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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 235 records · Page 13
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

A technique for measuring vertically and horizontally polarized microwave brightness temperatures using electronic polarization-basis rotation

This technique for electronically rotating the polarization basis of an orthogonal-linear polarization radiometer is based on the measurement of the first three feedhorn Stokes parameters, along with the subsequent transformation of this measured Stokes vector into a rotated coordinate frame. The technique requires an accurate measurement of the cross-correlation between the two orthogonal feedhorn modes, for which an innovative polarized calibration load was developed. The experimental portion of this investigation consisted of a proof of concept demonstration of the technique of electronic polarization basis rotation (EPBR) using a ground based 90-GHz dual orthogonal-linear polarization radiometer. Practical calibration algorithms for ground-, aircraft-, and space-based instruments were identified and tested. The theoretical effort consisted of radiative transfer modeling using the planar-stratified numerical model described in Gasiewski and Staelin (1990).

Gasiewski, Albin J.↗
NASA NTRS1991

A physical interpretation of brightness temperatures observed by the microwave sounding units based upon raobs

Ten years (1979-1988) of Microwave Sounding Unit (MSU) data from five satellites were calibrated and processed using procedures described by Spence and Christy (1990) and Spenser et al. (1990). The data are averaged at one month and 2.5-deg grid resolution, and the monthly anomalies in channel 2 are computed from annual cycles measured at each gridpoint. The anomalies at gridpoints are then compared with anomalies computed from radiosonde data.

Spencer, Roy W.↗
NASA NTRS1992

Spatial resolution enhancement of terrestrial features using deconvolved SSM/I microwave brightness temperatures

A method for enhancing the 19, 22, and 37 GHz measurements of the SSM/I (Special Sensor Microwave/Imager) to the spatial resolution and sampling density of the high resolution 85-GHz channel is presented. An objective technique for specifying the tuning parameter, which balances the tradeoff between resolution and noise, is developed in terms of maximizing cross-channel correlations. Various validation procedures are performed to demonstrate the effectiveness of the method, which hopefully will provide researchers with a valuable tool in multispectral applications of satellite radiometer data.

Farrar, Michael R.↗
NASA NTRS1996

Estimating the Thickness of Sea Ice Snow Cover in the Weddell Sea from Passive Microwave Brightness Temperatures

Passive microwave satellite observations have frequently been used to observe changes in sea ice cover and concentration. Comiso et al. showed that there may also be a direct relationship between the thickness of snow cover (h(sub s)) on ice and microwave emissivity at 90 GHz. Because the in situ experiment of experiment of Comiso et al. was limited to a single station, the relationship is re-examined in this paper in a more general context and using more extensive in situ microwave observations and measurements of h from the Weddell Sea 1986 and 1989 winter cruises. Good relationships were found to exist between h(sub s) sand the emissivity at 90 GHz - 10 GHz and the emissivity at 90 GHz - 18.7 GHz when the standard deviation of h(sub s) was less than 50% of the mean and when h(sub s) was less than 0.25 m. The reliance of these relationships on h(sub s) is most likely caused by the limited penetration through the snow of radiation at 90 GHz. When the algorithm was applied to the Special Sensor Microwave/Imager (SSM/I) satellite data from the Weddell Sea, the resulting mean h(sub s) agreed within 5% of the mean calculated from greater than 1400 in situ observations.

Arrigo, K. R.↗
NASA NTRS1999

Generation of Level 3 SMMR and SSM/I Brightness Temperatures for the Period 1978-1999

The NOAA/NASA Pathfinder Program was initially designed to assure that certain key remote sensing data sets of particular significance to global change research were scientifically validated, consistently processed and made readily available to the research community at minimal cost. Through this Program the National Snow and Ice Data Center (NSIDC), University of Colorado has successfully processed, archived and distributed the Scanning Multichannel Microwave Radiometer (SMMR) and Special Sensor Microwave/Imager (SSM/I) Level 3 (EASE-Grid format) Pathfinder data sets for the period 1978 to 1999. These data are routinely distributed to approximately 150 researchers through various media including CD-ROM, 8 mm tape, ftp and the EOS Information Management System (IMS). At NSIDC these data are currently being applied in the development and validation of algorithms to derive snow water equivalent (NASA NAG5-6636), the mapping of frozen ground and the detection of the onset of melt over ice sheets, sea ice and snow cover. The EASE-Grid format, developed at NSIDC in conjunction with the SMMR-SSM/I Pathfinder project has also been applied to Advanced Very High Resolution Radiometer (AVHRR) and TOVS Pathfinder data, as well as ancillary data such as digital elevation, land cover classification and several in situ data sets. EASE-Grid will also be used for all land products derived from the NASA EOS AMSR-E instrument.

