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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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

Dependence of the spectral surface irradiance on aerosol properties and surface reflectivity

A reduction in global surface irradiance occurs with increasing aerosol loadings when the aerosols are absorbing. For scattering aerosols, a reduction is pronounced for isotropic scattering (characteristic of small particles) but reduction is not as significant for scattering with a high anisotropy of a large forward peak (characteristic of large particles). This distinction between isotropic and anisotropic scattering becomes small or null over highly reflecting terrain; and for reflectivities higher than 0.5 and solar elevation angles close to the zenith, the global irradiance can be slightly higher for isotropic scattering than in the case of an anisotropy of a forward peak. Under such conditions, which can be encountered in reflective infrared bands over dense vegetation or over sandy deserts (close to noon, in low latitudes) the surface irradiance becomes nearly independent of the aerosol optical thickness.

Otterman, J.↗
NASA NTRS1974

Surface electrical properties experiment

The Surface Electrical Properties Experiment (SEP) was flown to the moon in December 1972 on Apollo 17 and used to explore a portion of the Taurus-Littrow region. SEP used a relatively new technique, termed radio frequency interferometry (RFI). Electromagnetic waves were radiated from two orthogonal, horizontal electric dipole antennas on the surface of the moon at frequencies of 1, 2, 4, 8, 16, and 32 Mhz. The field strength of the EM waves was measured as a function of distance with a receiver mounted on the Lunar Roving Vehicle and using three orthogonal, electrically small, loops. The interference pattern produced by the waves that travelled above the moon's surface and those that travelled below the surface was recorded on magnetic tape. The tape was returned to earth for analysis and interpretation. Several reprints, preprints, and an initial draft of the first publication of the SEP results are included. These documents provide a rather complete account of the details of the theory of the RFI technique, of the terrestrial tests of the technique, and of the present state of our interpretation of the Apollo 17 data.

Simmons, G.↗
NASA NTRS1973

Surface electrical properties experiment

The surface electrical properties (SEP) experiment was used to explore the subsurface material of the Apollo 17 landing site by means of electromagnetic radiation. The experiment was designed to detect electrical layering, discrete scattering bodies, and the possible presence of water. From the analysis of the data, it was expected that values of the electrical properties (dielectric constant and loss tangent) of lunar material in situ would be obtained. The basic principle of the SEP experiment is interferometry. This principle involves only the interference of two or more waves to produce an interference pattern. The inversion of the interference pattern in terms of the spatial distribution of the electrical properties is the basic aim of the experiment (fig. 15-1). The experiment is most easily understood in terms of a single dipole antenna for radiating electromagnetic energy and a loop receiver for measuring the magnitudes of the fields.

Simmons, G.↗
NASA NTRS1975

Effect of polymer properties and adherend surfaces on adhesion

The surface properties associated with good adhesive joints were evaluated in terms of application of adhesive bonding in aerospace technology. The physical and chemical nature was determined of Ti and Al adherend surfaces after various surface treatments, and the effects on fracture surfaces of high temperature aging, and variations in amide, anhydride, and solvent during polymer synthesis. The effects were characterized of (1) high temperature during shear strength testing, (2) fiber-reinforced composites as adherends, (3) acid/base nature of adherends, (4) aluminum powder adhesive filler, and (5) bonding pressure.

Dwight, D. W.↗
NASA NTRS1992

How well can regional fluxes be derived from smaller-scale estimates?

Regional surface fluxes are essential lower boundary conditions for large scale numerical weather and climate models and are the elements of global budgets of important trace gases. Surface properties affecting the exchange of heat, moisture, momentum and trace gases vary with length scales from one meter to hundreds of km. A classical difficulty is that fluxes have been measured directly only at points or along lines. The process of scaling up observations limited in space and/or time to represent larger areas was done by assigning properties to surface classes and combining estimated or calculated fluxes using an area weighted average. It is not clear that a simple area weighted average is sufficient to produce the large scale from the small scale, chiefly due to the effect of internal boundary layers, nor is it known how important the uncertainty is to large scale model outcomes. Simultaneous aircraft and tower data obtained in the relatively simple terrain of the western Alaska tundra were used to determine the extent to which surface type variation can be related to fluxes of heat, moisture, and other properties. Surface type was classified as lake or land with aircraft borne infrared thermometer, and flight level heat and moisture fluxes were related to surface type. The magnitude and variety of sampling errors inherent in eddy correlation flux estimation place limits on how well any flux can be known even in simple geometries.

