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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 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
DOE OSTI2025

University of Miami G-band Vapor Radiometer Calibration (UMGVR_CAL) Field Campaign Report

Cold-air outbreak (CAO) clouds in the Arctic are commonly mixed-phase (MP); however, the partitioning of the amount of ice and water in CAO clouds and precipitation is not always well observed. Understanding how cloud phases partition as a function of cloud life cycle is important for predicting snowfall rates, convective life cycle, and intensity at weather timescales. The partitioning into liquid versus ice also has radiative impacts that are consequential for climate. These concerns motivated the incorporation of an airborne G-band vapor radiometer (GVR) into an National Science Foundation-supported aircraft campaign named the Cold Air outbreak Experiment in the Sub-Arctic Region (CAESAR). The GVR is an upward-pointing passive microwave radiometer using four frequencies centered around the 183.31 GHz water vapor absorption line, displaced by +- 1, 3, 7, and 14 GHz. For context, The U.S. Department of Energy (DOE)’s Atmospheric Radiation Measurement (ARM) user facility operates a surface-based GVR at its North Slope of Alaska (NSA) site. The same GVR has been used previously for a field campaign in the southeast Pacific, where an offset was noticed between brightness temperatures (Tbs) measured under clear skies compared to those calculated from a radiative transfer model. To account for any calibration offsets to the Tbs, a request was made to DOE to allow the GVR to operate at ARM’s Southern Great Plains (SGP) observatory and enable comparisons between its measurements and those available at SGP. This request was granted, titled ‘UMGVR_CAL’, short for ‘UMGVR_Calibration’. From October 30 to November 10, 2023, the GVR was deployed to the ARM SGP site to take advantage of their regular, nearby radiosonde launches under clear-sky conditions. The latter were determined using the SGP total sky imagery data. The GVR brightness temperatures in these clear-sky conditions were compared to those calculated by a radiative transfer code (PAMTRA) based on the SGP radiosondes. During the campaign, four suitable clear-sky episodes could be used for the GVR calibration. While few in number, these proved to be enough to satisfy our goal.

54 ENVIRONMENTAL SCIENCES↗
NASA NTRS1967

An Evaluation of Sea Surface Temperature as Measured by the Nimbus 1 High Resolution Infrared Radiometer

An analysis of Nimbus I HRIR data over various parts of the world indicated limited success in deriving sea surface temperatures to within 3 to 6 K of aircraft radiation measurements (8- 13 microns) and synoptic-climatological ship sea surface temperature data. The areas studied included the east, west and Gulf coasts of the United States, West Greenland, Nova Scotia, southern Japan, the eastern Mediterranean Sea, Caspian Sea, Persian Gulf, and the Indian Ocean. At night, thin clouds which may fill the radiometer's field of view make it difficult to interpret the absolute values of derived sea surface temperature. During the daytime, the HRIR data is unusable for oceanographic temperature analysis because the contamination by reflected solar radiation mixes with the emitted radiation. Future satellite instrumentation, consisting of a HFUR radiometer (10-11 microns) when used in conjunction with television. data, will delineate cloud free ocean areas and permit the daily derivation of sea surface temperatures from approximately 10 to 30 Percent of the world's oceanic regions.

Allison, Lewis J.↗
NASA NTRS1971

Attitude-referenced radiometer study. Part 2: Primary calibration system

A primary calibration system, PCS, for infrared radiometers has been developed, built, and tested. The system allows radiometers to be calibrated with less than 1 percent error for use in earth coverage horizon measurements, earth resources surveys, and synoptic meteorological measurement. The final design, fabrication and test of the PCS are reported. A detailed description of the PCS construction is presented, along with the results of a complete series of functional tests. Test to verify the source thermal characteristics, collimator reflectance, and output beam characteristics are described and their results presented.

Williamson, W. R.↗
NASA NTRS1972

Salinity surveys using an airborne microwave radiometer

The Barnes PRT-5 infrared radiometer and L-band channel of the multifrequency microwave radiometer are used to survey the distribution of surface water temperature and salinity. These remote sensors were flown repetitively in November 1971 over the outflow of the Mississippi River into the Gulf of Mexico. Data reduction parameters were determined through the use of flight data obtained over a known water area. With these parameters, the measured infrared and microwave radiances were analyzed in terms of the surface temperature and salinity.

Paris, J. F.↗
NASA NTRS1972

Soil moisture measurements with microwave, radiometers

One technique of measuring moisture content that appears promising is that of microwave radiometry. In the microwave region of the spectrum, the emissivity of water is approximately 0.4, whereas that of dry soil is approximately 0.9. Therefore, the emissivity of the soil can range from about 0.6 to 0.9 as the soil changes from a wet to a dry condition. Recent ground base measurements have demonstrated emissivity changes of this magnitude. To test the use of this approach for remote sensing of soil moisture, flights were made over agricultural test sites in the vicinity of Phoenix, Ariz., during late February 1971. On the same day, soil moisture measurements were made on the ground for 200 fields. On board the aircraft were six microwave radiometers, ranging in wavelength from 21 cm to 8 mm. The results of one of these radiometers are presented.

Schmugge, T. J.↗
NASA NTRS1972

Arctic ice measurements with microwave radiometers

The application of microwave radiometers for measuring Arctic ice is discussed. The acquisition of Arctic ice data simultaneously on the surface with conventional instruments and remotely with microwave and infrared radiometers, photography, and a laser geodolite is described. A multifrequency view of a large multilayer ice floe is presented. The significance of the data recordings is explained.

