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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1993

Local topography of Mars and its relationship to surface weathering processes

There is a growing body of evidence in favor of the importance of aqueous sedimentary processes on Mars. It is important to understand the role that surface weathering processes have played in the development of the present morphology of the Martian surface. Such an understanding is important not only for its relevance to the study of volatile sources and sinks on Mars through time, but also for its relevance to Martian geologic and tectonic history. Starting in the fall of this year, the Mars Observer Laser Altimeter will begin sending back to Earth data on the topography of Mars that is of a higher quality than most of the topography data available for the Earth. This data will be invaluable, not only for understanding global and large-scale regional processes and landforms on Mars, but also for the study of local and smaller-scale regional processes and landforms. Digital topography is an important part of geologic and geomorphic studies, useful in distinguishing between different lithologies and between different types of weathering. Digital topography data may be used to study a wide variety of local and regional-scale landforms, including valleys, sand dunes, lava flows, landslides, and slopes. Topography data are also essential to the analysis of spectral response patterns, especially in areas of high topographic relief. Geomorphic classification can be significantly improved by the addition of topographic information.

Schaefer, M. W.↗
NASA NTRS1992

Geological correlations with the interior density structure of Venus

The paper develops a geophysical model for Venus that allows separation of topography supported by shallow density anomalies, e.g., crustal thickening, from that interpreted to be caused by mantle convection, and produces estimates of the planforms of lithospheric density anomalies and the mantle convection pattern. The topography caused by these two planforms is compared to several global data sets compiled from analysis of Magellan data. The mantle convection pattern agrees qualitatively with numerical simulations by Bercovici et al. (1989) and shows isolated upwellings amidst a network of downwellings. Crustal thickening does not exhibit a similar pattern. Impact crater density is nearly uniform and does not correlate with either crustal thickening or the mantle convection patterns. Large volcanic structures exhibit a good but imperfect correlation with mantle upwellings. Coronae locations are anticorrelated with large upwellings and large downwellings. A scenario is proposed for global tectonics on Venus and its relationship to mantle convection.

Herrick, Robert R.↗
NASA NTRS2001

Idealized Simulations of the Effects of Amazon Convection and Baroclinic Waves on the South Atlantic Convergence Zone

The South Atlantic Convergence Zone (SACZ) is a NW-SE oriented, stationary region of enhanced convergence and convection that extends southeastward from the ITCZ convection anchored over the Amazon region. On daily satellite images each SACZ episode is seen as a progression of one or several midlatitude cold fronts that intrude into the subtropics and tropics, becoming stationary over southeastern Brazil for a few days. Previous studies have shown that while Amazon convection plays a fundamental role in the formation of the SACZ, Atlantic sea surface temperatures and the Andes Mountains play a relatively minor role in the strength and location of the SACZ. The role of interactions between Amazon convection and midlatitude baroclinic waves in establishing the origin, position, and maintenance of the SACZ is studied here using idealized dry, multilayer global model simulations that do not include the effects of topography. The model simulations produce SACZ-like regions of low-level convergence in the presence of Amazon convection embedded in a mean-flow that contains propagating baroclinic waves. The results of these simulations indicate that Amazon convection plays two fundamental roles in the formation and location of the SACZ. First, it produces a NW-SE oriented region of low-level convergence to the SE of Amazon convection. Second, it produces a storm-track region and accompanying stronger midlatitude baroclinic waves in the region of the SACZ. It is suggested that in the presence of moist effects, the 'seedling' SACZ regions produced in these simulations can be enhanced to produce the observed SACZ.

