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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 NTRS1990

Multiparameter radar and microwave radiative transfer modeling of nonspherical atmospheric ice particles

Multiparameter radar and polarized microwave radiative transfer models for arbitrarily shaped particles are developed. The ice crystals modeled are horizontally oriented hexagonal plates, columns, and needles. The ice water content is fixed at 0.1 g/cu m, and a realistic size distribution is used. The radar modeling is done for S through K-band, and the passive microwave calculations are at 37, 85, and 157 GHz. The modeling results show that particle shape is important for both multiparameter radar and passive microwave radiometry. Radar reflectivity and upwelling microwave brightness temperatures depend strongly on the individual particle volume, which in turn depends on the ice crystal shape. Radar differential reflectivity is high for the plates and lower for needles and columns. Linear depolarization calculations indicate that oblate ice crystals such as plates can be distinguished from prolate crystals such as columns. At 85 and 157 GHz, significant polarization brightness temperature differences are calculated for plates and columns. The particle bulk density strongly affects the radar and radiometer observables. Recent measurements of ice crystals are discussed to show that the model results have practical applicability.

Evans, K. Franklin↗
NASA NTRS1990

Global atmospheric temperature monitoring with satellite microwave measurements - Method and results 1979-84

This paper describes a method for determining global atmospheric-temperature anomalies by means of satellite microwave radiometry. It is shown that microwave measurements of molecular oxygen thermal emission by the Microwave Sounding Units (MSUs) flying aboard the NOAA-6 and NOAA-7 can be used to monitor tropospheric temperature anomalies on global basis to a high level of precision. Comparisons between monthly MSU-derived hemispheric temperature anomalies with those computed from surface thermometer data show a very good agreement over the United States, although not for the hemispheres, especially the Southern Hemisphere. In this latter case, the poor agreement is ascribed to weaker thermal coupling between the ocean and the deep troposphere than that over the U.S. Annual anomalies for the hemispheres exhibit better correlations than do monthly anomalies.

Spencer, Roy W.↗
NASA NTRS1973

Remote monitoring of soil moisture using airborne microwave radiometers

The current status of microwave radiometry is provided. The fundamentals of the microwave radiometer are reviewed with particular reference to airborne operations, and the interpretative procedures normally used for the modeling of the apparent temperature are presented. Airborne microwave radiometer measurements were made over selected flight lines in Chickasha, Oklahoma and Weslaco, Texas. Extensive ground measurements of soil moisture were made in support of the aircraft mission over the two locations. In addition, laboratory determination of the complex permittivities of soil samples taken from the flight lines were made with varying moisture contents. The data were analyzed to determine the degree of correlation between measured apparent temperatures and soil moisture content.

Kroll, C. L.↗
NASA NTRS1977

Data processing for the DMSP microwave radiometer system

A software program was developed and tested to process microwave radiometry data to be acquired by the microwave sensor (SSM/T) on the Defense Meteorological Satellite Program spacecraft. The SSM/T 7-channel microwave radiometer and systems data will be data-linked to Air Force Global Weather Central (AFGWC) where they will be merged with ephemeris data prior to product processing for use in the AFGWC upper air data base (UADB). The overall system utilizes an integrated design to provide atmospheric temperature soundings for global applications. The fully automated processing at AFGWC was accomplished by four related computer processor programs to produce compatible UADB soundings, evaluate system performance, and update the a priori developed inversion matrices. Tests with simulated data produced results significantly better than climatology.

Rigone, J. L.↗
NASA NTRS1993

Passive Microwave Remote Sensing for Land Resources

Spaceborne microwave radiometry is an important technique for obtaining global estimates of parameters important to Earth's hydrologic cycle, land resources, environmental monitoring, and climate. They key physical processes involved in these applications are the land-atmosphere exchanges of heat and moisture, and their status and variability on different time and space scales.

microwave radiometry hydrology land resources↗
NASA NTRS2007

Two-Dimensional Synthetic Aperture Radiometry over Land Surface During Soil Moisture Experiment in 2003 (SMEX03)

Microwave radiometry at low frequencies (L-band, approx. 1.4 GHz) has been known as an optimal solution for remote sensing of soil moisture. However, the antenna size required to achieve an appropriate resolution from space has limited the development of spaceborne L-band radiometers. This problem can be addressed by interferometric technology called aperture synthesis. The Soil Moisture and Ocean Salinity (SMOS) mission will apply this technique to monitor global-scale surface parameters in the near future. The first airborne experiment using an aircraft prototype of this approach, the Two-Dimensional Synthetic Aperture Radiometer (2D-STAR), was performed in the Soil Moisture Experiment in 2003 (SMEX03). The L-band brightness temperature data acquired in Alabama by the 2DSTAR was compared with ground-based measurements of soil moisture and with C-band data collected by the Polarimetric Scanning Radiometer (PSR). Our results demonstrate a good response of the 2D-STAR brightness temperature to changes in surface wetness, both in agricultural and forest lands. The behavior of the horizontally polarized brightness temperature data with increasing view-angle over the forest area was noticeably different than over bare soil. The results from the comparison of 2D-STAR and PSR indicate a better response of the 2D-STAR to the surface wetness under both wet and dry conditions. Our results have important implications for the performance of the future SMOS mission.

