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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 73 records · Page 4
All sourcesNASA NTRSDOE OSTI
NASA NTRS1969

Passive remote sensing at microwave wavelength

The ways in which radio signals are affected by meteorological parameters are described, as are methods for interpreting the signals, the state-of-the-art in instrumentation, the current state of development of the field, and some problems and prospects for the future. It is shown that the temperature profile of the atmosphere, water vapor and ozone distribution, cloud water content, and certain surface properties can be measured with sufficient accuracy to provide useful meteorological information.

Staelin, D. H.↗
NASA NTRS1979

Satellite passive remote sensing of off-shore pollutants, volume 2

Satellite detection and monitoring of off-shore dumped pollutants, other than oil, are discussed. Summaries of satellite sensor performance in three spectral bands (visible, infrared, and microwave) are presented. The bulk of the report gives all the calculations, trade-offs and limitations of the three sensor systems. It is asserted that the problem of pollution monitoring is not a sensor problem but a problem of mathematical modeling and data processing.

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NASA NTRS1980

Passive microwave sensing of coastal area waters

A technique to remotely measure sea-surface temperature and salinity was demonstrated during the 1970's with a dual-frequency microwave radiometer system developed at the NASA Langley Research Center. Accuracies in temperature of 1 C and 1 part per thousand in salinity were obtained using state-of-the-art radiometers. Several aircraft programs for the measurement of coastal area waters demonstrating the application of the microwave radiometer system are discussed. Improvements of the microwave radiometer system during the 1980's and the design and development of new radiometer systems at other frequencies are outlined and related to potential applications.

Kendall, B. M.↗
NASA NTRS1981

Passive microwave sensing of snow characteristics over land

Truck-mounted, airborne, and spaceborne systems with various radiometers ranging in wavelength from 0.8 to 21 cm were used to measure the brightness temperatures of snow-covered areas at test sites near Steamboat Springs and Walden, Colorado. The brightness temperature at a short wavelength (0.8 cm) was found to decrease more rapidly with increasing snow depth than the brightness temperature at a longer wavelength (6 cm). More scattering of the shorter-wavelength radiation by the snow crystals results in a lower brightness temperature. The longer-wavelength (6 cm) radiation penetrates through meters of dry snowpack and is useful for the assessment of the underlying ground conditions.

Chang, A. T. C.↗
NASA NTRS1980

Some adaptive filtering techniques applied to the passive remote sensing problem

A review is made of recursive statistical regression techniques incorporating past or past and future observations through smoothing and Kalman filtering, respectively; with results for the cases of the Tiros-N/MSU and Nimbus-6/Scams remote sensing satellite experiments. In response to the lack of a satisfactory model for the medium sounded, which is presently a major limitation on retrieval technique performance, a novel, global approach is proposed which casts the retrieval problem into the framework of adaptive filtering. A numerical implementation of such an adaptive system is presented, with a multilayer, semi-spectral general circulation model for the atmosphere being used to fine-tune the sensor as well as the dynamical equations of a Kalman filter. It is shown that the assimilation of radiometric data becomes a straightforward subproblem.

Toldalagi, P. M.↗
NASA NTRS1982

Tropospheric passive remote sensing: Introduction

Measurement needs regarding chemical and transport parameters were identified. Measurement of those gases involved in tropospheric photochemistry (O3, CO, CH4, NOx, HNO3, SO2, NH3, and CH3CCl3) and quantification of their sources and sinks, as well as a fundamental understanding of atmospheric chemical transformations were discussed. The photochemistry of OH and its role as a sink are summarized. The concentrations and lifetimes of the tropospheric gases were considered. Major concerns in tropospheric transport are the making of representative remote measurements of trace gases and aerosols and the dependence of these measurements on structural differences in the atmosphere.

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NASA NTRS1982

Technology thrusts for passive remote sensing. Sensing Technology Panel report

Technology thrusts for broadband spectrometry and gas filter radiometry development are identified. The development of 'smart' processing and cryogenics/cooling systems for all types of broadband spectrometers is advised. The use of large fixed gratings and the development of 1000-element arrays is recommended. Improvements suggested for interferometers are: the mitigation of background fluctuations; the development of multiaperature, multiband interferometers; and provision of in-flight alignment verification. Specifically recommended for gas filter radiometers are the development of gas filter cell technology, of liner and high dynamic range detectors, and of high uniform optical elements.

Source record↗
NASA NTRS1983

Passive microwave sensing of soil moisture content - The effects of soil bulk density and surface roughness

Microwave radiometric measurements over bare fields of different surface roughness were made at frequencies of 1.4 GHz, 5 GHz, and 10.7 GHz to study the frequency dependence, as well as the possible time variation, of surface roughness. An increase in surface roughness was found to increase the brightness temperature of soils and reduce the slope of regression between brightness temperature and soil moisture content. The frequency dependence of the surface roughness effect was relatively weak when compared with that of the vegetation effect. Radiometric time-series observations over a given field indicate that field surface roughness might gradually diminish with time, especially after a rainfall or irrigation. The variation of surface roughness increases the uncertainty of remote soil moisture estimates by microwave radiometry. Three years of radiometric measurements over a test site revealed a possible inconsistency in the soil bulk density determination, which is an important factor in the interpretation of radiometric data.

