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At least 199 records · Page 11

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NASA NTRS1986

Soil types and forest canopy structures in southern Missouri: A first look with AIS data

Spectral reflectance properties of deciduous oak-hickory forests covering the eastern half of the Rolla Quadrangle were examined using Thematic Mapper (TM) data acquired in August and December, 1982 and Airborne Imaging Spectrometer (AIS) data acquired in August, 1985. For the TM data distinctly high relative reflectance values (greater than 0.3) in the near infrared (Band 4, 0.73 to 0.94 micrometers) correspond to regions characterized by xeric (dry) forests that overlie soils with low water retention capacities. These soils are derived primarily from rhyolites. More mesic forests characterized by lower TM band 4 relative reflectances are associated with soils of higher retention capacities derived predominately from non-cherty carbonates. The major factors affecting canopy reflectance appear to be the leaf area index (LAI) and leaf optical properties. The Suits canopy reflectance model predicts the relative reflectance values for the xeric canopies. The mesic canopy reflectance is less well matched and incorporation of canopy shadowing caused by the irregular nature of the mesic canopy may be necessary. Preliminary examination of high spectral resolution AIS data acquired in August of 1985 reveals no more information than found in the broad band TM data.

Green, G. M.↗

NASA NTRS1987

Implications of Viking color data for evolution of the Amenthes Region, Mars

In the Eastern Hemisphere of Mars, where the hemispheric dichotomy is not overlain by relatively recent flows from the Tharsis volcanoes, the Mars cratered terrain boundary (CTB) now exists as highly fractured terrain juxtaposed with the smooth plains of the Northern Hemisphere. Based on Mariner 9 photography, the southern cratered terrain in the Amenthes region (0 to 30 deg N, 225 to 270 deg W) is approximately 3 to 4 km above the northern plains, and the transition zone is marked by both broad plateaus and knobby terrain. In the Amenthes Southest quadrangle, in particular, the continuum between large detached plateaus, smaller smooth topped plateaus and knobby hills can be seen. To define the previous position and evolution of the boundary, the distribution of cratered terrain, characteristic landforms (knobby terrain and detached plateaus) have been mapped, as well as structural features across the boundary. Structural mapping indicates that geological formations parallel the boundary in the Eastern Hemisphere with the conclusion that CTB evolution involved normal faulting through extension perpendicular to the boundary.

Maxwell, Ted A.↗

NASA NTRS1987

Tectonic domains in the Eastern Hemisphere of Mars

The definition of boundaries of discrete structural provinces on the surface of Mars has previously been made by the assumptions of circular or radial symmetry (in the case of the Tharsis olateau), by artificial quadrangle boundaries for regional studies, or simply by regional geographical features. Much of the planetary structural mapping has been presented in a line or spot format in existing consortium data. Methods are being generated to convert the detailed maps of tectonic features to a format that can be used with standard image processing techniques. In this manner such data can be more readily compared to age and other attributes deduced from geological mapping, gravity results, and topography. The 24 photomosaics covering the Eastern Hemisphere of Mars have already been examined for four types of structural features: erosional remnants, ridges, graben, and scarps. When digitized, each feature was flagged according to feature type, azimuth and length. These values were stored as text files on a quad-by-quad basis for each quad studied.

Maxwell, Ted A.↗

NASA NTRS1987

Progress in compilation of the 1:2,000,000-scale topographic map

The application of special photogrammetric techniques has enabled the systematic mapping of Mars' topography at a scale of 1:2,000,000, using high-altitude Viking Orbiter pictures. In fiscal 86, compilation was completed of the 24 subquadrangles that make up the quadrangles MC-12, MC-13, MC-14, MC-15, MC-20, and MC-21. This work completes compilation of the 60 topographic maps covering the equatorial belt (lat. + or - 30 deg). The remaining 80 subquadrangles of Mars are planned to be completed within 3 years (27, 27 and 26 subquadrangles, in fiscal 87, 88, and 89, respectively). Elevations on all topographic maps are relative to the Mars topographic datum. The maps have a contour interval of 1 km and a precision of + or - 1 km. The equatorial-belt maps are Mercator projections having true scale at lat. + or - 27.476 deg. These maps provide more precise information than do those previously available and they will help in understanding the geologic processes that have shaped the Martian surface.

