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At least 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1975

Skylab altimeter observations over terrain

The author has identified the following significant results. Data obtained by Skylab radar altimeter (S193) over the continental U.S.A. for pass 1 of SL-3 were analyzed to relate radar return signal parameters such as range, power, and waveform to ground track terrain features. The altimeter, which was originally designed for ocean observations, performed predictably well over terrain with moderate to low relief. The maximum return from more complex areas corresponded usually to the lower flatter regions within the seven kilometer diameter footprint. Altimeter measured heights correlated with map topography with an rms deviation of + or - 30 m for terrain topography with large height dispersion (passes 1 and 28) and + or - 5 m for slowly varying terrain (passes 16, 17, and 18). Analysis of the waveform and statistical characteristics of the individual signals indicated that larger signal power was usually related to dominantly specular reflections from patches 100 m or larger. Results established the capability of a spacecraft altimeter system to observe characteristic radar signatures for different types of terrain within the bandwidth restrictions of the AGC and range tracker loops.

Shapiro, A.↗
NASA NTRS2008

Simulating Operation of a Complex Sensor Network

Simulation Tool for ASCTA Microsensor Network Architecture (STAMiNA) ["ASCTA" denotes the Advanced Sensors Collaborative Technology Alliance.] is a computer program for evaluating conceptual sensor networks deployed over terrain to provide military situational awareness. This or a similar program is needed because of the complexity of interactions among such diverse phenomena as sensing and communication portions of a network, deployment of sensor nodes, effects of terrain, data-fusion algorithms, and threat characteristics. STAMiNA is built upon a commercial network-simulator engine, with extensions to include both sensing and communication models in a discrete-event simulation environment. Users can define (1) a mission environment, including terrain features; (2) objects to be sensed; (3) placements and modalities of sensors, abilities of sensors to sense objects of various types, and sensor false alarm rates; (4) trajectories of threatening objects; (5) means of dissemination and fusion of data; and (6) various network configurations. By use of STAMiNA, one can simulate detection of targets through sensing, dissemination of information by various wireless communication subsystems under various scenarios, and fusion of information, incorporating such metrics as target-detection probabilities, false-alarm rates, and communication loads, and capturing effects of terrain and threat.

Jennings, Esther↗
NASA NTRS1992

The topography of impact craters in 'softened' terrain on Mars

The technique of photoclinometry is applied here to Viking orbiter images of Mars in order to derive topographic profiles across Martian craters on both softened and unsoftened terrain. The results demonstrate that craters on the two kinds of terrain are in fact topographically distinct. Both simple and complex softened craters are characterized by more convex-upward crater walls than are unsoftened craters, and both simple and complex softened craters have rounder crater rims. Softened complex craters have modestly smaller crater depths than unsoftened complex craters. Both the rim heights and bowl depths are reduced, with the rim heights reduced more. Softened simple craters have much smaller crater depths than unsoftened simple craters. Both the rim heights and bowl depths are reduced, with the bowl depths reduced more.

Jankowski, David G.↗
NASA NTRS1993

Rover requirements for the planet surface segment of the space exploration initiative

Annotated requirements for rovers to be used for the First Lunar Outpost (FLO) of the Space Exploration Initiative (SEI) and for Mars missions are presented. The requirements are presented in the form of functions as opposed to performance. SEI surface systems will be required to execute many roving vehicle functions ranging from transporting humans to recovery and transporting raw materials to a processing plant. Some of the roving vehicles will be highly automated. These automation functions may include the following: teleoperated site survey and certification; teleoperation for repair; autonomous operations for resource location and mining; autonomous navigation and terrain traverse; and telerobotic scientific investigations. These requirements are complex, contradictory, and will be costly if they are not carefully analyzed and properly allocated to conceptual elements. Of greatest importance will be the iterative analysis of requirements and synergistic utilization of vehicle elements.

Roberts, Barney B.↗
NASA NTRS2005

Photo-realistic Terrain Modeling and Visualization for Mars Exploration Rover Science Operations

Modern NASA planetary exploration missions employ complex systems of hardware and software managed by large teams of. engineers and scientists in order to study remote environments. The most complex and successful of these recent projects is the Mars Exploration Rover mission. The Computational Sciences Division at NASA Ames Research Center delivered a 30 visualization program, Viz, to the MER mission that provides an immersive, interactive environment for science analysis of the remote planetary surface. In addition, Ames provided the Athena Science Team with high-quality terrain reconstructions generated with the Ames Stereo-pipeline. The on-site support team for these software systems responded to unanticipated opportunities to generate 30 terrain models during the primary MER mission. This paper describes Viz, the Stereo-pipeline, and the experiences of the on-site team supporting the scientists at JPL during the primary MER mission.

