilayer feedforward neural networks (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: The limitations of backpropagation used as a function extrapolator were investigated. Four common functions were used to investigate the network's extrapolation capability. The purpose of the experiment was to determine whether neural networks are capable of extrapolation and, if so, to determine the range for which networks can extrapolate. The authors show that neural networks cannot extrapolate and offer an explanation to support this result.
    Schlagwort(e): CYBERNETICS
    Materialart: In: IJCNN - International Joint Conference on Neural Networks, Baltimore, MD, June 7-11, 1992, Proceedings. Vol. 4 (A93-37001 14-63); p. IV-25 to IV-30.
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    Fast neural solution of a nonlinear wave equation (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: A neural algorithm for rapidly simulating a certain class of nonlinear wave phenomena using analog VLSI neural hardware is presented and applied to the Korteweg-de Vries partial differential equation. The corresponding neural architecture is obtained from a pseudospectral representation of the spatial dependence, along with a leap-frog scheme for the temporal evolution. Numerical simulations demonstrated the robustness of the proposed approach.
    Schlagwort(e): CYBERNETICS
    Materialart: In: IJCNN - International Joint Conference on Neural Networks, Baltimore, MD, June 7-11, 1992, Proceedings. Vol. 3 (A93-37001 14-63); p. III-10 to III-15.
    Format: text
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    An algorithm for the estimation of water temperatures from thermal multispectral airborne remotely sensed data (1992)
    In:  Other Sources
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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.
    Format: text
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    Automated digital motion-video abstraction - A fuzzy measure approach (1992)
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    Publikationsdatum: 2011-08-24
    Beschreibung: This paper addresses a solution to the problem of scene estimation of motion video data in the fuzzy set theoretic framework. Using fuzzy image feature extractors, a new algorithm is developed to compute the change of information in each of two successive frames to classify scenes. This classification process of raw input visual data can be used to establish structure for correlation. The algorithm attempts to fulfill the need for non-linear, frame-accurate access to video data for applications such as video editing and visual document archival/retrieval systems in multimedia environments.
    Schlagwort(e): CYBERNETICS
    Materialart: In: Intelligent robots and computer vision XI: Biological, neural net, and 3-D methods; Proceedings of the Meeting, Boston, MA, Nov. 18-20, 1992 (A93-33171 12-63); p. 342-353.
    Format: text
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