Wu, Sherman S. C.↗

NASA NTRS1988

The surface integral approach to radarclinometry

A radar image of the Lake Champlain West quadrangle in the Adirondack Mountains of the U.S. is synthesized and used to test the surface integral approach to radarclinometry. It is shown that the surface integral approach to radarclinometry possesses an inherent instability that can be avoided only if the radar reflectance function possesses a shallow slope over the range of operation and if terrain slopes are bounded to prevent their being either parallel or perpendicular to the Poynting vector of the radar irradiance. It is found that the noise associated with real SAR systems makes this instability worse. It is concluded that the value of the surface integral approach to radarclinometry shows little promise.

Wildey, Robert L.↗

NASA NTRS1988

Possible breakup of dark terrain on Ganymede by large-scale shear faulting

The questions of relative motions of large segments of Ganymede's lithosphere and of the effect of any motions on grooved terrain formation are reexamined. Resolvable furrows in both hemispheres were mapped in great detail using Voyager 1 and 2 images and U.S. Geological Survey controlled shaded-relief quadrangle maps. Estimates of the Galileo Regio and Marius Regio poles of furrow concentricity indicate a considerable westward offset of the Galileo Regio pole, suggesting the possibility of about 500-km of left-lateral offset of the two areas. There is evidence that shear deformation was concentrated along a major structural lineament which follows a small circle and encloses Galileo Regio, and that a smaller amount of distributed shear occurred across an adjacent 500- to 1500-km-wide band. The results indicate that either widespread shear strain or the shear's driving mechanism may have had a long-term effect on patterns of deformation of Ganymede's lithosphere.

Murchie, Scott L.↗

NASA NTRS1988

Radarclinometry - Bootstrapping the radar reflectance function from the image pixel-signal frequency distribution and an altimetry profile

A method for determining the dependence of radar backscatter on incidence angle that is applicable to the region corresponding to a particular radar image is derived. The method is based on enforcing mathematical consistency between the frequency distribution of the images' pixel signals and a one-dimensional frequency distribution of slope component, which is obtained from a radar or laser altimetry profile in or near the imaged area. To test the resulting algorithm, an arbitrarily selected reflectance function is used to generate an artificial radar image from a digitized topographic map of the Lake Champlain West quadrangle in the Adirondack Mountains, U.S. It is found that, for 99 percent of the data, the maximum error is 1 degree.

Wildey, Robert L.↗

NASA NTRS1988

Hellas Basin ejecta: A prime stratigraphic marker and sampling target

The Hellas Basin and associated ejecta deposits dominate a large portion of the southern highlands of Mars. These deposits have been particularly well-documented at the scale 1:5,000,000 in the Sinus Sabaeus (MC-20), Iapygia (MC-21) and Mare Tyrrhenum (MC-22) quadrangles (1,2,3) where they have been mapped as ancient hilly and cratered material. In MC-22 the ejecta deposit is interpreted to thin from west to east, away from Hellas. In the eastern part of MC-22, the outlines of some large older craters, such as Hershel, can be seen through the thin ejecta cover and some of these buried craters even have enough relief to act as depositional traps for later mostly eolian sediments. Superposed on the ejecta is a population of numerous intermediate-sized to smaller craters which indicates the relatively old age of the ejecta deposit and causes the unit to have rather rough surface topography. Numerous small channels on steeply sloping crater rims and regionally sloping surface indicate erosion, transportation and redeposition of substantial amounts of ejecta materials, probably by aqueous fluvial processes. Numerous more recent volcanic constructs and flows also are superposed on the ejecta.

