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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 487 records · Page 27
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

Thermal optical surface properties and high-temperature solar energy conversion

The effects of thermal surface properties on the performance of representative point focusing solar power plants are assessed in this paper. The tradeoff relationships are presented in terms of normalized system performance as a function of thermal optical design parameters. Crucial surface properties include solar reflectance, specular spreading due to microscopic roughness, surface error due to manufacturing slope tolerance or waviness and concentrator pointing accuracy. Two representative power conversion systems, a Rankine steam cycle and an open air Brayton cycle, are considered.

Wen, L.↗
NASA NTRS1975

Correlation of Al/Si X-ray fluorescence data with other remote sensing data from the Taurus-Littrow area

Al/Si intensity ratios from the Apollo 15 X-ray fluorescence experiment have been analyzed in conjunction with such other remote-sensing data as visible albedo measurements, color-difference photographs, and relative spectral reflectivity curves for the purpose of defining geochemical units in the Taurus-Littrow area. A geochemical boundary between the dark-mantle unit and the western edge of the Taurus Mountains is indicated by all the remote-sensing techniques considered. The major component of the ejecta from Catena Littrow, located within the dark-mantle unit, is highland-type material. The areal extent of the ejecta determined from the Al/Si data is at least 30 km along the Apollo 15 ground track. The constraint imposed upon depth to high-alumina material at Catena Littrow is 520 m. If the high-alumina material excavated at Catena Littrow is an extension of the Taurus Mountain 'roots', then the maximum slope of the buried highland surface from Catena Littrow to the Taurus Mountains border is less than 2.0 deg

Andre, C. G.↗
NASA NTRS1980

Topographic domes on Ganymede - Ice vulcanism or isostatic upwarping

Two formation processes are considered for two gently sloping domeshaped features on the surface of Ganymede, lying on grooved terrain and having diameters of roughly 250 km: (1) water vulcanism, triggered by a major impact, and (2) the isostatic upwarping of a crater formed in a thin crust. Numerical simulations show the volume of the domes to be consistent with eruption through fractures created by an impact that excavates partly through a thin crust. Isostatic upwarp rates calculated as a function of effective crustal temperature indicate that upwarping could also create such a dome if the impact excavated to a depth where the crust was sufficiently warm and mobile. Morphologic evidence suggests that both processes may have been important and, if either of the proposed models is correct, it is strongly implied that grooved terrain formation occurred prior to the thickening and stiffening of Ganymede's crust.

Squyres, S. W.↗
NASA NTRS1981

The structure of short gravity waves on the ocean surface

A brief review is given of the salient properties of short gravity waves and the way in which their structure is modified by longer waves or swell, by variable currents, and by internal waves. It is noted that an underlying swell produces a mottled pattern in synthetic aperture radar (SAR) imagery, and an expression is derived giving the fractional modulation in backscattering cross section of the ocean surface in terms of the slope of an underlying swell, the wind direction, and the direction of swell propagation relative to the angle of observation. The expression provides the possibility in appropriate circumstances of estimating the swell slope by remote sensing, in addition to the wavelength and direction of propagation, which can be measured directly from the imagery. An account is also given of the refraction of waves in variable currents and internal waves.

Phillips, O. M.↗
NASA NTRS1983

A non-Gaussian statistical model for surface elevation of nonlinear random wave fields

Probability density function of the surface elevation of a nonlinear random wave field is obtained. The wave model is based on the Stokes expansion carried to the third order for both deep water waves and waves in finite depth. The amplitude and phase of the first-order component of the Stokes wave are assumed to be Rayleigh and uniformly distributed and slowly varying, respectively. The probability density function for the deep water case was found to depend on two parameters: the root-mean-square surface elevation and the significant slope. For water of finite depth, an additional parameter, the nondimensional depth, is also required. An important difference between the present result and the Gram-Charlier representation is that the present probability density functions are always nonnegative. It is also found that the 'constant' term in the Stokes expansion, usually neglected in deterministic studies, plays an important role in determining the details of the density function. The results compare well with laboratory and field experiment data.

