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Results for “soil structure”

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 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

A landscape view of biomass, LAI, and photosynthetic capacity for FIFE

Canopy properties in the tallgrass prairie are examined in terms of spatial and temporal variability to determine how the variability constrains the ecosystem-atmosphere exchange of H2O, CO2, and momentum. Canopy structure and photosynthetic capacity are examined by measuring soil properties, canopy biomass, and canopy nitrogen along continuous strips. Special attention is given to sites of maximum and minimum biomass where parameters such as leaf-area index (LAI), photosynthetic rate, chemistry, and structures for both burned and unburned areas. The LAI/biomass data and the canopy attributes show that soil properties are shaped by soil-forming and geomorphic processes. The variables that cause the greatest variation in LAI, canopy stratification, and photosynthetic capacity are found to be management (burning and/or grazing) and landscape position.

Kittel, T. G. F.↗
NASA NTRS1972

Fluorescent antibody detection of microorganisms in terrestrial environments

The fluorescent antibody technique and its use in direct microscopic examination of the soil is discussed. Feasibility analyses were made to determine if the method could be used to simultaneously observe and recognize microorganisms in the soil. Some data indicate this may be possible. Data are also given on two related problems involving the interaction of soil microorganisms with plant roots to form symbiotic structures. One was concerned with the developmental ecology and biology of the root nodule of alder and the second was concerned with the ectotrophic mycorrhizal structure on forest trees, especially pines. In both, the fluorescent antibody detection of the microbial symbiont both as a free living form in soil, and as a root inhabiting form in the higher plant was emphasized. A third aspect of the research involved the detection of autotrophic ammonia oxidizing microorganisms in soil.

Schmidt, E. L.↗
NASA NTRS1971

Foldable patterns form construction blocks

Building blocks with interlocking tabs can be constructed from flat sheets of material using minimum of tools and equipment. Blocks can be used for storing and shipping supplies to remote areas, then filled with soil and stacked to form inhabitable structures which can be dismantled and reused.

Huber, W. C.↗
NASA NTRS1980

Active microwave remote sensing research program plan. Recommendations of the Earth Resources Synthetic Aperture Radar Task Force

A research program plan developed by the Office of Space and Terrestrial Applications to provide guidelines for a concentrated effort to improve the understanding of the measurement capabilities of active microwave imaging sensors, and to define the role of such sensors in future Earth observations programs is outlined. The focus of the planned activities is on renewable and non-renewable resources. Five general application areas are addressed: (1) vegetation canopies, (2) surface water, (3) surface morphology, (4) rocks and soils, and (5) man-made structures. Research tasks are described which, when accomplished, will clearly establish the measurement capabilities in each area, and provide the theoretical and empirical results needed to specify and justify satellite systems using imaging radar sensors for global observations.

Source record↗
NASA NTRS1984

Evaluation of LANDSAT-D Thematic Mapper performance as applied to hydrocarbon exploration

Work with digital data of Oklahoma, Colorado, Wyoming, Utah and California demonstrate that the increased spectral refinement and spatial resolution of TM over MSS data greatly increase the value of the data to petroleum exploration in roles ranging from logistic planning to direct detection of phenomena related to microseepage of hydrocarbons. The value of the spatial content versus the spectral content of the data increases as soil and vegetation cover increase. The structural detail visible in the imagery can contribute to exploration at the prospect level. Examination of the variance/covariance matrix suggests that a combination of bands 1, 4, and 5 displays the most information for most areas.

Dykstra, J. D.↗
NASA NTRS1992

Comparison of Goldstone and Magellan radar data in the equatorial plains of Venus

Goldstone radar observations of the equatorial plains of Venus provide complementary information to that obtained by Magellan. Different radar scattering mechanisms dominate each system, leading to sampling of different surface properties. Comparison of image data and derived parameters indicate that: (1) relatively high dielectric constants on impact-related parabolic features are detected in Goldstone backscatter, Magellan reflectivity, and Magellan emissivity data; the dielectric effects are overwhelmed by roughness-related signatures in Magellan synthetic aperture radar (SAR) data; (2) lava flows in Navka Planitia show dielectric variations both among and within flows; higher dielectric constants on the perimeter of some flows may by due to a decrease in vesicularity; (3) some volcanic domes are relatively smooth at the wavelength scale and probably consist of low-density deposits; (4) comparisons of Magellan SAR data with rough surface scattering models and SAR data of terrestrial surfaces indicate that the roughness characteristics of the equatorial plains surfaces are comparable to modified terrestrial lava flows; and (5) scattering properties of an equatorial 'ridge belt' structure suggest highly weathered or soil-dominated surfaces.