King, Elbert A.↗

NASA NTRS1987

Location of planar targets in three space from monocular images

Many pieces of existing and proposed space hardware that would be targets of interest for a telerobot can be represented as planar or near-planar surfaces. Examples include the biostack modules on the Long Duration Exposure Facility, the panels on Solar Max, large diameter struts, and refueling receptacles. Robust and temporally efficient methods for locating such objects with sufficient accuracy are therefore worth developing. Two techniques that derive the orientation and location of an object from its monocular image are discussed and the results of experiments performed to determine translational and rotational accuracy are presented. Both the quadrangle projection and elastic matching techniques extract three-space information using a minimum of four identifiable target points and the principles of the perspective transformation. The selected points must describe a convex polygon whose geometric characteristics are prespecified in a data base. The rotational and translational accuracy of both techniques was tested at various ranges. This experiment is representative of the sensing requirements involved in a typical telerobot target acquisition task. Both techniques determined target location to an accuracy sufficient for consistent and efficient acquisition by the telerobot.

Cornils, Karin↗

NASA NTRS1989

Geologic setting of an unusual Martian channel - Hypotheses on origin

Several areas within the Memnonia region of Mars have been proposed as candidate sites for a Mars sample return mission. Geologic studies of these areas made from computer-enhanced high-resolution Viking images show that an assemblage of rocks having different ages and compositions are accessible to a roving vehicle. In addition, evidence of recent fluvial episodes is indicated by small channels that incises materials emplaced during the Amazonian Period. The channel discussed in this paper is located near the highland-lowland boundary in the Memnonia MC-16SW quadrangle of Mars. It is of particular interest because of distinctive morphologic characteristics compared to other Martian channels. Although several hypotheses are advanced to explain the origin of the channel, none of the arguments are completely satisfactory. However, it is believed that water mobilized from ice in the subjacent regolith (hypothesis 1) or that condensate water from highly volatile ash flows (hypothesis 2) are the most likely origins for the channel.

Scott, D. H.↗

NASA NTRS1990

Comparison of 7.5-minute and 1-degree digital elevation models

Two digital elevation models are compared for the Echo Mountain SE quadrangle in the Cascade Mountains of Oregon. Comparisons were made between 7.5-minute (1:24,000-scale) and 1-degree (1:250,000-scale) images using the variables of elevation, slope aspect, and slope gradient. Both visual and statistical differences are presented.

Isaacson, Dennis L.↗

NASA NTRS1991

Mars geologic mapping: Dao, Harmakhis, and Reull Valles region

The east rim of Hellas basin is a complex geologic region affected by volcanic, tectonic, channeling, and resurfacing processes. A regional geologic map of the area between 27.5-42.4 degrees S and 260-275 degrees W was compiled in order to establish general stratigraphic relationships between and among the geologic units exposed in the region. The southern one-third of the regional map, the area convered by three MGM 1:500,000 quadrangles -40272, -40267, and -40262, is to be mapped in more detail in this project. Outflow channel deposits were subdivided into three facies and interpreted. A geologic sketch map of the Hadriaca Patera region on the east rim of the Hellas basin is presented.

Price, Katherine H.↗

NASA NTRS1991

A new edition of the Mars 1:5,000,000 map series

A new edition of the Mars 1:5,000,000 scale map series is in preparation. Two sheets will be made for each quadrangle. Sheet one will show shaded relief, contours, and nomenclature. Sheet 2 will be a full-color photomosaic prepared on the Mars digital image model (MDIM) base co-registered with the Mars low-resolution color database. The latter will have an abbreviated graticule (latitude/longitude ticks only) and no other line overprint. The four major databases used to assemble this series are now virtually complete. These are: (1) Viking-revised shaded relief maps at 1:5,000,000 scale; (2) contour maps at 1:2,000,000 scale; (3) the Mars digital image model; and (4) a color image mosaic of Mars. Together, these databases form the most complete planetwide cartographic definition of Mars that can be compiled with existing data. The new edition will supersede the published Mars 1:5,000,000 scale maps, including the original shaded relief and topographic maps made primarily with Mariner 9 data and the Viking-revised shaded relief and controlled photomosaic series. Publication of the new series will begin in late 1991 or early 1992, and it should be completed in two years.