Huang, N. E.↗
NASA NTRS1990

Microwave scattering from wind- and rain-roughened seas

Microwave scattering from wind- and rain-roughened seas is studied under the assumption that, for light wind and light rain, the processes contributing to the scatterometer signal are independent. It is argued that calibrations from exclusively rain and exclusively wind conditions are all that is needed to predict scatterometer cross section for combined conditions. It is demonstrated that scatterometer response to a rain-roughened water surface is linear, but the slope of the relationship is sensitive to drop-size distribution. It is concluded that first-order wind and rain can be regarded as independent processes. Average cross section varies linearly with rainfall rate, but the slope of the relationship is a function of drop-size distribution. For combined light rain plus light wind, sigma-c is found to be well predicted by the addition of wind and rain models.

Bliven, Larry F.↗
NASA NTRS1992

The optical spectrum of 5145 Pholus

A 2.4-m telescope and a CCD spectrograph have been used to measure the optical reflectance spectrum of the 5145 Pholus outer solar system object in the 4400-9600 A range, with 10 A/pixel dispersion. No emission lines were detected, and a reflectance slope value intermediate between two previously reported slopes is obtained. This steep red slope is indicative of organic surface material, prompting the suggestion that the object is of primitive composition and at either the initial or terminal state of its thermal evolution.

Binzel, Richard P.↗
NASA NTRS1998

Re-Observing the First Hours of Supernova 1987A

This project was designed to use archival data from the International Ultraviolet Explorer (IUE) to measure the flux from the shock breakout from SN 1987A, emitted in the first few hours of the event, reflected from neighboring dust clouds in the form of a light echo. Such hot flux from the initial moments of a SN had never been observed before, and this offers a unique opportunity to measure it in reflection. Gilmozzi (1991, in "SN 1987A and Other Supernova") had reported such a detection of using IUE from observations made in 1988 and 1989. Our analysis of these data showed that this detection was very weak, and subject to changes comparable to the size of the signal according to various reasonable means of extracting the spectra. In fact, the features reported by Gilmozzi (1998 in "Ultraviolet Astrophysics Beyond IUE") are not found in a conventional NEWSIPS extraction or extended-source extraction of these data. The 1995 and 1996 IUE data collected for Crotts and Gilmozzi shows a more robust signal (about 20sigma,) from a cloud that echoes brighter in the optical than the 1988 feature. This shows a well-detected signal of about 5 x 10(exp -16) ergs per s/sq cm/Angstroms/arc sq sec at 1300 Angstroms, with a declining slope to redder wavelengths. This surface brightness, while detected with confidence in both large and small SVVT apertures, is still fainter than the reflected flux expected for most models of shock breakout. We have also taken the opportunity to recover the echo signal from exposures taken on Astro-1 and Astro-2 flights of the Ultraviolet Imaging Telescope (UIT) while pointed towards SN 1987A. These data yield a complementary result on the reflected flux, an upper limit of about 5 x 10(exp -17) ergs per s/sq cm/Angstroms/arc sq sec, spread over fainter optically echoing clouds, and over the same band where the signal was detected by IUE. While this appears in contradiction with the IUE result, it is made consistent by the corresponding strengths of the echoes in the optical.

Crotts, Arlin P. S.↗
NASA NTRS2004

High-Resolution Topomapping of Mars: Life After MER Site Selection

In this abstract we describe our ongoing use of high-resolution images from the Mars Global Surveyor Mars Orbiter Camera Narrow-Angle subsystem (MGS MOC-NA) to derive quantitative topographic and slope data for the martian surface at 3 - 10-m resolution. Our efforts over the past several years focused on assessment of candidate landing sites for the Mars Exploration Rovers (MER) and culminated in the selection of sites in Gusev crater and Meridiani Planum as safe as well as scientifically compelling. As of this writing, MER-A (Spirit) has landed safely in Gusev and we are performing a limited amount of additional mapping near the landing point to support localization of the lander and rover operations planning. The primary focus of our work, however, has been extending our techniques to sample a variety of geologic terrains planetwide to support both a variety of geoscientific studies and planning and data analysis for missions such as Mars Express, Mars Reconnaissance Orbiter, and Phoenix.