Plaut, Jeffrey J.↗
NASA NTRS1996

The Cause of the Hot Spot in Vegetation Canopies and Soils: Shadow-Hiding Versus Coherent Backscatter

Two different mechanisms, shadow-hiding and coherent backscatter, can cause a hot spot, or opposition effect, in the bidirectional reflectance of vegetation and soils. Because the two mechanisms sample different properties, it is important to know which one is primarily responsible in a given medium. This question can be answered by measuring the bidirectional reflectance in circularly polarized light. If the results of the limited experiments reported here can be extrapolated to a wider range of materials, it appears that the primary cause of the hot spot in most vegetation canopies and in moist, clumpy soils is shadow-hiding. However, in vegetation with large numbers of wavelength-sized structures, such as mosses, and in dry, fine-grained soils, the hot spot is dominated by coherent backscatter.

Hapke, Bruce↗
NASA NTRS2013

Microwave Sinterator Freeform Additive Construction System (MS-FACS)

The harmful properties of lunar dust, such as small size, glass composition, abnormal surface area, and coatings of imbedded nanophase iron, lead to a unique coupling of the dust with microwave radiation. This coupling can be exploited for rapid sintering of lunar soil for use as a construction material that can be formed to take on an infinite number of shapes and sizes. This work describes a system concept for building structures on the lunar surface using lunar regolith (soil). This system uses the ATHLETE (All-Terrain Hex- Limbed Extra-Terrestrial Explorer) mobility system as a positioning system with a microwave print head (similar to that of a smaller-scale 3D printer). A processing system delivers the lunar regolith to the microwave print head, where the microwave print head/chamber lays down a layer of melted regolith. An arm on the ATHLETE system positions the layer depending on the desired structure.

Howe, Alan S.↗
NASA NTRS1995

Low-temperature and low atmospheric pressure infrared reflectance spectroscopy of Mars soil analog materials

Infrared reflectance spectra of carefully selected Mars soil analog materials have been measured under low atmospheric pressures and temperatures. Chemically altered montmorillonites containing ferrihydrite and hydrated ferric sulfate complexes are examined, as well as synthetic ferrihydrate and a palagonitic soil from Haleakala, Maui. Reflectance spectra of these analog materials exhibit subtle visible to near-infrared features, which are indicative of nanophase ferric oxides or oxyhydroxides and are similar to features observed in the spectra of the bright regions of Mars. Infrared reflectance spectra of these analogs include hydration features due to structural OH, bound H2O and adsorbed H2O. The spectal character of these hydration features is highly dependent on the sample environment and on the nature of the H2O/OH in the analogs. The behavior of the hydration features near 1.9 micrometers, 2.2 micrometers, 2.7 micrometers, 3 micrometers, and 6 micrometers are reported here in spetra measured under Marslike atmospheric environment. In spectra of these analogs measured under dry Earth atmospheric conditions the 1.9-micrometer band depth is 8-17%; this band is much stonger under moist conditions. Under Marslike atmospheric conditions the 1.9-micrometer feature is broad and barely discernible (1-3% band depth) in spectra of the ferrihydrite and palagonitic soil samples. In comparable spectra of the ferric sulfate-bearing montmorillonite the 1.9-micrometer feature is also broad, but stronger (6% band depth). In the low atmospheric pressure and temperature spectra of the ferrihydrite-bearing montmorillonite this feature is sharper than the other analogs and relatively stronger (6% band depth). Although the intensity of the 3- micrometer band is weaker in spectra of each of the analogs when measured under Marslike conditions, the 3-micromter band remains a dominant feature and is especially broad in spectra of the ferrihydrite and palagonitic soil. The structural OH features observed in these materials at 2.2-2.3 micrometers and 2.27 micrometers remain largely unaffected by the environmental conditions. A shift in the Christiansen feature towards shorter wavelengths has also been observed with decreasing atmospheric pressure and temperature in the midinfrared spectra of these samples.