Edwards, Laurence↗
NASA NTRS1996

Tessera Terrain on Venus: A Survey of the Global Distribution, Characteristics, and Relation to Surrounding Units from Magellan Data

The tessera terrain on Venus, comprised of areas of high radar backscatter, complex deformation patterns relative to other units, and topography standing higher than surrounding plains, covers approximately 35.33 x 10(exp 6)sq km, about 8% of the surface of Venus, and is nonrandomly distributed, being preferentially located at equatorial and higher northern latitudes with a distinct paucity below about 30degS. Individual tessera occurrences range in area from the lower limits of our measurements (about 200 sq km) up to the largest tessera, Ovda, with an area of about 8.6 x 10(exp 6)sq km, or about 2% of the surface area of Venus. The size-frequency distribution of tessera patches is strongly unimodal and skewed toward smaller sizes, reflecting the great abundance of small tessera fragments. Modes of occurrence include (1) large clusters (e.g., Aphrodite Terra and Ishtar Terra); (2) arc-like segments which may extend for thousands of kilometers and are either concave inward toward the major tessera cluster development or away from it; (3) areas where tesserae are rare or absent which occur both as low-lying plains (e.g., Guinevere Planitia), and as elevated regions (e.g., Ata Regio). Tessera terrain has a bimodal elevation-frequency distribution, with the main peak at about 0- 1 km and an additional peak at about 3 km above mean planetary radius. In terms of number of occurrences, however, tesserae do not display a correlation with elevation at the global scale, since small tessera patches commonly occupy low-lying regions. Although tessera exhibit a range of gravity signatures, many occurrences are interpreted to represent relatively shallow (crustal) levels of compensation. Tessera boundaries include Type I (sinuous/embayed, dominated by adjacent lava plains embaying tessera massifs; 73% of total tesserae boundaries) and Type II (linear/tectonic). Only a small percentage of the length of all boundary types show no lava embayment and could be interpreted as tectonically active for long periods subsequent to initial tessera formation. Occurrence of broad slopes of post-tessem embayed plains away from tessera boundaries suggests that regional tilting occurred subsequent to final temra deformation in some places.

Ivanov, Mikhail↗
NASA NTRS1981

The morphology and evolution of Ganymede and Calisto

Images of Ganymede and Callisto, Jupiter's two largest moons, among the largest known predominantly icy planetary objects, were obtained by the two Voyager spacecraft. Voyager images were used to investigate the surface characteristics, geologic processes, and internal evolution of Ganymede and Callisto. Ganymede shows two principal types of terrain: one dark, old, and heavily cratered; and another brighter, younger, and characterized by complex patterns of grooves. Voyager imagers were used to determine photometric properties of surface features on both bodies at phase angles up to 120 deg. Surface temperatures are calculated for the major terrain types. Callisto is found to be somewhat warmer than Ganymede. The temperature difference between grooved and cratered terrain on Ganymede is small. A model for the origin of grooved terrain is considered in which extension creates broad, downdropped rift zones in the crust that are filled with water or ice from below.

Squyres, S. W.↗
NASA NTRS1985

Mega-geomorphology: Mars vis a vis Earth

The areas of chaotic terrain, the giant chasma of the Valles Marineris region, the complex linear and circular depressions of Labyrinthus Noctis on Mars all suggest the possibility of large scale collapse of parts of the martian crust within equatorial and sub equatorial latitudes. It seems generally accepted that the above features are fossil, being perhaps, more than a billion years old. It is possible that parts of Earth's crust experienced similar episodes of large scale collapse sometime early in the evolution of the planet.

Sharp, R. P.↗
NASA NTRS1988

Radii, shapes, and topography of the satellites of Uranus from limb coordinates

The present use of limb coordinates to ascertain radii, shape and local topographic characteristics for the five large Uranian satellites directly measured satellite ellipsoidal shapes, determining radii with subpixel accuracy. While Umbriel, Titania, and Oberon are spherical, Miranda and Ariel are noted to be ellipsoids whose equatorial bulges agree with previously determined mean densities. Miranda's topography exhibits substantial deformation of cratered terrain and the younger coronae, as well as uplift and complex faulting at coronae margins.

Thomas, P. C.↗
NASA NTRS2017

The Geology of Charon as Revealed by New Horizons

Pluto's large moon Charon [radius 606 km; density = 1.70 g cm(exp. -3)] exhibits a striking variety of landscapes. Charon can be divided into two broad provinces separated by a roughly aligned assemblage of ridges and canyons, which span from east to west. North of this tectonic belt is rugged, cratered terrain (Oz Terra); south of it are smoother but geologically complex plains (Vulcan Planum). (All place names here are informal.) Relief exceeding 20 km is seen in limb profiles and stereo topography.