Kirk, R. L.↗
NASA NTRS2005

Northern Hemisphere Gullies on Mars: Analysis of Spacecraft Data and Implications for Formation Mechanisms

The origin of geologically recent gullies on Mars has remained controversial since the discovery of these features by Malin and Edgett in 2000. Numerous models have been proposed which invoke various physical processes as well as various agents of erosion to explain the origin of the Martian gullies. Hypotheses to explain the formation of the gullies invoke shallow liquid water aquifers, deep liquid water aquifers, melting ground ice, snowmelt, dry landslides, and carbon dioxide aquifers. We test the validity of such gully formation mechanisms by analyzing data from the Mars Global Surveyor and Mars Odyssey spacecrafts to uncover trends in the dimensional and physical properties of the gullies and their surrounding terrain. A similar study has previously been completed for gullies located in the southern hemisphere of Mars. The work presented here focuses exclusively on gullies in the northern hemisphere based on the identification of 136 Mars Orbiter Camera (MOC) images containing clear evidence of gully landforms, distributed in the northern mid and high latitudes. These sites have been analyzed in combination with Mars Orbiter Laser Altimeter (MOLA), Thermal Emission Spectrometer (TES), and Gamma Ray Spectrometer (GRS) data to provide quantitative measurements of numerous gully characteristics. Parameters measured include apparent source depth and distribution, vertical and horizontal dimensions, slopes, compass orientations, near-surface ice content, and factors controlling present-day climatic conditions.

Heldmann, J. L.↗
NASA NTRS2006

An Experimental Global Monitoring System for Rainfall-triggered Landslides using Satellite Remote Sensing Information

Landslides triggered by rainfall can possibly be foreseen in real time by jointly using rainfall intensity-duration thresholds and information related to land surface susceptibility. However, no system exists at either a national or a global scale to monitor or detect rainfall conditions that may trigger landslides due to the lack of extensive ground-based observing network in many parts of the world. Recent advances in satellite remote sensing technology and increasing availability of high-resolution geospatial products around the globe have provided an unprecedented opportunity for such a study. In this paper, a framework for developing an experimental real-time monitoring system to detect rainfall-triggered landslides is proposed by combining two necessary components: surface landslide susceptibility and a real-time space-based rainfall analysis system (http://trmm.gsfc.nasa.aov). First, a global landslide susceptibility map is derived from a combination of semi-static global surface characteristics (digital elevation topography, slope, soil types, soil texture, and land cover classification etc.) using a GIs weighted linear combination approach. Second, an adjusted empirical relationship between rainfall intensity-duration and landslide occurrence is used to assess landslide risks at areas with high susceptibility. A major outcome of this work is the availability of a first-time global assessment of landslide risk, which is only possible because of the utilization of global satellite remote sensing products. This experimental system can be updated continuously due to the availability of new satellite remote sensing products. This proposed system, if pursued through wide interdisciplinary efforts as recommended herein, bears the promise to grow many local landslide hazard analyses into a global decision-making support system for landslide disaster preparedness and risk mitigation activities across the world.

Hong, Yang↗
NASA NTRS2016

Lunar Reconnaissance Orbiter Camera Observations Relating to Science and Landing Site Selection in South Pole-Aitken Basin for a Robotic Sample Return Mission