Wang, J. R.↗
NASA NTRS1982

Passive microwave sensing of soil moisture content: Soil bulk density and surface roughness

Microwave radiometric measurements over bare fields of different surface roughnesses were made at the frequencies of 1.4 GHz, 5 GHz, and 10.7 GHz to study the frequency dependence as well as the possible time variation of surface roughness. The presence of surface roughness was found to increase the brightness temperature of soils and reduce the slope of regression between brightness temperature and soil moisture content. The frequency dependence of the surface roughness effect was relatively weak when compared with that of the vegetation effect. Radiometric time series observation over a given field indicated that field surface roughness might gradually diminish with time, especially after a rainfall or irrigation. This time variation of surface roughness served to enhance the uncertainty in remote soil moisture estimate by microwave radiometry. Three years of radiometric measurements over a test site revealed a possible inconsistency in the soil bulk density determination, which turned out to be an important factor in the interpretation of radiometric data.

Wang, J. R.↗
NASA NTRS1983

Passive remote sensing of ocean optical propagation parameters

A method is described for producing a global data of ocean optical properties through the exploitation of optical remote sensing techniques. The diffuse attenuation, K, and the radiance reflectance factor R sub L, of the ocean surface waters can be derived from the radiance data provided by the Coastal Zone Color Scanner and compiled into a computer based atlas of these properties. While these remotely sensed values can only be directly related to the water properties in the first or upper attenuation length, extensive in water measurements have demonstrated that a useful correlation exists between the K that applies to the upper attenuation length, for example, and the mean K over the upper 100 or 200 meters of the ocean. Such an empirical finding greatly enhances the usefulness of this remotely sensed propagation parameter. Examples of the type of information being produced and archived for the atlas are presented.

Austin, R. W.↗
NASA NTRS1983

The effects of vegetation and soil hydraulic properties on passive microwave sensing of soil moisture: Data report for the 1982 fiels experiments

Field experiments to (1) study the biomass and geometrical structure properties of vegetation canopies to determine their impact on microwave emission data, and (2) to verify whether time series microwave data can be related to soil hydrologic properties for use in soil type classification. Truck mounted radiometers at 1.4 GHz and 5 GHz were used to obtain microwave brightness temperatures of bare vegetated test plots under different conditions of soil wetness, plant water content and canopy structure. Observations of soil moisture, soil temperature, vegetation biomass and other soil and canopy parameters were made concurrently with the microwave measurements. The experimental design and data collection procedures for both experiments are documented and the reduced data are presented in tabular form.

Oneill, P.↗
NASA NTRS1984

Effects of corn stalk orientation and water content on passive microwave sensing of soil moisture

A field experiment was conducted utilizing artificial arrangements of plant components during the summer of 1982 to examine the effects of corn canopy structure and plant water content on microwave emission. Truck-mounted microwave radiometers at C (5 GHz) and L (1.4 GHz) band sensed vertically and horizontally polarized radiation concurrent with ground observations of soil moisture and vegetation parameters. Results indicate that the orientation of cut stalks and the distribution of their dielectric properties through the canopy layer can influence the microwave emission measured from a vegetation/soil scene. The magnitude of this effect varies with polarization and frequency and with the amount of water in the plant, disappearing at low levels of vegetation water content. Although many of the canopy structures and orientations studied in this experiment are somewhat artificial, they serve to improve understanding of microwave energy interactions within a vegetation canopy and to aid in the development of appropriate physically based vegetation models.

Oneill, P. E.↗
NASA NTRS1989

Passive microwave sensing of the atmosphere

The development of microwave instrumetns to sound the atmosphere is reveiwed, focusing on the Advanced Microwave Sounding Unit (AMSU). The AMSU is planned for operation in a geosynchronous orbit or in LEO near 118 GHz. The three main AMSU subsystems are described: a 15-channel temperature sounder with a 50-km resolution, a 5-channel atmospheric moisture sounder with a 15-km resolution, and a 7-channel stratospheric and mesospheric temperature sounder with 150-km resolution. In addition, the potential for limb-sounding instruments is considered.

Staelin, David H.↗
NASA NTRS2001

Satellite Remote Sensing: Passive-Microwave Measurements of Sea Ice

Satellite passive-microwave measurements of sea ice have provided global or near-global sea ice data for most of the period since the launch of the Nimbus 5 satellite in December 1972, and have done so with horizontal resolutions on the order of 25-50 km and a frequency of every few days. These data have been used to calculate sea ice concentrations (percent areal coverages), sea ice extents, the length of the sea ice season, sea ice temperatures, and sea ice velocities, and to determine the timing of the seasonal onset of melt as well as aspects of the ice-type composition of the sea ice cover. In each case, the calculations are based on the microwave emission characteristics of sea ice and the important contrasts between the microwave emissions of sea ice and those of the surrounding liquid-water medium.

Parkinson, Claire L.↗
NASA NTRS2005

Passive Remote Sensing of Aerosols

Remote sensing of aerosol optical and microphysical properties got a resurgence in the 1970s when John Reagan and Ben Herman initiated a program to develop and implement a surface-based sunphotometer system to monitor spectral aerosol optical thickness at the University of Arizona. In this presentation I will review the state of the technology used to monitor aerosol optical and microphysical properties, including the determination of spectral aerosol optical thickness and total ozone content. This work continued with John Reagan developed a surface-based spectral flux radiometer to implement Ben Herman's idea to determine the imaginary part of the complex refractive index of aerosols using the recently developed diffuse-direct technique. Progress made both in surface-based instrumentation, inversion theory for analyzing such data, and in satellite observations of aerosol optical and microphysical properties will be reviewed to highlight the state of knowledge after 30 years of expanded capability and introduction of novel new capabilities, both from the ground and from spacecraft.

King, Michael D.↗