Charon↗
NASA NTRS1985

An archean suture zone in the Tobacco Root Mountains? (1984) Evolution of Archean Continental Crust, SW Montana (1985)

The Lake Plateau area of the Beartooth Mountains, Montana were mapped and geochemically sampled. The allochthonous nature of the Stillwater Complex was interpreted as a Cordilleran-style continental margin. The metamorphic and tectonic history of the Beartooth Mountains was addressed. The Archean geology of the Spanish Peaks area, northern Madison Range was addressed. A voluminous granulite terrain of supracrustal origin was identified, as well as a heretofore unknown Archean batholithic complex. Mapping, petrologic, and geochemical investigations of the Blacktail Mountains, on the western margin of the Wyoming Province, are completed. Mapping at a scale of 1:24000 in the Archean rocks of the Gravelly Range is near completion. This sequence is dominantly of stable-platform origin. Samples were collected for geothermometric/barometric analysis and for U-Pb zircon age dating. The analyses provide the basis for additional geochemical and geochronologic studies. A model for the tectonic and geochemical evolution of the Archean basement of SW Montana is presented.

Mogk, D. W.↗
NASA NTRS2008

ATHLETE's Feet: Mu1ti-Resolution Planning for a Hexapod Robot

ATHLETE is a large six-legged tele-operated robot. Each foot is a wheel; travel can be achieved by walking, rolling, or some combination of the two. Operators control ATHLETE by selecting parameterized commands from a command dictionary. While rolling can be done efficiently with a single command, any motion involving steps is cumbersome - walking a few meters through difficult terrain can take hours. Our goal is to improve operator efficiency by automatically generating sequences of motion commands. There is increasing uncertainty regarding ATHLETE s actual configuration over time and decreasing quality of terrain data farther away from the current position. This, combined with the complexity that results from 36 degrees of kinematic freedom, led to an architecture that interleaves planning and execution at multiple levels, ranging from traditional configuration space motion planning algorithms for immediate moves to higher level task and path planning algorithms for overall travel. The modularity of the architecture also simplifies the development process and allows the operator to interact with and control the system at varying levels of autonomy depending on terrain and need.

Smith, Tristan B.↗
NASA NTRS1989

Fortuna Tessera, Venus - Evidence of horizontal convergence and crustal thickening

Structural and tectonic patterns mapped in Fortuna Tessera are interpreted to reflect a change in the style and intensity of deformation from east to west, beginning with simple tessera terrain at relatively low topographic elevations in the east and progressing through increasingly complex deformation patterns and higher topography to Maxwell Montes in the West. These morphologic and topographic patterns are consistent with east-to-west convergence and compression and the increasing elevations are interpreted to be due to crustal thickening processes associated with the convergent deformational environment. Using an Airy isostatic model, crustal thicknesses of approximately 35 km for the initial tessera terrain, and crustal thicknesses of over 100 km for the Maxwell Montes region are predicted. Detailed mapping with Magellan data will permit the deconvolution of individual components and structures in this terrain.

Vorder Bruegge, R. W.↗
NASA NTRS1973

Mars: Fretted and chaotic terrains

Fretted Martian terrain is characterized by smooth, flat, lowland areas separated from a cratered upland by abrupt escarpments of complex planimetric configuration and a maximum estimated height approaching 1 to 2 km. It is the product of some unusual erosive or abstractive process that has created steep escarpments. Chaotic terrain differs from fretted terrain in having a rough floor topography featuring a haphazard jumble of large angular blocks, and by arc-shaped slump blocks on its bounding escarpments. Its existence has now been confirmed by Mariner 9 pictures, and the characteristics, location, and areal extent of chaotic terrain have been more accurately and completely defined.

Sharp, R. P.↗
NASA NTRS2008

Mapping the Sedna-Lavinia Region of Venus

Geologic mapping of Venus at 1:5 M scale has shown in great detail the flow complexes of volcanoes, coronae, and shield fields, and the varying structural patterns that differentiate tesserae from corona rims and isolated patches of densely lineated terrain. In most cases, however, the lower-elevation plains between the higher-standing landforms are discriminated only on the basis of potentially secondary features such as late-stage lava flooding or tectonic overprinting. This result, in which volcanoes and tesserae appear as "islands in the sea," places weak constraints on the relative age of large upland regions and the nature of the basement terrain. In this work, we focus on the spatial distribution and topography of densely lineated and tessera units over a large region of Venus, and their relationship to apparently later corona and shield flow complexes. The goal is to identify likely connections between patches of deformed terrain that suggest earlier features of regional extent, and to compare the topography of linked patches with other such clusters as a guide to whether they form larger tracts beneath the plains. Mapping Approach. We are mapping the region from 57S to 57N, 300E-60E. Since the 1:5 M quadrangles emphasize detail of tessera structure and corona/edifice flows, we simply adopt the outlines of these features as they relate to the outcrops of either "densely lineated terrain" or tessera (Fig. 1). The densely lineated material is mapped in many quadrangles based on pervasive structural deformation, typically with a single major axis (in contrast to the overlapping orthogonal patterns on tesserae). This unit definition is often extended to include material of corona rims. We do not at present differentiate between plains units, since earlier efforts show that their most defining attributes may be secondary to the original emplacement (e.g., lobate or sheet-like flooding by thin flow units, tectonic patterns related to regional and localized stress regimes) [1].