The Moon's South Pole-Aitken basin (SPA) is a high priority target for Solar System exploration, and sample return from SPA is a specific objective in NASA's New Frontiers program. Samples returned from SPA will improve our understanding of early lunar and Solar System events, mainly by placing firm timing constraints on SPA formation and the post-SPA late-heavy bombardment (LHB). Lunar Reconnaissance Orbiter Camera (LROC) images and topographic data, especially Narrow Angle Camera (NAC) scale (1-3 mpp) morphology and digital terrain model (DTM) data are critical for selecting landing sites and assessing landing hazards. Rock components in regolith at a given landing site should include (1) original SPA impact-melt rocks and breccia (to determine the age of the impact event and what materials were incorporated into the melt); (2) impact-melt rocks and breccia from large craters and basins (other than SPA) that represent the post-SPA LHB interval; (3) volcanic basalts derived from the sub-SPA mantle; and (4) older, "cryptomare" (ancient buried volcanics excavated by impact craters, to determine the volcanic history of SPA basin). All of these rock types are sought for sample return. The ancient SPA-derived impact-melt rocks and later-formed melt rocks are needed to determine chronology, and thus address questions of early Solar System dynamics, lunar history, and effects of giant impacts. Surface compositions from remote sensing are consistent with mixtures of SPA impactite and volcanic materials, and near infrared spectral data distinguish areas with variable volcanic contents vs. excavated SPA substrate. Estimating proportions of these rock types in the regolith requires knowledge of the surface deposits, evaluated via morphology, slopes, and terrain ruggedness. These data allow determination of mare-cryptomare-nonmare deposit interfaces in combination with compositional and mineralogical remote sensing to establish the types and relative proportions of materials expected at a given site. Remote sensing compositions, e.g., FeO, also constrain the relative abundances of components. Landing-site assessments use crater and boulder distributions, and slope and terrain rugge

Jolliff, B. L.↗
NASA NTRS2022

Washington, D.C. & Maryland Energy: Estimating Solar Potential Using NASA POWER Data to Inform Renewable Energy Policy for Washington, D.C.

In line with the Sustainable D.C. 2.0 plan to combat climate change, Washington D.C. aims to decrease its greenhouse gas emissions by 100% by 2050. As solar energy is a clean, renewable energy form, its integration into the region’s power grids lowers energy costs and incentivizes sustainable development. We partnered with the Washington D.C. Department of Energy & Environment (DOEE) to determine how urban areas surrounding D.C. can better be incorporated into decisions regarding renewable energy policy. The team used NASA’s Prediction of Worldwide Energy Resources (POWER) solar data and a Light Detection and Ranging (LiDAR) derived digital surface model, to estimate and visualize rooftop solar potential for Maryland’s Prince George’s and Montgomery counties. POWER provided solar irradiance data adjusted for tilt angle while the digital surface model contributed aspect and slope data. This methodology factored out areas that were unsuitable for solar panel installation while displaying areas that possess a high potential for energy return. The team found the total rooftop solar potential for the study area to be almost 32 million kW, which is equivalent to roughly 660 kW per building. The methodology used to generate the solar potential maps can be applied to other regions of the country seeking to efficiently utilize solar energy. The end users at the DOEE can use our resulting solar potential map and data table to effectively target buildings that have the highest potential to generate solar energy.

Edward Cronin↗
DOE OSTI2023

Topographic hydro-conditioning to resolve surface depression storage and ponding in a fully distributed hydrologic model

Land surface depressions play a central role in the transformation of rainfall to ponding, infiltration and runoff, yet digital elevation models (DEMs) used by spatially distributed hydrologic models that resolve land surface processes rarely capture land surface depressions at spatial scales relevant to this transformation. Methods to generate DEMs through processing of remote sensing data, such as optical and light detection and ranging (LiDAR) have favored surfaces without depressions to avoid adverse slopes that are problematic for many hydrologic routing methods. Here, in this study, we present a new topographic conditioning workflow, Depression-Preserved DEM Processing (D2P) algorithm, which is designed to preserve physically meaningful surface depressions for depression-integrated and efficient hydrologic modeling. D2P includes several features: (1) an adaptive screening interval for delineation of depressions, (2) the ability to filter out anthropogenic land surface features (e.g., bridges), (3) the ability to blend river smoothing (e.g., a general downslope profile) and depression resolving functionality. From a case study in the Goodwin Creek Experimental Watershed, D2P successfully resolved 86% of the ponds at a DEM resolution of 10 m. Topographic conditioning was achieved with minimum impact as D2P reduced the number of modified cells from the original DEM by 51% compared to a conventional algorithm. Furthermore, hydrologic simulation using a D2P processed DEM resulted in a more robust characterization on surface water dynamics based on higher surface water storage as well as an attenuated and delayed peak streamflow.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1972