Ferreira, Rosana Nieto↗
NASA NTRS2008

Volcanic Gas Emissions Mapping Using a Mass Spectrometer System

The visualization of hazardous gaseous emissions at volcanoes using in-situ mass spectrometry (MS) is a key step towards a better comprehension of the geophysical phenomena surrounding eruptive activity. In-Situ gas data consisting of helium, carbon dioxide, sulfur dioxide, and other gas species, were acquired with an MS system. MS and global position system (GPS) data were plotted on ground imagery, topography, and remote sensing data collected by a host of instruments during the second Costa Rica Airborne Research and Technology Applications (CARTA) mission This combination of gas and imaging data allowed 3-dimensional (3-D) visualization of the volcanic plume end the mapping of gas concentration at several volcanic structures and urban areas This combined set of data has demonstrated a better tool to assess hazardous conditions by visualizing and modeling of possible scenarios of volcanic activity. The MS system is used for in-situ measurement of three-dimensional gas concentrations at different volcanic locations with three different transportation platforms, aircraft, auto, and hand carried. The demonstration for urban contamination mapping is also presented as another possible use for the MS system.

Griffin, Timothy P.↗
NASA NTRS2013

KARIN: The Ka-Band Radar Interferometer for the Proposed Surface Water and Ocean Topography (SWOT) Mission

Over the last two decades, several nadir profiling radar altimeters have provided our first global look at the ocean basin-scale circulation and the ocean mesoscale at wavelengths longer than 100 km. Due to sampling limitations, nadir altimetry is unable to resolve the small wavelength ocean mesoscale and sub-mesoscale that are responsible for the vertical mixing of ocean heat and gases and the dissipation of kinetic energy from large to small scales. The proposed Surface Water and Ocean Topography (SWOT) mission would be a partnership between NASA, CNES (Centre National d'Etudes Spaciales) and the Canadian Space Agency, and would have as one of its main goals the measurement of ocean topography with kilometer-scale spatial resolution and centimeter scale accuracy. In this paper, we provide an overview of all ocean error sources that would contribute to the SWOT mission.

Ka-Band Radar Interferometer (KaRIn) instrument↗
NASA NTRS2001

The Mars Orbiter Altimeter (MOLA) Investigation of the Shape and Topography of Mars

The Mars Orbiter Laser Altimeter (MOLA) is an instrument on the Mars Global Surveyor (MGS) spacecraft that has been orbiting Mars since September 1997. After some preliminary observations in Sept/Oct, 1997 and in the spring and summer of 1998, the MGS spacecraft entered its mapping orbit of 400 km above the surface of Mars in February 1999. MGS began a 2 year program of systematically mapping the planet with a camera (MOC), thermal emission spectrometer (TES), magnetometer (MAG), laser altimeter (MOLA), and a radio science investigation for gravity and radio occultations. MOLA has a 48mJ, 1064 nrn ND:YAG, diode pumped laser with a 8 nanosecond pulse width, a pulse rate of 10 Hz, and a range precision of less than 40 cm. MOLA has been operating almost continuously for over two years and obtained over 600 million measurements of the radius of Mars. Using very precise orbits for the MGS spacecraft derived from the Doppler and range tracking of MGS by the Deep Space Network a topographical map of Mars has been developed with an average radial accuracy of a meter and a horizontal accuracy of 100 meters. This topographical map has revealed a new Mars, a planet with some of the flattest areas in the solar system and one of the largest impact basins. MOLA has revealed clear evidence of the effect of past fluid action on the surface and found icecaps that contain as much water ice today as the icecap of Greenland.

Smith, David E.↗
NASA NTRS2004

A new Mars radiation environment model with visualization

A new model for the radiation environment to be found on the planet Mars due to Galactic Cosmic Rays (OCR) has been developed at the NASA Langley Research Center. Solar modulated primary particles rescaled for Mars conditions are transported through the Martian atmosphere, with temporal properties modeled with variable timescales, down to the surface, with altitude and backscattering patterns taken into account. The Martian atmosphere has been modeled by using the Mars Global Reference Atmospheric Model--version 2001 (Mars-GRAM 2001). The altitude to compute the atmospheric thickness profile has been determined by using a model for the topography based on the data provided by the Mars Orbiter Laser Altimeter (MOLA) instrument on board the Mars Global Surveyor (MGS) spacecraft. The Mars surface composition has been modeled based on averages over the measurements obtained from orbiting spacecraft and at various landing sites, taking into account the possible volatile inventory (e.g., CO2 ice, H2O ice) along with its time variation throughout the Martian year. Particle transport has been performed with the HZETRN heavy ion code. The Mars Radiation Environment Model has been made available worldwide through the Space Ionizing Radiation Effects and Shielding Tools (SIREST) website, a project of NASA Langley Research Center. c2004 COSPAR. Published by Elsevier Ltd. All rights reserved.

