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At least 937 records · Page 52
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Spaceborne radar observations: A guide for Magellan radar-image analysis

Geologic analyses of spaceborne radar images of Earth are reviewed and summarized with respect to detecting, mapping, and interpreting impact craters, volcanic landforms, eolian and subsurface features, and tectonic landforms. Interpretations are illustrated mostly with Seasat synthetic aperture radar and shuttle-imaging-radar images. Analogies are drawn for the potential interpretation of radar images of Venus, with emphasis on the effects of variation in Magellan look angle with Venusian latitude. In each landform category, differences in feature perception and interpretive capability are related to variations in imaging geometry, spatial resolution, and wavelength of the imaging radar systems. Impact craters and other radially symmetrical features may show apparent bilateral symmetry parallel to the illumination vector at low look angles. The styles of eruption and the emplacement of major and minor volcanic constructs can be interpreted from morphological features observed in images. Radar responses that are governed by small-scale surface roughness may serve to distinguish flow types, but do not provide unambiguous information. Imaging of sand dunes is rigorously constrained by specific angular relations between the illumination vector and the orientation and angle of repose of the dune faces, but is independent of radar wavelength. With a single look angle, conditions that enable shallow subsurface imaging to occur do not provide the information necessary to determine whether the radar has recorded surface or subsurface features. The topographic linearity of many tectonic landforms is enhanced on images at regional and local scales, but the detection of structural detail is a strong function of illumination direction. Nontopographic tectonic lineaments may appear in response to contrasts in small-surface roughness or dielectric constant. The breakpoint for rough surfaces will vary by about 25 percent through the Magellan viewing geometries from low to high Venusian latitudes. Examples of anomalies and system artifacts that can affect image interpretation are described.

Ford, J. P.↗
NASA NTRS1991

Improved disparity map analysis through the fusion of monocular image segmentations

The focus is to examine how estimates of three dimensional scene structure, as encoded in a scene disparity map, can be improved by the analysis of the original monocular imagery. The utilization of surface illumination information is provided by the segmentation of the monocular image into fine surface patches of nearly homogeneous intensity to remove mismatches generated during stereo matching. These patches are used to guide a statistical analysis of the disparity map based on the assumption that such patches correspond closely with physical surfaces in the scene. Such a technique is quite independent of whether the initial disparity map was generated by automated area-based or feature-based stereo matching. Stereo analysis results are presented on a complex urban scene containing various man-made and natural features. This scene contains a variety of problems including low building height with respect to the stereo baseline, buildings and roads in complex terrain, and highly textured buildings and terrain. The improvements are demonstrated due to monocular fusion with a set of different region-based image segmentations. The generality of this approach to stereo analysis and its utility in the development of general three dimensional scene interpretation systems are also discussed.

Perlant, Frederic P.↗
NASA NTRS1991

The behavior of wave 2 in the Southern Hemisphere stratosphere during late winter and early spring

The behavior of wave 2 in the Southern Hemisphere (SH) winter and early spring stratosphere has been examined in detail using 10 years of NMC data. Wave 2 is characterized by a broad meridional structure peaking between 55 and 65 S, and regular eastward propagation, with periods ranging from 5 to 40 days. The range of maximum geopotential height amplitudes is from 600 to 1000 m for a year. Consideration is also given to the relationship of wave 2 to other features of stratospheric circulation, Eliassen-Palm fluxes, and synoptic maps. The results obtained show that the zonal mean state of the SH stratosphere frequently satisfies conditions for instability. It is concluded that both instability of zonally symmetric and asymmetric states, and nonlinear interactions between wave 1 and wave 2 are of importance for determining the behavior of wave 2 in the SH winter and spring stratosphere.