Campbell, Bruce A.↗
NASA NTRS1979

Mars - CO2 adsorption and capillary condensation on clays: Significance for volatile storage and atmospheric history

Results on the adsorbate-adsorbent system CO2-nontronite are reported at 230, 196, and 158 deg K, covering the range of subsurface regolith temperature on Mars. A three-part regolith-atmosphere-cap model reveals that cold nontronite, and expanding clays in general, are far better but far more complex CO2 adsorbers than cold pulverized basalt. In addition, the layered terrain, and possibly the adjacent debris mantle, contains about 2% or more by mass of atmosphere-exchangeable CO2 and the total regolith inventory of available adsorbed CO2 is estimated to be 400 g/ sq cm.

Fanale, F. P.↗
NASA NTRS2004

Crustal Evolution of the Protonilus Mensae Area, Mars

Despite research by numerous geologists and geo- physicists, the age and origin of the martian crustal dichotomy remain uncertain. Models for the origin of this dichotomy involve single or multiple impact, mantle megaplumes, primordial crustal asymmetry, and plate tectonics. Most of these models imply a Noachian age for the dichotomy. A major problem common to all genetic models is the difficulty separating the features resulting from the primary cause for the dichotomy from features due to younger fault- ing, impact cratering, volcanism, deposition, and erosion. highlands (the dichotomy boundary) approximates a small circle that ranges in latitude from about -10 deg. in Elysium Planitia to about +45 deg. north of Arabia Terra. For much of its length the boundary is characterized by relatively steep scarps separating highland plateau to the south from lowland plains to the north, generally with a complex transition zone on the lowland side of these scarps. These scarps are almost certainly due to normal faulting. The type fretted terrain, which defines the boundary in north-central Arabia Terra, also is characterized by scarps but has under- gone a more complex history of faulting and dissection [13]. In some places, notably in the Acidalia Planitia region, the dichotomy boundary is gradational. In the Tharsis region the boundary is obscured by younger volcanics.

McGill, G. E.↗
NASA NTRS2009

NASA Tech Briefs, August 2009

Topics covered include: Aligning a Receiving Antenna Array to Reduce Interference; Collecting Ground Samples for Balloon-Borne Instruments; Tethered Pyrotechnic Apparatus for Acquiring a Ground Sample; Enhanced Video-Oculography System; Joint Carrier-Phase Synchronization and LDPC Decoding; Dual-Polarization, Sideband-Separating, Balanced Receiver for 1.5 THz Modular Battery Charge Controller; Efficient Multiplexer FPGA Block Structures Based on G4FETs; VLSI Microsystem for Rapid Bioinformatic Pattern Recognition; Low-Noise Amplifier for 100 to 180 GHz; Improved Fabrication of Ceramic Matrix Composite/Foam Core Integrated Structures; Inert Welding/Brazing Gas Filters and Dryers; Fabricating Copper Nanotubes by Electrodeposition; Reducing Aerodynamic Drag on Empty Open Cargo Vehicles; Rotary Percussive Auto-Gopher for Deep Drilling and Sampling; More About Reconfigurable Exploratory Robotic Vehicles; Thermostatic Valves Containing Silicone-Oil Actuators; Improving Heat Flux Performance of Flat Surface in Spray-Cooling Systems; Treating Fibrous Insulation to Reduce Thermal Conductivity; Silica-Aerogel Composites Opacified with La(sub0.7)Sr(sub0.3)MnO3; Cyclic Oxidation Behavior of CuCrAl Cold-Sprayed Coatings for Reusable Launch Vehicles; Ceramic Fiber Structures for Cryogenic Load-Bearing Applications; Elastomer Reinforced with Carbon Nanotubes; Biologically Inspired Purification and Dispersion of SWCNTs; A Technique for Adjusting Eigenfrequencies of WGM Resonators; Low-Pressure, Field-Ionizing Mass Spectrometer; Modifying Operating Cycles to Increase Stability in a LITS; Chamber for Simulating Martian and Terrestrial Environments; Algorithm for Detecting a Bright Spot in an Image; Extreme Programming: Maestro Style; Adaptive Behavior for Mobile Robots; Protocol for Communication Networking for Formation Flying; Planning Complex Sequences Using Compressed Representations; and Self-Supervised Learning of Terrain Traversability from Proprioceptive Sensors.

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