NASA Center LaRC↗
NASA NTRS1995

Satellite Observations of Atmospheric Gravity Waves

The Microwave Limb Sounder (MLS) on the Upper Atmosphere Research Satellite produced the first global maps of small-scale gravity wave variances in the middle atmosphere. Observations at 30-88 km altitudes show that the variances of 30-100 km horizontal scales are strongly correlated with surface topography and stratospheric jet streams. The several years of MLS data will provide a climatology of global gravity wave activity needed for modeling atmospheric circulations and mixing processes.

atmospheric gravity waves middle atmosphere Microw↗
NASA NTRS1985

Venus Gravity: Global Field Results

The Pioneer Venus Orbiter has provided a vast amount of gravity data, since March 1979. High resolution results have revealed the high correlation between topography and gravity. These data were acquired at relatively low spacecraft altitudes (150 km) where atmospheric effects and high frequency variations were significant and modelling with global spherical harmonics was difficult. During 1982 data were acquired over a complete Venus rotation where the lowest altitudes were 1000 km or more, thus removing atmospherics and high frequency gravity effects. These data that have been reduced to produce a tenth degree and order spherical harmonic model of the global gravity field of Venus. The reduction technique used a least squares where 78 independent arcs of data were combined in a simultaneous inversion. The tenth degree and order gravity field solution has 117 parameters describing the spherical harmonic coefficients. This provides approximately 1800 km feature resolution. These coefficients are presented as a geoid map.

Mottinger, N. A.↗
NASA NTRS1978

Emergence of the continents

If early degassing of the Earth produced a global ocean several km deep overlying a global sialic crust, then late heavy bombardment of that crust by basin forming impacting bodies would have produced topography such that by 4 billion years ago dry continential landmasses would stand above sea level. From extrapolation of lunar crater statistics, at least 50% of an original global crust on the earth would have been converted into basins averaging 4 km deep after isostatic adjustment. These basins formed the sink into which such a global ocean would drain. If the ocean was initially 2 km deep, then approximately 50% of the early Earth would have stood above sea level when the late heavy bombardment came to a close.

Frey, H.↗
NASA NTRS1978

An investigation of the astronomical theory of the ice ages using a simple climate-ice sheet model

The astronomical theory of the Quaternary ice ages is incorporated into a simple climate model for global weather; important features of the model include the albedo feedback, topography and dynamics of the ice sheets. For various parameterizations of the orbital elements, the model yields realistic assessments of the northern ice sheet. Lack of a land-sea heat capacity contrast represents one of the chief difficulties of the model.

Pollard, D.↗
NASA NTRS1979

Photogrammetric portrayal of Mars topography

Special photogrammetric techniques have been developed to portray Mars topography, using Mariner and Viking imaging and nonimaging topographic information and earth-based radar data. Topography is represented by the compilation of maps at three scales: global, intermediate, and very large scale. The global map is a synthesis of topographic information obtained from Mariner 9 and earth-based radar, compiled at a scale of 1:25,000,000 with a contour interval of 1 km; it gives a broad quantitative view of the planet. At intermediate scales, Viking Orbiter photographs of various resolutions are used to compile detailed contour maps of a broad spectrum of prominent geologic features; a contour interval as small as 20 m has been obtained from very high resolution orbital photography. Imagery from the Viking lander facsimile cameras permits construction of detailed, very large scale (1:10) topographic maps of the terrain surrounding the two landers; these maps have a contour interval of 1 cm. This paper presents several new detailed topographic maps of Mars.