Manney, G. L.↗
NASA NTRS1991

Synoptic maps for the heliospheric Thomson scattering brightness as observed by the Helios photometers

A method for displaying the electron Thomson scattering intensity in the inner heliosphere as observed by the zodiacal light photometers on board the Helios spacecraft in the form of synoptic maps is presented. The method is based on the assumption that the bulk of the scattering electrons along the line of sight is located near the point closest to the sun. Inner-heliospheric structures will generally be represented properly in these synoptic maps only if they are sufficiently long-lived (that is, a significant fraction of a solar rotation period). The examples of Helios synoptic maps discussed (from data in April 1976 and November 1978), indicate that it is possible to identify large-scale, long-lived density enhancements in the inner heliosphere. It is expected that the Helios synoptic maps will be particularly useful in the study of corotating structures (e.g., streamers), and the maps will be most reliable during periods when few transient featurs are present in the corona, i.e., during solar minimum.

Hick, P.↗
NASA NTRS1991

Magellan - Mission summary

The surface morphology, electrical properties, and related processes of Venus are the major areas of investigation of the Magellan Mission. The spacecraft employs a SAR for imaging, altimetry, and radiometry, and the mapping of 83 percent of the surface was complete after one of Venus' sidereal days. The strips of image data can provide a global map of Venus to permit the determination of such geologic features as volcanic and tectonic patterns.

Saunders, R. S.↗
NASA NTRS1992

Electron spectroscopy analysis

The Surface Science Laboratories at the University of Alabama in Huntsville (UAH) are equipped with x-ray photoelectron spectroscopy (XPS or ESCA) and Auger electron spectroscopy (AES) facilities. These techniques provide information from the uppermost atomic layers of a sample, and are thus truly surface sensitive. XPS provides both elemental and chemical state information without restriction on the type of material that can be analyzed. The sample is placed into an ultra high vacuum (UHV) chamber and irradiated with x-rays which cause the ejection of photoelectrons from the sample surface. Since x-rays do not normally cause charging problems or beam damage, XPS is applicable to a wide range of samples including metals, polymers, catalysts, and fibers. AES uses a beam of high energy electrons as a surface probe. Following electronic rearrangements within excited atoms by this probe, Auger electrons characteristic of each element present are emitted from the sample. The main advantage of electron induced AES is that the electron beam can be focused down to a small diameter and localized analysis can be carried out. On the rastering of this beam synchronously with a video display using established scanning electron microscopy techniques, physical images and chemical distribution maps of the surface can be produced. Thus very small features, such as electronic circuit elements or corrosion pits in metals, can be investigated. Facilities are available on both XPS and AES instruments for depth-profiling of materials, using a beam of argon ions to sputter away consecutive layers of material to reveal sub-surface (and even semi-bulk) analyses.

Gregory, John C.↗
NASA NTRS1994

Noachian and Hesperian modification of the original Chryse impact basin topography

We propose a new center (35.5 W, 32.5 N) and ring assignment for the original Chryse impact basin based on photogeologic mapping and re-examination of the published geology. Noachian features in the Chryse Planitia area are the best indicators of the original ancient multiringed impact structure. While other workers have centered the Chryse impact on the topographic low associated with Hesperian volcanic and fluvial deposits, we suggest that the center of the original Noachian-age excavation cavity was located 800 km farther NE, and the basin topography was significantly modified over time.

Stockman, Stephanie↗
NASA NTRS1994

Evidence, age, and thickness of a frozen Paleolake in Utopia Planitia, Mars

Recent mapping studies west of Elysium Mons, Mars, have pinpointed subice features that suggest the existence of a frozen paleolake in Utopia Planitia as recently as 1.8 billion years ago. The subice features are interpreted to be hyaloclastic ridges and hills, table moutains, associated joekulhalaup deposits, and fluvial channels. Photoclinometric studies of these features and of a basal scarp around the northwest flank of Elysium Mons interpreted to have been an ice-sheet boundary indicate that the maximum thickness of ice within the basin may have been about 180 m. This thickness of ice during a relatively late stage of Martian geologic history would have important implications concerning the atmospheric, the climatic, and possibly the exobiologic history of the planet.