Bishop, Janice L.↗
NASA NTRS1995

Low-temperature and low atmospheric pressure infrared reflectance spectroscopy of Mars soil analog materials

Infrared reflectance spectra of carefully selected Mars soil analog materials have been measured under low atmospheric pressures and temperatures. Chemically altered montmorillonites containing ferrihydrite and hydrated ferric sulfate complexes are examined, as well as synthetic ferrihydrite and a palagonitic soil from Haleakala, Maui. Reflectance spectra of these analog materials exhibit subtle visible to near-infrared features, which are indicative of nanophase ferric oxides or oxyhydroxides and are similar to features observed in the spectra of the bright regions of Mars. Infrared reflectance spectra of these analogs include hydration features due to structural OH, bound H2O, and adsorbed H2O. The spectral character of these hydration features is highly dependent on the sample environment and on the nature of the H2O/OH in the analogs. The behavior of the hydration features near 1.9 micron, 2.2 micron, 2.7 micron, 3 micron, and 6 microns are reported here in spectra measured under a Marslike atmospheric environment. In spectra of these analogs measured under dry Earth atmospheric conditions the 1.9-micron band depth is 8-17%; this band is much stronger under moist conditions. Under Marslike atmospheric conditions the 1.9-micron feature is broad and barely discernible (1-3% band depth) in spectra of the ferrihydrite and palagonitic soil samples. In comparable spectra of the ferric sulfate-bearing montmorillonite the 1.9-micron feature is also broad, but stronger (6% band depth). In the low atmospheric pressure and temperature spectra of the ferrihydrite-bearing montmorillonite this feature is sharper than the other analogs and relatively stronger (6% band depth). Although the intensity of the 3-micron band is weaker in spectra of each of the analogs when measured under Marslike conditions, the 3-micron band remains a dominant feature and is especially broad in spectra of the ferrihydrite and palagonitic soil. The structural OH features observed in these materials at 2.2-2.3 micron and 2.75 microns remain largely unaffected by the environmental conditions. A shift in the Christiansen feature towards shorter wavelengths has also been observed with decreasing atmospheric pressure and temperature in the midinfrared spectra of these samples.

Bishop, Janice L.↗
NASA NTRS1979

Space construction engineering - A new career field

Opportunities for engineers in the design and construction of future large space structures are outlined. Possible space structures for the 1980's include a large mirror to reflect sunlight to earth for night lighting, an antenna for a personal communications system, a deep space communications relay system and a large passive radiometer to measure soil moisture. Considerations in the design of such structures include the lack of gravity, allowing structures to be built with much less supporting weight, the cost of transportation to orbit, leading to the use of aluminum or composite materials stored on reels and attached to a beam builder, and the required surface accuracy in the presence of thermal stresses. Construction factors to consider include the use of astronauts and remote manipulators in assembly, both of which have been demonstrated to be feasible.

Hagler, T.↗
NASA NTRS2021

Reflectivity, Emissivity, and Brightness from Multilayered Soil with Linearly Varying Permittivity at P- and L- bands

Passive sensing of root zone soil moisture is theoretically investigated using P and L band frequencies. The soil is considered to be a stratified medium. The reflectivity from the soil surface is found by considering the soil to be composed of a finely layered structure with layer widths that are small compared to a wavelength. A well-known transmission line algorithm is then used to compute the reflectivity at the surface. Emissivity is obtained as (1 – reflectivity). It assumed that the soil is at a constant temperature of 300o K when determining the brightness temperature. A soil moisture profile consisting of two homogeneous layers separated by a layer of linearly varying soil moisture is investigated. The study is made at an incident angle of 40O for horizontal polarization at 0.8 and 1.4 GHz. Two variations of the basic profile are considered: a transition from a layer of lesser moisture to a layer of greater moisture and the opposite. In both cases the P band signal shows greater penetration than the L band case. There is greater penetration in the transition to drier soils. In both cases the L band signals show sensitivity to only the upper surface of the soil as expected.

Ming Li↗
NASA NTRS1982

Accomplishments of the NASA Johnson Space Center portion of the soil moisture project in fiscal year 1981

The NASA/JSC ground scatterometer system was used in a row structure and row direction effects experiment to understand these effects on radar remote sensing of soil moisture. Also, a modification of the scatterometer system was begun and is continuing, to allow cross-polarization experiments to be conducted in fiscal years 1982 and 1983. Preprocessing of the 1978 agricultural soil moisture experiment (ASME) data was completed. Preparations for analysis of the ASME data is fiscal year 1982 were completed. A radar image simulation procedure developed by the University of Kansas is being improved. Profile soil moisture model outputs were compared quantitatively for the same soil and climate conditions. A new model was developed and tested to predict the soil moisture characteristic (water tension versus volumetric soil moisture content) from particle-size distribution and bulk density data. Relationships between surface-zone soil moisture, surface flux, and subsurface moisture conditions are being studied as well as the ways in which measured soil moisture (as obtained from remote sensing) can be used for agricultural applications.