Ryu, Dongryeol↗
NASA NTRS2022

Mapping Firn Saturation over Greenland using NASA’s Soil Moisture Active Passive Satellite

Mapping the spatial extent of recently identified englacial hydrological features (i.e., ice slabs and perennial firn aquifers) formed by meters-thick water-saturated firn layers over the percolation facies of the Greenland Ice Sheet using L-band microwave radiometry has recently been demonstrated. However, these initial maps are binary, and do not provide a parameter to estimate the spatial variability in the thickness and volumetric fraction of meltwater stored within the firn pore space. Here, we exploit enhanced-resolution vertical-polarization L-band brightness temperature (T^(B)_(V)) imagery (2015–2019) generated using observations collected over Greenland by NASA’s Soil Moisture Active Passive (SMAP) satellite and a simple two-layer L-band brightness temperature model. We map water-saturated firn layers via a “firn saturation” parameter, and interpret our results together with ice slab and perennial firn aquifer spatial extents, estimates of snow accumulation simulated via the Regional Atmospheric Climate Model (RACMOp2.3), and airborne radar surveys collected via NASA’s Operation IceBridge (OIB) campaigns. We find that variable firn saturation parameter values are mapped in lower snow accumulation ice slab areas in western, northern, and northeastern Greenland, where firn is colder and water-saturated firn layers seasonally refreeze as solid-ice. Higher firn saturation parameter values are mapped in higher snow accumulation perennial firn aquifer areas in southeastern, southern, and northwestern Greenland, where firn is near the melting point, and meters-thick water-saturated firn layers exist. Our results have implications for identifying expansive englacial reservoirs that store significant volumes of meltwater in locations that are vulnerable to meltwater-induced hydrofracturing and accelerated outlet glacier flow year-round.

Greenland ice sheet↗
NASA NTRS1970

A study of passive microwave techniques applied to geologic problems

Passive microwave techniques were applied to geologic problems, in order to establish the microwave properties of representative rocks and minerals, and to examine the feasibility of using microwave radiometry for geologic mapping problems. A review of microwave pertaining to geology was conducted, coupled with laboratory and field investigations of the microwave emission characteristics of various geologic features. The laboratory studies consisted of dielectric constant measurements of rocks and minerals. A majority of field investigations conducted in the western United States, involved the microwave emission charateristics of rock types, and a portion of the study was concerned with microwave properties of mineralized areas. Experiments were also conducted in the vicinity of a coal seam fire in Colorado and across the San Andreas Fault Zone near the Salton Sea, in Southern California.

Edgerton, A. T.↗
NASA NTRSDate not supplied

Microwave and mm-Wave Radiometry for Earth and Planetary Science

Microwave radiometry has been an indispensable tool for observing Earth and the solar system since the 1960s. On Earth, microwave radiometers are used to observe ocean, land, ice, and atmosphere. Calibrating a microwave radiometer and measuring an LNA noise figure use the same principals. There is opportunity to improve upon the state-of-the-art methods in both space and lab environments by leveraging lessons learned in one for the other.

microwave radiometry↗
NASA NTRS1989

Passive microwave retrievals of rainfall and rain system structure

Consideration is given to the development of algorithms for the Tropical Rainfall Measuring Mission to retrieve rain and rain vertical structure from passive microwave radiometry. The self-consistency approach for surface rain rate retrieval of Kummerow et al. (1989) is applied to microwave brightness temperature data from the Cooperative Huntsville Meteorological Experiment (Dodge et al., 1986). Because the algorithm simultaneously retrieves rainfall rate and rain system structure, it is suggested that the algorithm can be used to overcome the problem of the dependence of brightness temperatures on the vertical profile of hydrometeors.

Kummerow, Christian↗
NASA NTRS1993

Microwave radiative transfer studies of precipitation

Since the deployment of the DMSP SSM/I microwave imagers in 1987, increased utilization of passive microwave radiometry throughout the 10 - 100 GHz spectrum has occurred for measurement of atmospheric constituents and terrestrial surfaces. Our efforts have focused on observations and analysis of the microwave radiative transfer behavior of precipitating clouds. We have focused particular attention on combining both aircraft and SSM/I radiometer imagery with ground-based multiparameter radar observations. As part of this and the past NASA contract, we have developed a multi-stream, polarized radiative transfer model which incorporates scattering. The model has the capability to be initialized with cloud model output or multiparameter radar products. This model provides the necessary 'link' between the passive microwave radiometer and active microwave radar observations. This unique arrangement has allowed the brightness temperatures (TB) to be compared against quantities such as rainfall, liquid/ice water paths, and the vertical structure of the cloud. Quantification of the amounts of ice and water in precipitating clouds is required for understanding of the global energy balance.