Partington, Kim↗
NASA NTRS2003

Combined Radiometer-Radar Microphysical Profile Estimations with Emphasis on High Frequency Brightness Temperature Observations

Information about the vertical microphysical cloud structure is useful in many modeling and predictive practices. Radiometers and radars are used to observe hydrometeor properties. This paper describes an iterative retrieval algorithm that combines the use of airborne active and wideband (10 to 340 GHz) passive observations to estimate the vertical content and particle size distributions of liquid and frozen hydrometeors. The physically-based retrieval algorithm relies on the high frequencies (greater than 89 GHz) to provide details on the frozen hydrometeors. Neglecting the high frequencies yielded acceptable estimates of the liquid profiles, but the ice profiles were poorly retrieved. Airborne radar and radiometer observations from the third Convection and Moisture EXperiment (CAMEX-3) were used in the retrieval algorithm as constraints. Nadir profiles were estimated for a minute each of flight time (approximately 12.5 km along track) from an anvil, convection, and quasi- stratiform rain. The complex structure of the frozen hydrometeors required the most iterations for convergence for the anvil cloud type. The wideband observations were found to more than double the estimated frozen hydrometeor content as compared to retrievals using only 90-GHz and below. The convective and quasi-stratiform quickly reached convergence (minimized difference between observations and calculations using the estimated profiles). A qualitative validation using coincident in situ CAMEX-3 observations shows that the retrieved particle size distributions are well corroborated with independent measurements.

Gail Skofronick-Jackson↗
NASA NTRS2002

Simulation of TRMM Microwave Imager Brightness Temperature using Precipitation Radar Reflectivity for Convective and Stratiform Rain Areas over Land

Rain is highly variable in space and time. In order to measure rainfall over global land with satellites, we need observations with very high spatial resolution and frequency in time. On board the Tropical Rainfall Measuring Mission (TRMM) satellite, the Precipitation Radar (PR) and Microwave Imager (TMI) are flown together for the purpose of estimating rain rate. The basic method to estimate rain from PR has been developed over the past several decades. On the other hand, the TMI method of rain estimation is still in the state development, particularly over land. The objective of this technical memorandum is to develop a theoretical framework that helps relate the observations made by these two instruments. The principle result of this study is that in order to match the PR observations with the TMI observations in convective rain areas, a mixed layer of graupel and supercooled water drops above the freezing level is needed. On the other hand, to match these observations in the stratiform region, a layer of snowflakes with appropriate densities above the freezing level, and a melting layer below the freezing level, are needed. This understanding can lead to a robust rainfall estimation technique from the microwave radiometer observations.

Prabhakara, C.↗
NASA NTRS1999

Algorithm Theoretical Basis Document for: Brightness Temperature

The Advanced Spaceborne Thermal Emission and Reflectance Radiometer (ASTER) is a high-spatial-resolution multispectral imaging device scheduled to fly in Earth orbit starting in mid-1999, on the first platform of NASA's Earth Observing System (EOS-AM 1.

ASTER thermal infrared temperature algorithm D-139↗
NASA NTRS2012

Observations of C-band Brightness Temperature from the Hurricane Imaging Radiometer (HIRAD) During GRIP

HIRAD is a new technology developed by NASA/MSFC, in partnership with NOAA and the Universities of Central Florida, Michigan, and Alabama-Huntsville. HIRAD is designed to measure wind speed and rain rate over a wide swath in heavy-rain, strong-wind conditions. HIRAD is expected to eventually fly routinely on unmanned aerial vehicles (UAVs) such as Global Hawk over hurricanes threatening the U.S. coast and other Atlantic basin areas, and possibly in the Western Pacific as well. HIRAD first flew on GRIP in 2010 and is planned to fly 2012-14 on the NASA Hurricane and Severe Storm Sentinel (HS3) missions on the Global Hawk, a high-altitude UAV. HIRAD technology will eventually be used on a satellite platform to extend the dynamical range of Ocean Surface Wind (OSV) observations from space.

Miller, Timothy L.↗