Bistatic-radar investigation

The purpose of the reported experiment was to determine the principal electromagnetic and structural properties of the lunar surface from the observation of command and service module (CSM) radio transmissions that were reflected from the lunar surface and received on earth. These transmissions emanate from the CSM communication systems at wavelengths of 13 cm (S-band) and 116 cm (very high frequency (VHF)). Lunar crustal properties such as dielectric constant, average slope and slope probability, density, small-scale surface roughness, and embedded rocks to a depth of 20 m may be determined. The results are proving to be most useful in understanding the processes that have produced and modified the crust and in distingushing between adjacent and subjacent geological units. The experimental observations are also of intrinsic interest in the study of electromagnetic scattering.

Howard, H. T.↗
NASA NTRS1990

A preliminary estimate of geoid-induced variations in repeat orbit satellite altimeter observations

Altimeter satellites are often maintained in a repeating orbit to facilitate the separation of sea-height variations from the geoid. However, atmospheric drag and solar radiation pressure cause a satellite orbit to drift. For Geosat this drift causes the ground track to vary by + or - 1 km about the nominal repeat path. This misalignment leads to an error in the estimates of sea surface height variations because of the local slope in the geoid. This error has been estimated globally for the Geosat Exact Repeat Mission using a mean sea surface constructed from Geos 3 and Seasat altimeter data. Over most of the ocean the geoid gradient is small, and the repeat-track misalignment leads to errors of only 1 to 2 cm. However, in the vicinity of trenches, continental shelves, islands, and seamounts, errors can exceed 20 cm. The estimated error is compared with direct estimates from Geosat altimetry, and a strong correlation is found in the vicinity of the Tonga and Aleutian trenches. This correlation increases as the orbit error is reduced because of the increased signal-to-noise ratio.

Brenner, Anita C.↗
NASA NTRS1971

Lunar surface engineering properties experiment definition. Volume 2: Mechanics of rolling sphere-soil slope interaction

The soil deformation mode under the action of a rolling sphere (boulder) was determined, and a theory based on actual soil failure mechanism was developed which provides a remote reconnaissance technique for study of soil conditions using boulder track observations. The failure mechanism was investigated by using models and by testing an instrumented spherical wheel. The wheel was specifically designed to measure contact pressure, but it also provided information on the failure mechanism. Further tests included rolling some 200 spheres down sand slopes. Films were taken of the rolling spheres, and the tracks were measured. Implications of the results and reevaluation of the lunar boulder tracks are discussed.

Hovland, H. J.↗
DOE OSTI2022

Where does the dust deposited over the Sierra Nevada snow come from?

Abstract. Mineral dust contributes up to one-half of surface aerosol loading in spring over the southwestern United States, posing an environmental challenge that threatens human health and the ecosystem. Using self-organizing map (SOM) analysis with dust deposition and flux data from WRF-Chem and Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2), we identify four typical dust transport patterns across the Sierra Nevada, associated with the mesoscale winds, Sierra barrier jet (SBJ), North Pacific High (NPH), and long-range cross-Pacific westerlies, respectively. We find that dust emitted from the Central Valley is persistently transported eastward, while dust from the Mojave Desert and Great Basin influences the Sierra Nevada during mesoscale transport occurring mostly in winter and early spring. Asian dust reaching the mountain range comes either from the west through straight isobars (cross-Pacific transport) or from the north in the presence of the NPH. Extensive dust depositions are found on the west slope of the mountain, contributed by Central Valley emissions and cross-Pacific remote transport. In particular, the SBJ-related transport produces deposition through landfalling atmospheric rivers, whose frequency might increase in a warming climate.

Huang, Huilin (ORCID:0000000273286738)↗