Batson, R. M.↗

NASA NTRS1991

A new catalog of planetary maps

A single, concise reference to all existing planetary maps, including lunar ones, is being prepared that will allow map users to identify and locate maps of their areas of interest. This will be the first such comprehensive listing of planetary maps. Although the USGS shows index maps on the collar of each map sheet, periodically publishes index maps of Mars, and provides informal listings of the USGS map database, no tabulation exists that identifies all planetary maps, including those published by DMA and other organizations. The catalog will consist of a booklet containing small-scale image maps with superimposed quadrangle boundaries and map data tabulations.

Batson, R. M.↗

NASA NTRS1992

An unusual spectral unit in West Candor Chasma: Evidence for hydrothermal or aqueous alteration?

A spectrally distinctive unit on the floor of W. Candor Chasma (6 S, 76 W) in the central Valles Marineris may be a likely candidate for hydrothermal or aqueous alteration. This unusual material is noticeably redder than nearby plains and canyon floor-covering deposits of similar brightness in several Viking Orbiter color composite images calibrated using PICS Level I procedures. The surrounding plains and canyon floor units have colors that are typical for much of the weathered soil on Mars. Relative to adjacent materials, the West Candor unit has lower green-filter reflectance and higher red-filter reflectance. While subtle, these spectral characteristics were observed for this unit in a number of multi-spectral images acquired at different seasons and phase angles. When the color image data are transformed to hue, saturation, and value coordinates, the West Candor material stands out prominently among the rocks and soils of Coprates Quadrangle as a spatially coherent unit with a unique hue. Physically, this means that the unit is compositionally distinct (unlike most of the bright materials in the region), since its spectral reflectance cannot be obtained through simple multiplicative scaling of the reflectance of the surrounding bright materials or by altering the spectral reflectance of the surrounding materials with an additive constant that is independent of wavelength. Recent studies of the directional reflectance properties of the surface in this region indicate that the photometric phase function of the unit is similar to that of surrounding bright materials (isotropic to slightly back scattering).

Geissler, P. E.↗

NASA NTRS1992

On pose determination using point features

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.

Hwang, Vincent↗

NASA NTRS1993

Basal scarp, paleoglacier, and fissure flows of Elysium Mons, Mars

Geological mapping at 1:500,000 scale of the Granicus Valles area west of Elysium Mons (MTM quadrangles 30227, 30222, and 25227) indicates that (1) the oldest deposits in the area are Upper Hesperian lavas of the Elysium shield; (2) a basal scarp formed by Early Amazonian faulting around the northwest flank of Elysium Mons triggered growth of Elysium Fossae; (3) a glacier or an ice sheet west and north of the scarp was of long duration; (4) water and lava flows from Elysium Fossae became dominant during and after glacial recession; and (5) the last volcanic-fissure-related flows resulted in linear chains of small domes on the Elysium shield.

Chapman, Mary G.↗

NASA NTRS1993

Evidence for an ice sheet/frozen lake in Utopia Planitia, Mars

Previous workers noted evidence for a lacustrine basin in Utopia Planitia, Mars. Geomorphic features within the basin that collectively suggest that water or ice may once have been present include channels within the basin, channels peripheral to the basin, etched basin floor, 'thumbprint' terrain (whorled patterns), polygonal outlines, smooth floors (infilled), shoreline indicators (terraces, platforms, lineaments), and small cratered cones (pseudo craters or pingos). The authors interpret these data to suggest that the basin may have been the locus of a large paleolake in the northern lowlands of Mars. Alternatively, the area was proposed to be part of an ancient circumpolar ocean. The hypothetical paleolake was probably frozen to some depth. In fact, features now present at its boundaries suggest that the edges may have been frozen solid. Plains units at the southwestern boundary of Utopia Planitia show ridges that were compared with those that form at the mouths of Antarctic ice streams, thumbprint terrain, and young, high deposits having lobate margins that suggest mudflows. Thumbprint terrains were interpreted as recessional moraines, ice-pushed ridges, or subglacially eroded tunnel valleys with eroded eskers. At the east boundary of Utopia Planitia, geologic mapping at 1:500,000 scale of the Granicus Valles area (MTM quadrangles 30227, 30222, and 25227) indicates the presence of a basal scarp around the northwest flank of Elysium that formed the east boundary of an ancient ice sheet.

Chapman, M. G.↗