Chapman, Mary G.↗
NASA NTRS1995

The Geology of Callisto

The geology of Callisto is not boring. Although cratered terrain dominates Callisto (a key end-member of the Jovian satellite system), a number of more interesting features are apparent. Cratered terrain is broken into irregular map-able bright and dark subunits that vary in albedo by a factor of 2, and several relatively smooth units are depleted of small craters. Some of these areas may have been volcanically resurfaced. Lineaments, including parallel and radial sets, may be evidence for early global tectonism. Frost deposition occurs in cold traps, and impact scars have formed from tidally disrupted comets. Geologic evidence suggests that Callisto does have a chemically differentiated crust. Central pit and central dome craters and palimpsests are common. The preferred interpretation is that a relatively ice-rich material, at depths of 5 km or more, has been mobilized during impact and exposed as domes or palimpsests. The close similarity in crater morphologies and dimensions indicates that the outermost 10 km or so of Callisto may be as differentiated as on Ganymede. The geology of cratered terrain on Callisto is simpler than that of cratered terrain on Ganymede, however. Orbital evolution and tidal heating may provide the answer to the riddle of why Callisto and Ganymede are so different (Malhotra, 1991). We should expect a few surprises and begins to answer some fundamental questions when Callisto is observed by Galileo in late 1996.

Schenk, Paul M.↗
NASA NTRS2000

BOREAS AFM-12 1-km AVHRR Seasonal Land Cover Classification

The Boreal Ecosystem-Atmosphere Study (BOREAS) Airborne Fluxes and Meteorology (AFM)-12 team's efforts focused on regional scale Surface Vegetation and Atmosphere (SVAT) modeling to improve parameterization of the heterogeneous BOREAS landscape for use in larger scale Global Circulation Models (GCMs). This regional land cover data set was developed as part of a multitemporal one-kilometer Advanced Very High Resolution Radiometer (AVHRR) land cover analysis approach that was used as the basis for regional land cover mapping, fire disturbance-regeneration, and multiresolution land cover scaling studies in the boreal forest ecosystem of central Canada. This land cover classification was derived by using regional field observations from ground and low-level aircraft transits to analyze spectral-temporal clusters that were derived from an unsupervised cluster analysis of monthly Normalized Difference Vegetation Index (NDVI) image composites (April-September 1992). This regional data set was developed for use by BOREAS investigators, especially those involved in simulation modeling, remote sensing algorithm development, and aircraft flux studies. Based on regional field data verification, this multitemporal one-kilometer AVHRR land cover mapping approach was effective in characterizing the biome-level land cover structure, embedded spatially heterogeneous landscape patterns, and other types of key land cover information of interest to BOREAS modelers.The land cover mosaics in this classification include: (1) wet conifer mosaic (low, medium, and high tree stand density), (2) mixed coniferous-deciduous forest (80% coniferous, codominant, and 80% deciduous), (3) recent visible bum, vegetation regeneration, or rock outcrops-bare ground-sparsely vegetated slow regeneration bum (four classes), (4) open water and grassland marshes, and (5) general agricultural land use/ grasslands (three classes). This land cover mapping approach did not detect small subpixel-scale landscape features such as fens, bogs, and small water bodies. Field observations and comparisons with Landsat Thematic Mapper (TM) suggest a minimum effective resolution of these land cover classes in the range of three to four kilometers, in part, because of the daily to monthly compositing process. In general, potential accuracy limitations are mitigated by the use of conservative parameterization rules such as aggregation of predominant land cover classes within minimum horizontal grid cell sizes of ten kilometers. The AFM-12 one-kilometer AVHRR seasonal land cover classification data are available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). The data files are available on a CD-ROM (see document number 20010000884).

Steyaert, Lou↗
NASA NTRS2019

Feature Learning for Multispectral Satellite Imagery Classification Using Neural Architecture Search

Automated classification of remote sensing data is an integral tool for earth scientists, and deep learning has proven very successful at solving such problems. However, building deep learning models to process the data requires expert knowledge of machine learning. We introduce DELTA, a software toolkit to bridge this technical gap and make deep learning easily accessible to earth scientists. Visual feature engineering is a critical part of the machine learning lifecycle, and hence is a key area that will be automated by DELTA. Hand-engineered features can perform well, but require a cross functional team with expertise in both machine learning and the specific problem domain, which is costly in both researcher time and labor. The problem is more acute with multispectral satellite imagery, which requires considerable computational resources to process. In order to automate the feature learning process, a neural architecture search samples the space of asymmetric and symmetric autoencoders using evolutionary algorithms. Since denoising autoencoders have been shown to perform well for feature learning, the autoencoders are trained on various levels of noise and the features generated by the best performing autoencoders evaluated according to their performance on image classification tasks. The resulting features are demonstrated to be effective for Landsat-8 flood mapping, as well as benchmark datasets CIFAR10 and SVHN.