Paris, J. F.↗
NASA NTRS1984

Development and evaluation of techniques for using combined microwave and optical image data for vegetation studies

Techniques for using combined image data from the Shuttle Imaging Radar (SIR-B) and the LANDSAT Thematic Mapper (TM) or Multispectral Scanner (MSS) for studies of irrigated crops, and boreal and deciduous forests are developed and evaluated. The effects of the structure and composition of crop canopies and soil surfaces on multiangle L-band HH (Horizontal polarization for transmission and reception) backscattering and on optical reflectance (in TM or MSS bands viewed at the nadir) are investigated. The relative accuracy of digital, calibrated SIR-B image data and LANDSAT TM or MSS image data is evaluated. Textural information extraction-techniques are developed for radar and optical image analysis.

Paris, J. F.↗
NASA NTRSDate not supplied

Playing with DIRT: Building the Framework for a Comprehensive In-Situ Soil Materials Testing Database

Long-term, sustainable planetary exploration will require the ability to "live off the land," relying on In-Situ Resource Utilization (ISRU) and In-Situ Construction as core capabilities. Reduction of both risk and launch mass for lunar construction will require evaluating and comparing regolith materials for use as feedstocks suitable for in-situ beneficiation and fabrication of building components. These material assessment capabilities will inform lunar infrastructure design decisions, with co-benefits for terrestrial construction using in-situ materials. Current planetary construction technology development relies on lunar mapping and orbital data, Apollo-era sample analyses, current simulant inventories, and tests conducted using analog site soils. Requirements for lunar infrastructure design decisions and construction systems will be determined based on specific environmental conditions, mission architectures, and the materials available within traverse range of lunar feedstock processing depots. Critical for success is the capability to identify, evaluate and make effective use of a wide range of materials as they are found in-situ on the lunar surface. This paper discusses the development of a digital repository for data on soil and regolith properties, beginning with their structural performance in both cementitious and non-cementitious building material formulations. The Database for In-situ Resource Testing (DIRT) compiles a catalog of raw materials, additives, and formulations, with notations pertaining to material sources and preparation techniques entered via a web-based user interface. Design of consistent data schemas for site-sourced materials evaluation will facilitate linkage with relevant terrestrial and planetary materials databases while enabling guided data input via templates for participation by broader groups of collaborators. Results of these analyses are compiled in a centralized repository to generate insights applicable for regolith resources and landing sites yet to be precisely defined. Collection of thorough records of material characteristics, applications and performance will support innovative construction solutions not only for space infrastructure but for sustainable, resilient design in the terrestrial built environment.

Sarah Joey Seitz↗
NASA NTRSDate not supplied

Assimilation of Soil Moisture Observations Over Land Improves Analysis and Prediction of Tropical Cyclone Idai

Soil moisture conditions can impact the circulation and structure of a tropical cyclone (TC) when part or all of the circulation is over land. Dry land surface conditions may lead to faster dissipation of a TC over land, whereas very wet conditions may lead to a prolonged maintenance of its intensity. While this relationship is relatively well understood in theory, applications of these findings in the context of numerical weather prediction (NWP) have been limited. Here we present a case study that explores the potential of improving TC predictions through an improved soil moisture initialization in an NWP framework. Specifically, we examine the impact of assimilating observations from the NASA Soil Moisture Active Passive (SMAP) mission into the NASA Goddard Earth Observing System (GEOS) global weather model on the prediction of South-West Indian Ocean TC Idai (2019). SMAP provides accurate L-band (1.4 GHz) brightness temperatures (Tb) observations that are sensitive to soil moisture globally and at high revisit times of 2-3 days. It has previously been shown that the assimilation of SMAP Tbs significantly improves modeled land surface states. Here we evaluate: (i) forecasts initialized from an analysis that is comparable to the GEOS operational analysis (without SMAP Tb assimilation) and (ii) forecasts initialized from an analysis that additionally assimilates SMAP Tb observations. We find that in the analysis with SMAP assimilation, the TC has a better-defined, more aligned vertical structure over land relative to the control run; moreover, the analyzed TC size, as measured by the wind speed radius, better matches the observed TC size. We further find significant reductions in the forecast intensity error and the forecast along-track error, measured against observations. The largest error reductions occur at lead times of 36 to 72 hours, suggesting that the land with its longer memory gains in importance as a source of predictability at this timescale. An investigation of the underlying mechanisms leading to the skill improvements from SMAP data assimilation revealed that the assimilation of SMAP leads to wetter soil moisture conditions and an increased latent heat flux in the SMAP analysis, which results in a TC with higher column-integrated total moisture content and total energy compared to the control analysis.

Jana Kolassa↗