Moore, Kathleen E.↗
NASA NTRS1993

How well can regional fluxes be derived from smaller-scale estimates?

Regional surface fluxes are essential lower boundary conditions for large scale numerical weather and climate models and are the elements of global budgets of important trace gases. Surface properties affecting the exchange of heat, moisture, momentum and trace gases vary with length scales from one meter to hundreds of km. A classical difficulty is that fluxes have been measured directly only at points or along lines. The process of scaling up observations limited in space and/or time to represent larger areas was done by assigning properties to surface classes and combining estimated or calculated fluxes using an area weighted average. It is not clear that a simple area weighted average is sufficient to produce the large scale from the small scale, chiefly due to the effect of internal boundary layers, nor is it known how important the uncertainty is to large scale model outcomes. Simultaneous aircraft and tower data obtained in the relatively simple terrain of the western Alaska tundra were used to determine the extent to which surface type variation can be related to fluxes of heat, moisture, and other properties. Surface type was classified as lake or land with aircraft borne infrared thermometer, and flight level heat and moisture fluxes were related to surface type. The magnitude and variety of sampling errors inherent in eddy correlation flux estimation place limits on how well any flux can be known even in simple geometries.

Moore, Kathleen E.↗
NASA NTRS1984

Contactless Measurement of Physical Properties

Surface tension and other properties determined from measurement of resonant frequency. Surface tension and other physical properties of molten and liquid samples excited at resonance measured by observing photographic or TV image and noting resonant frequency and rate of change. Technique used in normal gravity and low gravity in either vacuum or gaseous environment, where sample is positioned by electrostatic, acoustic, or magnetic forces.

Elleman, D. D.↗
NASA NTRS2003

Using Remote Sensing Platforms to Estimate Near-Surface Soil Properties

Evaluation of near-surface soil properties via remote sensing (RS) could facilitate soil survey mapping, erosion prediction, fertilization regimes, and allocation of agrochemicals. The objective of this study was to evaluate the relationship between soil spectral signature and near surface soil properties in conventionally managed row crop systems. High resolution RS data were acquired over bare fields in the Coastal Plain, Appalachian Plateau, and Ridge and Valley provinces of Alabama using the Airborne Terrestrial Applications Sensor (ATLAS) multispectral scanner. Soils ranged from sandy Kandiudults to fine textured Rhodudults. Surface soil samples (0-1 cm) were collected from 163 sampling points for soil water content, soil organic carbon (SOC), particle size distribution (PSD), and citrate dithionite extractable iron (Fed) content. Surface roughness, soil water content, and crusting were also measured at sampling. Results showed RS data acquired from lands with less than 4 % surface soil water content best approximated near-surface soil properties at the Coastal Plain site where loamy sand textured surfaces were predominant. Utilizing a combination of band ratios in stepwise regression, Fed (r2 = 0.61), SOC (r2 = 0.36), sand (r2 = 0.52), and clay (r2 = 0.76) were related to RS data at the Coastal Plain site. In contrast, the more clayey Ridge and Valley soils had r-squares of 0.50, 0.36, 0.17, and 0.57. for Fed, SOC, sand and clay, respectively. Use of estimated eEmissivity did not generally improve estimates of near-surface soil attributes.

Sullivan, D. G.↗
NASA NTRS1973

The Apollo 17 Surface Electrical Properties Experiment antenna performance.

