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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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NASA NTRS2021

Comparison of soil dielectric mixing models for Soil Moisture Retrieval using SMAP Brightness Temperature over croplands in India

The accurate estimation of soil moisture (SM) using microwave remote sensing depends mostly on careful selection of retrieval parameters among which the soil dielectric mixing model is the important one. These models are often categorized into empirical, semi-empirical or volumetric based on their methodologies and input data requirements. To study in detail, the comparative performance of four dielectric mixing models -- Wang & Schmugge model, Hallikainen model, Dobson model and Mironov model were used with Soil Moisture Active Passive (SMAP) L-band brightness temperature and Single Channel Algorithm for SM retrieval over agricultural landscapes in India. The highest performance statistics combination in terms of Root Mean Square Error (RMSE), correlation coefficient (R^(2)) and percentage bias (PBIAS) against the concurrent in-situ SM measurements were calculated at the selected validation sites. The overall results indicate that the best performance was given by the Mironov model (RMSE = 0.07 cu. m/cu. m), followed by Wang & Schmugge model (RMSE = 0.08 cu. m3/cu. m), Hallikainen model (RMSE = 0.09 cu. m/cu. m), Dobson model (RMSE = 0.10 cu. m/cu. m) and original SMAP radiometer SM (RMSE = 0.12 cu. m/cu. m). Findings of this study provides important insights into application and performance of dielectric mixing models in mapping surface SM variations. This study also underlines the pivotal role of local conditions for SM retrieval which should be carefully included in the algorithms.

Swati Suman↗
NASA NTRS2018

Soil Moisture Active Passive (SMAP) Mission Level 4 Surface and Root Zone Soil Moisture (L4_SM) Product Specification Document

This is the Product Specification Document (PSD) for Level 4 Surface and Root Zone Soil Moisture (L4_SM) data for the Science Data System (SDS) of the Soil Moisture Active Passive (SMAP) project. The L4_SM data product provides estimates of land surface conditions based on the assimilation of SMAP observations into a customized version of the NASA Goddard Earth Observing System, Version 5 (GEOS-5) land data assimilation system (LDAS). This document applies to any standard L4_SM data product generated by the SMAP Project.

Soil Moisture↗
NASA NTRS1969

Desert soil collection at the JPL soil science laboratory

Collection contains desert soils and other geologic materials collected from sites in the United States and foreign countries. Soils are useful for test purposes in research related to extraterrestrial life detection, sampling, harsh environmental studies, and determining suitable areas for training astronauts for lunar exploration.

Blank, G. B.↗
NASA NTRS1974

Utilizing ERTS imagery to detect plant diseases and nutrient deficiencies, soil types and soil moisture levels

The author has identified the following significant results. ERTS-1 imagery may be used to delineate soil associations. It does have the capacity to divide soils into groups such that their land use and management would be similar. It offers definite potential for making grass flood-plain, wetland, river shoreline, and land use change surveys. Production of volume strata and forest type from the two usable bands of ERTS-1 imagery were of questionable value. No imagery was received for evaluation during the time of year when maine dwarf mosaic virus and southern corn leaf blight were active.

Parks, W. L.↗
NASA NTRS1974

Surface history of lunar soil and soil columns

Measurements of cosmic ray track densities are presented for soil samples from Apollo 15, 16, and 17. Median track densities are used to infer total effective exposure times within about 15 cm of the lunar surface. Minimum track densities are used to derive the time of the last impact-produced rearrangement of soil grains. For samples from near various craters ages are derived of 40 m.y. for St. George, 6 (plus or minus 3) m.y. for S. Ray, 25 to 90 m.y. for Plum, and 20 to 35 m.y. for Shorty. The material of 15003, the Apollo 15 deep core at depths of 120 to 160 cm, is inferred to have been deposited at an average rate greather than or equal to 0.35 cm/m.y. The Apollo 16 core at 41 to 47 cm depths, 60007, appears to be well mixed and was covered up by deposition at greater than 0.3 cm/m.y. for the next few m.y. after its deposition.

Fleischer, R. L.↗
NASA NTRS1978

Soils from Mare Crisium - Agglutinitic glass chemistry and soil development

Agglutinates were studied in 29 polished thin sections of grain mounts from various size fractions of six Luna 24 soil horizons. Three populations of agglutinitic glass compositions were found: a high-MgO, high-FeO group identified as a coarse-grained basaltic component; a low-MgO, low-FeO group from a highland source; and a low-MgO, high-FeO group probably from the subophitic basalt component. The presence of a significant amount of admixed highland component probably accounts for an enrichment in plagioclase and a depletion in ferromagnesian elements displayed by the agglutinitic glass compositions relative to the bulk soil.

Hu, H.-N.↗
NASA NTRS1984

Utilization of active microwave roughness measurements to improve passive microwave soil moisture estimates over bare soils

Multisensor aircraft data were used to establish the potential of the active microwave sensor response to be used to compensate for roughness in the passive microwave sensor's response to soil moisture. Only bare fields were used. It is found that the L-band radiometer's capability to estimate soil moisture significantly improves when surface roughness is accounted for with the scatterometers.