Robert Campbell↗
NASA NTRS2024

Subsurface Thermophysical Properties of Europa's Leading and Trailing Hemispheres as Revealed by ALMA

We present best-fit values of porosity—and the corresponding effective thermal inertiae—determined from three different depths in Europa's near-subsurface (∼1–20 cm). The porosity of the upper ∼20 cm of Europa's subsurface varies between 75% and 50% (Γeff ≈ 50–140 J m −2 K −1 s −1/2 ) on the leading hemisphere and 50%–40% (Γeff ≈ 140–180 J m −2 K −1 s −1/2 ) on the trailing hemisphere. Residual maps produced by comparison with these models reveal thermally anomalous features that cannot be reproduced by globally homogeneous porosity models. These regions are compared to Europa's surface terrain and known compositional variations. We find that some instances of warm thermal anomalies are co-located with known geographical or compositional features on both the leading and trailing hemisphere; cool temperature anomalies are well correlated with surfaces previously observed to contain pure, crystalline water ice and the expansive rays of Pwyll crater. Anomalous regions correspond to locations with subsurface properties different from those of our best-fit models, such as potentially elevated thermal inertia, decreased emissivity, or more porous regolith. We also find that ALMA observations at ∼3 mm sound below the thermal skin depth of Europa (∼10–15 cm) for a range of porosity values, and thus do not exhibit features indicative of diurnal variability or residuals similar to other frequency bands. Future observations of Europa at higher angular resolution may reveal additional locations of variable subsurface thermophysical properties, while those at other wavelengths will inform our understanding of the regolith compaction length and the effects of external processes on the shallow subsurface.

Alexander E Thelen↗
NASA NTRS2023

Cosmological Shocks Around Galaxy Clusters: A Coherent Investigation With DES, SPT & ACT

We search for signatures of cosmological shocks in gas pressure profiles of galaxy clusters using the cluster catalogues from three surveys: the Dark Energy Survey (DES) Year 3, the South Pole Telescope (SPT) SZ survey, and the Atacama Cosmology Telescope (ACT) data releases 4, 5, and 6, and using thermal Sunyaev–Zeldovich (SZ) maps from SPT and ACT. The combined cluster sample contains around 105 clusters with mass and redshift ranges 10 13.7 200m /M ⊙ <10 15.5 and 0.1 < z < 2, and the total sky coverage of the maps is ≈15000deg 2 ⁠. We find a clear pressure deficit at R/R 200m ≈ 1.1 in SZ profiles around both ACT and SPT clusters, estimated at 6σ significance, which is qualitatively consistent with a shock-induced thermal non-equilibrium between electrons and ions. The feature is not as clearly determined in profiles around DES clusters. We verify that measurements using SPT or ACT maps are consistent across all scales, including in the deficit feature. The SZ profiles of optically selected and SZ-selected clusters are also consistent for higher mass clusters. Those of less massive, optically selected clusters are suppressed on small scales by factors of 2–5 compared to predictions, and we discuss possible interpretations of this behaviour. An oriented stacking of clusters – where the orientation is inferred from the SZ image, the brightest cluster galaxy, or the surrounding large-scale structure measured using galaxy catalogues – shows the normalization of the one-halo and two-halo terms vary with orientation. Finally, the location of the pressure deficit feature is statistically consistent with existing estimates of the splashback radius.

galaxies↗
DOE OSTI2025

Wide‐Field Bond Quality Evaluation Using Frequency Domain Thermoreflectance with Deep Neural Network Feature Reconstruction