Wu, S. S. C.↗
NASA NTRS1981

Observations and models of inertial waves in the deep ocean

A study of the structure of the inertial peak in deep ocean kinetic energy is presented, based on records taken from Polymode arrays deployed in the western North Atlantic Ocean. Results are interpreted in terms of both local sources and turning point effects on internal waves generated at lower latitudes, and it is found that three classes of environment and their corresponding spectra emerge from peak height variations: (1) the 1500-m level near the Mid-Atlantic Ridge, with the greatest peak height of 18 dB; (2) the upper and deep ocean over rough topography and the deep ocean underneath the Gulf Stream, with the intermediate peak height of 11.5 dB; and (3) the deep ocean over smooth topography, with the lowest peak height of 7.5 dB. Using the globally valid wave functions obtained by Munk and Phillips (1968), frequency spectra near f are calculated numerically. The model is latitudinally dependent, with the frequency shift and bandwidth of the inertial peak decreasing with latitude.

Fu, L.-L.↗
NASA NTRS1988

Mars Observer - Science

The scientific objectives and experiments planned for the Mars Observer mission are discussed. Scientific instruments for the mission are described and illustrated, including a gamma-ray spectrometer, a visual and IR mapping spectrometer, a thermal emission spectrometer, an imaging camera, a radar altimeter and radiometer, a magnetometer, and a pressure modulate IR radiometer. Mission objectives include studying the global elemental and mineralogical character of the Martian surface, defining the topography and gravitational field, studying the atmospheric circulation, and determining the time and space distribution, abundance sources, and sinks of volatile material and dust over a seasonal cycle.

Albee, Arden L.↗
NASA NTRS1992

Lunar Observer Laser Altimeter observations for lunar base site selection

One of the critical datasets for optimal selection of future lunar landing sites is local- to regional-scale topography. Lunar base site selection will require such data for both engineering and scientific operations purposes. The Lunar Geoscience Orbiter or Lunar Observer is the ideal precursory science mission from which to obtain this required information. We suggest that a simple laser altimeter instrument could be employed to measure local-scale slopes, heights, and depths of lunar surface features important to lunar base planning and design. For this reason, we have designed and are currently constructing a breadboard of a Lunar Observer Laser Altimeter (LOLA) instrument capable of acquiring contiguous-footprint topographic profiles with both 30-m and 300-m along-track resolution. This instrument meets all the severe weight, power, size, and data rate limitations imposed by Observer-class spacecraft. In addition, LOLA would be capable of measuring the within-footprint vertical roughness of the lunar surface, and the 1.06-micron relative surface reflectivity at normal incidence. We have used airborne laser altimeter data for a few representative lunar analog landforms to simulate and analyze LOLA performance in a 100-km lunar orbit. We demonstrate that this system in its highest resolution mode (30-m diameter footprints) would quantify the topography of all but the very smallest lunar landforms. At its global mapping resolution (300-m diameter footprints), LOLA would establish the topographic context for lunar landing site selection by providing the basis for constructing a 1-2 km spatial resolution global, geodetic topographic grid that would contain a high density of observations (e.g., approximately 1000 observations per each 1 deg by 1 deg cell at the lunar equator). The high spatial and vertical resolution measurements made with a LOLA-class instrument on a precursory Lunar Observer would be highly synergistic with high-resolution imaging datasets, and will allow for direct quantification of critical slopes, heights, and depths of features visible in images of potential lunar base sites.

Garvin, James B.↗
NASA NTRS1993

Coupled land surface/hydrologic/atmospheric models

The topics covered include the following: prototype land cover characteristics data base for the conterminous United States; surface evapotranspiration effects on cumulus convection and implications for mesoscale models; the use of complex treatment of surface hydrology and thermodynamics within a mesoscale model and some related issues; initialization of soil-water content for regional-scale atmospheric prediction models; impact of surface properties on dryline and MCS evolution; a numerical simulation of heavy precipitation over the complex topography of California; representing mesoscale fluxes induced by landscape discontinuities in global climate models; emphasizing the role of subgrid-scale heterogeneity in surface-air interaction; and problems with modeling and measuring biosphere-atmosphere exchanges of energy, water, and carbon on large scales.

Pielke, Roger↗