Theis, S. W.↗
NASA NTRS1983

Potential for monitoring soil erosion features and soil erosion modeling components from remotely sensed data

Accurate estimates of soil erosion and its effects on soil productivity are essential in agricultural decision making and planning from the field scale to the national level. Erosion models have been primarily developed for designing erosion control systems, predicting sediment yield for reservoir design, predicting sediment transport, and simulating water quality. New models proposed are more comprehensive in that the necessary components (hydrology, erosion-sedimentation, nutrient cycling, tillage, etc.) are linked in a model appropriate for studying the erosion-productivity problem. Recent developments in remote sensing systems, such as Landsat Thematic Mapper, Shuttle Imaging Radar (SIR-B), etc., can contribute significantly to the future development and operational use of these models.

Langran, K. J.↗
NASA NTRS1983

Spectral reflectance of surface soils: Relationships with some soil properties

Using a published atlas of reflectance curves and physicochemical properties of soils, a statistical analysis was carried out. Reflectance bands which correspond to five of the wavebands used by NASA's Thematic Mapper were examined for relationships to specific soil properties. The properties considered in this study include: Sand Content, Silt Content, Clay Content, Organic Matter Content, Cation Exchange Capacity, Iron Oxide Content and Moisture Content. Regression of these seven properties on the mean values of five TM bands produced results that indicate that the predictability of the properties can be increased by stratifying the data. The data was stratified by parent material, taxonomic order, temperature zone, moisture zone and climate (combined temperature and moisture). The best results were obtained when the sample was examined by climatic classes. The middle Infra-red bands, 5 and 7, as well as the visible bands, 2 and 3, are significant in the model. The near Infra-red band, band 4, is almost as useful and should be included in any studies. General linear modeling procedures examined relationships of the seven properties with certain wavebands in the stratified samples.

Kiesewetter, C. H.↗
NASA NTRS1986

Utilization of active microwave roughness measurements to improve passive microwave soil moisture estimates over bare soils

Multisensor aircraft data were used to establish the potential of the active microwave sensor response to be used to compensate for roughness in the passive microwave sensor's response to soil moisture. Only bare fields were used. It is found that the L-band radiometer's capability to estimate soil moisture significantly improves when surface roughness is accounted for with the scatterometers.

Theis, S. W.↗
NASA NTRS1987

Significance of foundation-soil separation in dynamic soil-structure interaction

THe dynamic response of flexible surface strip-foundations allowed to uplift is numerically obtained for externally applied forces of a transient time variation. The soil medium is represented by an isotropic, homogeneous and linear half-space. The soil is treated by a time domain boundary element method, while the flexible foundation is treated by the finite element method. It was concluded that intermediate relative stiffness leads to moderate deformations when uplift is permitted. Very flexible footings produce higher deformations in unilateral contact compared to bilateral contact, and thus should be considered in their design. Unilateral contact does not significantly increase deformations for stiff footings subjected to concentrated central loading. However, relatively large deformation differences occur when the loading is eccentric, necessitating consideration of uplift in their design.

Spyrakos, Constantine C.↗
NASA NTRS2005

Converting Soil Moisture Observations to Effective Values for Improved Validation of Remotely Sensed Soil Moisture

We compare soil moisture retrieved with an inverse algorithm with observations of mean moisture in the 0-6 cm soil layer. A significant discrepancy is noted between the retrieved and observed moisture. Using emitting depth functions as weighting functions to convert the observed mean moisture to observed effective moisture removes nearly one-half of the discrepancy noted. This result has important implications in remote sensing validation studies.

Laymon, Charles A.↗
NASA NTRS2009

A Model of Thermal Conductivity for Planetary Soils: 1. Theory for Unconsolidated Soils

We present a model of heat conduction for mono-sized spherical particulate media under stagnant gases based on the kinetic theory of gases, numerical modeling of Fourier s law of heat conduction, theoretical constraints on the gas thermal conductivity at various Knudsen regimes, and laboratory measurements. Incorporating the effect of the temperature allows for the derivation of the pore-filling gas conductivity and bulk thermal conductivity of samples using additional parameters (pressure, gas composition, grain size, and porosity). The radiative and solid-to-solid conductivities are also accounted for. Our thermal model reproduces the well-established bulk thermal conductivity dependency of a sample with the grain size and pressure and also confirms laboratory measurements finding that higher porosities generally lead to lower conductivities. It predicts the existence of the plateau conductivity at high pressure, where the bulk conductivity does not depend on the grain size. The good agreement between the model predictions and published laboratory measurements under a variety of pressures, temperatures, gas compositions, and grain sizes provides additional confidence in our results. On Venus, Earth, and Titan, the pressure and temperature combinations are too high to observe a soil thermal conductivity dependency on the grain size, but each planet has a unique thermal inertia due to their different surface temperatures. On Mars, the temperature and pressure combination is ideal to observe the soil thermal conductivity dependency on the average grain size. Thermal conductivity models that do not take the temperature and the pore-filling gas composition into account may yield significant errors.

Piqueux, S.↗