Heterogeneous integration of microelectronic components provides a pathway to improve circuit/component performance; however, this comes with assembly challenges, in particular due to complex interfaces via subsurface bump bonds. The ability of these bonds to transmit electrical signals and conduct heat to the carrier substrate limits component performance. In this work, hyperspectral frequency‐domain thermoreflectance (FDTR) imaging is demonstrated as a robust technique for evaluating the quality of subsurface indium bump bonds in a surrogate microelectronic sample. By performing microscale FDTR imaging with coarse motion image stitching, thermal phase maps that cover a 4 mm by 4 mm field‐of‐view with subsurface feature sensitivity at depths greater than 50 µm are obtained. The resulting FDTR hyperspectral data contains more than three million pixels and reveal the quality of subsurface microbump arrays. Wide‐field analysis of bonded versus gap regions is enabled by deep neural network feature reconstruction, that after training, rapidly provides an interpretable representation of bond quality. Utility of noisy higher frequency FDTR phase maps, i.e., near the computationally predicted sensing depth limit, results in an average prediction error of 11%. Taken together, FDTR with neural network‐based analysis demonstrates subsurface bond monitoring at length scales relevant for heterogeneously integrated microelectronics.

FDTR↗
NASA NTRS1974

Selected satellite data on snow and ice in the Great Lakes basin 1972-73 /IFYGL/

Three snow-extent maps of the Lake Ontario drainage basin were prepared from NOAA-2 satellite visible band images during the International Field Year for the Great Lakes. These maps are discussed and the satellite data are evaluated for snow-extent mapping. The value of ERTS-1 imagery and digital data is also discussed in relation to the Lake Ontario basin studies. ERTS-1 MSS data are excellent for ice identification and analysis but are not useful for forecasting where timely receipt of data is imperative. NOAA-2 VHRR data are timely but the lower resolution of the VHRR makes identification of certain ice features difficult. NOAA-2 VHRR is well suited for snow-extent maps and thermal maps of large areas such as the 19,000 sq-km Lake Ontario basin.

Wiesnet, D. R.↗
NASA NTRS1973

Monitoring the vernal advancement and retrogradation (green wave effect) of natural vegetation

The author has identified the following significant results. Preliminary evaluation of autumnal phase ground truth data suggests that the sampling procedures at the Great Plains Corridor network test sites are adequate to show relatively small temporal changes in above-ground vegetation biomass and vegetation condition. Vegetation changes measured August through December, reflect grazing intensity and environmental conditions at the test sites. Preliminary analysis of black and white imagery suggests that detail in vegetation patterns is much greater than originally anticipated. A first look analysis of single band imagery and digital data at two locations shows that woodland, grassland, and cropland areas are easily delineated. Computer derived grey-scale maps from MSS digital data were shown to be useful in identifying the location of small fields and features of the natural and cultivated lands. Single band imagery and digital data are believed to have important application for synoptic land use mapping and inventory. Initial ratio analysis, using band 5 and 7 data, suggests the applicability in the greenness of a vegetative scene.

Rouse, J. W., Jr.↗
NASA NTRS2000

BOREAS Hardcopy Maps

Boreal Ecosystem-Atmospheric Study (BOREAS) hardcopy maps are a collection of approximately 1,000 hardcopy maps representing the physical, climatological, and historical attributes of areas covering primarily the Manitoba and Saskatchewan provinces of Canada. These maps were collected by BOREAS Information System (BORIS) and Canada for Remote Sensing (CCRS) staff to provide basic information about site positions, manmade features, topography, geology, hydrology, land cover types, fire history, climate, and soils of the BOREAS study region. These maps are not available for distribution through the BOREAS project but may be used as an on-site resource. Information is provided within this document for individuals who want to order copies of these maps from the original map source. Note that the maps are not contained on the BOREAS CD-ROM set. An inventory listing file is supplied on the CD-ROM to inform users of the maps that are available. This inventory listing is available from the Earth Observing System Data and Information System (EOSDIS) Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC). For hardcopies of the individual maps, contact the sources provided.

Hall, Forrest G.↗