The electrical properties of the lunar surface in the area of the Apollo 17 landing site were recently studied by the use of electromagnetic sounding techniques. The Apollo 17 Surface Electrical Properties Experiment was different from most other electromagnetic investigations of the lunar surface in that both the transmitting and receiving equipment was located directly on the lunar surface. The use of such inplace measurements of the electrical properties of the lunar surface is significant in that the exact structure and density of the soil contributes largely to the total electrical model of the moon. This paper will be concerned with a discussion of the transmitter antenna design problems for the Surface Electrical Properties Experiment as well as what is indicated by the returned lunar data about the transmitter antenna performance during the Apollo 17 mission.

Cubley, H. D.↗
NASA NTRS2005

Using Remote Sensing Data to Evaluate Surface Soil Properties in Alabama Ultisols

Evaluation of surface soil properties via remote sensing could facilitate soil survey mapping, erosion prediction and allocation of agrochemicals for precision management. The objective of this study was to evaluate the relationship between soil spectral signature and surface soil properties in conventionally managed row crop systems. High-resolution RS data were acquired over bare fields in the Coastal Plain, Appalachian Plateau, and Ridge and Valley provinces of Alabama using the Airborne Terrestrial Applications Sensor multispectral scanner. Soils ranged from sandy Kandiudults to fine textured Rhodudults. Surface soil samples (0-1 cm) were collected from 163 sampling points for soil organic carbon, particle size distribution, and citrate dithionite extractable iron content. Surface roughness, soil water content, and crusting were also measured during sampling. Two methods of analysis were evaluated: 1) multiple linear regression using common spectral band ratios, and 2) partial least squares regression. Our data show that thermal infrared spectra are highly, linearly related to soil organic carbon, sand and clay content. Soil organic carbon content was the most difficult to quantify in these highly weathered systems, where soil organic carbon was generally less than 1.2%. Estimates of sand and clay content were best using partial least squares regression at the Valley site, explaining 42-59% of the variability. In the Coastal Plain, sandy surfaces prone to crusting limited estimates of sand and clay content via partial least squares and regression with common band ratios. Estimates of iron oxide content were a function of mineralogy and best accomplished using specific band ratios, with regression explaining 36-65% of the variability at the Valley and Coastal Plain sites, respectively.

Sullivan, Dana G.↗
NASA NTRSDate not supplied

Forward and Inverse Models for Satellite Remote Sensors using Principal Component Analysis

Satellite remote sensors such as AIRS on Aqua, CrIS on S-NPP, NOAA20 and JPSS-2, IASI on Metop A, B, and C make millions of observations each day with thousands of spectral channels for each observation; this poses challenges for efficiently inversion of the inherently large dataset as needed to retrieve atmospheric and surface properties. This presentation will illustrate the use of Principal Component Analysis (PCA) to speed up radiative transfer forward model calculations and to stabilize the inversion algorithms. A Principal Component-based radiative transfer model (PCRTM) developed at NASA Langley Research Center can simulate top of atmosphere (TOA) radiance or reflectance spectra from 50 cm-1 to 50000 cm-1 (200 m to 0.20 m quickly and accurately. PCRTM demonstrated very high accuracy relative to reference line-by-line radiative transfer models and it saves orders of magnitude computational time. Examples of the PCRTM model developed for hyperspectral sensors such as AIRS, CrIS, IASI, NAST-I, SHIS, CPF, TEMPO, SBG, OMI, and SCIAMACHY will be presented. In addition to using the PCRTM as forward model, the NASA Langley developed inversion algorithm also uses PCA to compress the state vector into a compressed dimension to speed up and stabilize the inversion process. Examples of retrieved atmospheric temperature, water vapor, CO2, CO, CH4, N2O, and O3 profiles, cloud properties (optical depth, size, phase, and height), and surface properties (surface emissivity spectra and skin temperatures) will be presented. This algorithm is being transitioned to the NASA Sounder SIPS and NASA's Goddard Earth Sciences Data and Information Services Center (GES DISC).

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