Bringi, V. N.↗
NASA NTRS1974

Antennas for spaceborne microwave radiometers

Principles and applications of microwave radiometry to remote sensing of the earth from satellites are reviewed. Examples of some spaceborne radiometer systems currently in use or under consideration are given. The requirements on performance characteristics of microwave antennas for such spaceborne earth sensing radiometers, such as coverage, scanning, spatial resolution, insertion loss, beam efficiency, polarization purity, etc., and their effects on the overall radiometer system performance are discussed.

Shiue, J. C.-C.↗
NASA NTRS2001

Feasibility Study of Radiometry for Airborne Detection of Aviation Hazards

Radiometric sensors for aviation hazards have the potential for widespread and inexpensive deployment on aircraft. This report contains discussions of three aviation hazards - icing, turbulence, and volcanic ash - as well as candidate radiometric detection techniques for each hazard. Dual-polarization microwave radiometry is the only viable radiometric technique for detection of icing conditions, but more research will be required to assess its usefulness to the aviation community. Passive infrared techniques are being developed for detection of turbulence and volcanic ash by researchers in this country and also in Australia. Further investigation of the infrared airborne radiometric hazard detection approaches will also be required in order to develop reliable detection/discrimination techniques. This report includes a description of a commercial hyperspectral imager for investigating the infrared detection techniques for turbulence and volcanic ash.

Gimmestad, Gary G.↗
NASA NTRS1974

A study program on large aperture electronic scanning phased array antennas for the shuttle imaging microwave system

Fundamental phased array theory and performance parameters are discussed in terms of their application to microwave radiometry, and four scanning phased arrays representing current examples of state-of-the-art phased array technology are evaluated for potential use as components of the multispectral antenna system for the space shuttle imaging microwave system (SIMS). A discussion of problem areas, both in performance and fabrication is included, with extrapolations of performance characteristics for phased array antennas of increased sizes up to 20 m by 20 m. The possibility of interlacing two or more phased arrays to achieve a multifrequency aperture is considered, and, finally, a specific antenna system is recommended for use with SIMS.

Source record↗
NASA NTRS1977

Microwave remote sensing from space for earth resource surveys

The concepts of radar remote sensing and microwave radiometry are discussed and their utility in earth resource sensing is examined. The direct relationship between the character of the remotely sensed data and the level of decision making for which the data are appropriate is considered. Applications of active and a passive microwave sensing covered include hydrology, land use, mapping, vegetation classification, environmental monitoring, coastal features and processes, geology, and ice and snow. Approved and proposed microwave sensors are described and the use of space shuttle as a development platform is evaluated.

Source record↗
NASA NTRS2008

Testing of Cloud Microphysics Scheme with Snow Events

One of the grand challenges of the Global Precipitation Measurement (GPM) mission is to improve precipitation measurements in mid- and high-latitudes during cold seasons through the use of high-frequency passive microwave radiometry. For this, the Weather Research Forecast (WRF) model with the Goddard microphysics scheme is coupled with the Satellite Data Simulation Unit (WRF-SDSU) that has been developed to facilitate the over-snowfall retrieval algorithm by providing virtual cloud library and microwave brightness temperature (To) measurements consistent to the GPM Microwave Imager (GMI). This study tested the Goddard cloud microphysics scheme in WRF in snowstorm events (January 20-22, 2007) over the Canadian CloudSat/CALIPSO Validation Project (C3VP) site up in Ontario, Canada. In this meeting, we will present the performance of the Goddard cloud microphysics scheme both with 2ice (ice and snow) and 3ice (ice, snow and graupel) as well as other WRF microphysics schemes. Results will be compared with the King Radar data. We will also use the WRF model outputs to drive the Goddard SDSU to calculate radiances and backscattering signals consistent to satellite direct observations. These simulated radiance are evaluated against the measurement from A-Train satellites.

Tao, Wei-Kuo↗
NASA NTRS1982

Passive microwave remote sensing of the earth from space - A review

A brief discussion of the historical development of microwave radiometry from space is provided, followed by a review of radiometer system concepts as applied to spacecraft platforms. One of the earliest meteorological applications of spaceborne radiometry was in global atmospheric temperature sounding. Surface-sensing applications can be divided into three main categories, including ocean, ice, and land. A radiometer system description is presented, and spacecraft considerations are discussed. Spaceborne radiometric sensors are examined, taking into account the Nimbus-5 Microwave Spectrometer, the Electrically Scanning Microwave Radiometer, the Skylab microwave radiometer/scatterometer and altimeter instrument, S-194 on Skylab, the Scanning Microwave Spectrometer on Nimbus 6, the Scanning Multichannel Microwave Radiometer on Seasat and Nimbus 7, Soviet sensors, and an Indian microwave radiometer.

Njoku, E. G.↗