Gloersen, P.↗
NASA NTRS1972

Smoke Plume Analysis Using Fan-beam and Single-beam Radiometers

Smoke plume data were taken using the stacks of the Mills Road Steam Plant on Redstone Arsenal, Huntsville, Alabama. The fan-beam unit was placed approximately 235 meters east of the Mills Road Steam Plant, and the single-beam unit was placed approximately 80 meters north of the fan-beam unit. Results of the smoke plume measurements indicate that the smoke plume is a periodic process near the mouth of the smokestack. The usefulness of the system is limited because of inaccurate and cumbersome positioning methods and base line constraints due to cable length. It is recommended that the radiometers be mounted on pedestals which have both azimuth and elevation positions determined by digitally controlled stepper drive motors. It is also recommended that a time multiplex system be used to transmit data from the radiometers to the electronics van.

Dodd, J. L.↗
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 NTRS1973

Electrically scanning microwave radiometer for Nimbus E

An electronically scanning microwave radiometer system has been designed, developed, and tested for measurement of meteorological, geomorphological and oceanographic parameters from NASA/GSFC's Nimbus E satellite. The system is a completely integrated radiometer designed to measure the microwave brightness temperature of the earth and its atmosphere at a microwave frequency of 19.35 GHz. Calibration and environmental testing of the system have successfully demonstrated its ability to perform accurate measurements in a satellite environment. The successful launch and data acquisition of the Nimbus 5 (formerly Nimbus E) gives further demonstration to its achievement.

Source record↗
NASA NTRS1972

An economical net solar flux radiometer.

The theory and design of an economical solar flux radiometer readily adaptable to the conventional radiosonde system are presented in response to the need cited by the Atmospheric Radiation Working Group (1971) for the development of an inexpensive light-weight short-wave radiometer sonde. Prototype instrument tests and current modifications are discussed. It is shown that the basic instrument can be easily modified to measure separately the upward and downward directed flux components, in addition to the net flux.

Darkow, G. L.↗
NASA NTRS1973

Investigations of atmospheric extinction using direct solar radiation measurements made with a multiple wavelength radiometer.

A multiple wavelength solar radiometer designed for the purpose of measuring atmospheric optical depth at discrete wavelengths through the visible region is described. Experimental techniques, including sample observations, are presented for obtaining atmospheric optical depth from radiometer measurements. These techniques apply for conditions where the optical depth is either temporally variant or invariant during the course of a day. The influence of the aerosol size distribution on optical depth is investigated. Theoretical calculations of the wavelength dependency of the aerosol optical depth contribution are presented for several representative aerosol size distributions. Methods are also presented for estimating the aerosol size distribution and aerosol mass loading from multiwavelength optical depth measurements.

Shaw, G. E.↗
NASA NTRS1973

Very high resolution radiometer /VHRR/

Discussion of the design and performance of the very high resolution radiometer (VHRR) representing the first of a second-generation of infrared scanning radiometers of high performance. Following a description of the optical, signal-electronics, sync-generator, scan-drive, cooler, and contamination-protection design, it is pointed out that the two VHRRs presently operating have logged a total of 15,500 hrs of continuous successful operation since launch. The cooler operation has been particularly noteworthy. The cold plate heater power, required to maintain the detectors at 105 K, has undergone in almost a year's operation so small a degradation as to indicate a VHRR cooler lifetime exceeding the instrument design lifetime of one year by a large margin. High resolution, low noise, and jitter-free pictures are shown to have been derived from these instruments.

Aronson, A. I.↗
NASA NTRS1973

Transmission of radiometer data from the Synchronous Meteorological Satellite

The Synchronous Meteorological Satellite uses a spin scanner radiometer which generates eight visual signals and two infrared signals. These signals are multiplexed and converted into a 28-Mbps data stream. This signal is transmitted to ground by quadriphase modulation at 1686.1 MHz. On the ground, the digital signal is reconstructed to an analog signal. To conserve bandwidth, an analog-to-digital converter with a nonlinear transfer function was used for the visual signals. The size of the quantization step was made proportional to the noise output of the scanner photomultiplier tube which increases as the square root of incident light. The radiometer data transmission link was simulated on a digital computer to determine the transfer function. Some results of the simulation are shown.

Davies, R. S.↗
NASA NTRS1974

An S-band radiometer design with high absolute precision

A radiometer for the remote measurement of sea surface temperature is described. The development of an instrument capable not only of high relative accuracy (i.e., resolution) but also of high absolute precision is considered. The concepts underlying the design of an instrument capable of an absolute accuracy of a few tenths degrees Kelvin in the measurement of brightness temperature at S band are described. The role of the antenna is discussed, and the importance of high ohmic and beam efficiencies is stressed. The hardware itself is fully described, along with an outline concerning the design of a unique cryogenically cooled termination used to calibrate the whole radiometer, including antenna. Finally, some test results are presented that show that the design goals for the instrument have been closely approached.

Hardy, W. N.↗
NASA NTRS1974

Tropical cyclone rainfall as measured by the Nimbus 5 electrically scanning microwave radiometer

A selected group of 1973 North Pacific Ocean tropical cyclones was studied by using data from the Nimbus 5 Electrically Scanning Microwave Radiometer (ESMR), the Temperature-Humidity Infrared Radiometer (THIR), NOAA-2 and USAF DMSP imageries. From the unique combination of infrared, visible, and microwave data, it was possible during various stages of storm development to differentiate between dense cirrus outflow and rain areas, to identify centers of circulation and areas of low-level moisture, and by the use of a theoretical model to estimate semi-quantitatively areas of light, moderate, and heavy rainfall rates.

Allison, L. J.↗