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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 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1979

Satellite communications for disaster relief operations

The use of existing and planned communication satellite systems to provide assistance in the implementation of disaster relief operations on a global basis was discussed along with satellite communications system implications and their potential impact on field operations in disaster situations. Consideration are given to the utilization of both INTELSAT and MARISAT systems operating at frequencies ranging from 1.5 to 4 GHz and to the size and type of ground terminals necessary for satellite access. Estimates of communication requirements for a global system are given. Some discussion of cost estimates for satellite services to support operations are included. Studies of communication satellites for both pre and post disaster applications conducted for NOAA are included as well as recent experiments conducted in conjunction with the Office of Foreign Disaster Assistance of the Agency for International Development.

Sivo, J. N.↗
NASA NTRS1980

Submillimeter, millimeter, and microwave spectral line catalogue

A computer accessible catalogue of submillimeter, millimeter, and microwave spectral lines in the frequency range between O and 3000 GHz (such as; wavelengths longer than 100 m) is discussed. The catalogue was used as a planning guide and as an aid in the identification and analysis of observed spectral lines. The information listed for each spectral line includes the frequency and its estimated error, the intensity, lower state energy, and quantum number assignment. The catalogue was constructed by using theoretical least squares fits of published spectral lines to accepted molecular models. The associated predictions and their estimated errors are based upon the resultant fitted parameters and their covariances.

Poynter, R. L.↗
NASA NTRS1979

The use of geostationary platforms for future U.S. domestic satellite communications

Quantitative analyses of the relative costs and utilization of the available geostationary orbital arc and radio spectrum allocations between large spacecraft platforms and future individual satellites used for communications in the U.S. and the Atlantic Basin are presented. Attention is given to the high capacity and the switching capabilities of the platforms, and the frequency ranges (6/4, 14/12, and 30/20 GHz) at which they can operate. In addition, characteristics of conventional satellites, earth station design, and the connectivity of satellite systems are discussed.

Fordyce, S.↗
NASA NTRS1980

Snow Electromagnetic Measurements

An electromagnetic system is described for measuring the dielectric constant and attenuation of snow samples in the frequency range of 4 to 12 GHz. System components consists of a swept-frequency source, microwave horns, network analyzer, and XY plotter. The procedure for calibrating the effect of wetness on the snow properties is described. Equations are given that express the experimentally determined relation between attenuation per unit length and volume percent wetness at any frequency between 4 and 12 GHz. permittivity can be calculated from the snow density, attenuation per unit length, and frequency. Some applications of the techniques are described such as runoff forecasting from mountain snowpacks.

Linlor, W. I.↗
NASA NTRS1981

Submillimeter, millimeter, and microwave spectral line catalogue

A computer accessible catalogue of submillimeter, millimeter and microwave spectral lines in the frequency range between 0 and 3000 GHZ (i.e., wavelengths longer than 100 mu m) is presented which can be used a planning guide or as an aid in the identification and analysis of observed spectral lines. The information listed for each spectral line includes the frequency and its estimated error, the intensity, lower state energy, and quantum number assignment. The catalogue was constructed by using theoretical least squares fits of published spectral lines to accepted molecular models. The associated predictions and their estimated errors are based upon the resultant fitted parameters and their covariances. Future versions of this catalogue will add more atoms and molecules and update the present listings (133 species) as new data appear. The catalogue is available as a magnetic tape recorded in card images and as a set of microfiche records.

Poynter, R. L.↗
NASA NTRS1981

The Norwegian remote sensing experiment (Norsex) in a marginal ice zone

Passive and active microwave measurements from surface based, airborne, and satellite instruments were obtained together with surface observations northwest of Svalbard. Emissivities of different ice patches in the ice edge region over the spectral range from 4.9 to 94 GHz are presented. The combination of a 6.6 GHz microwave radiometer with a 14.6 GHz scatterometer demonstrates the usefulness of an active/passive system in ice classification. A variety of mesoscale features under different meteorological conditions is revealed by a 1.36 GHz synthetic aperture radar. Ice edge location by Nimbus 7 scanning multifrequency microwave radiometer is shown accurate to 10 km when the 37 GHz horizontal polarized channel is used.

Farrelly, B.↗
NASA NTRS1982

Limitations imposed by ionospheric turbulence on satellite-to-satellite Doppler measurement accuracy

For some time the possibility has been considered to perform an accurate survey from orbit of the earth gravity field by making use of low-low, satellite-to-satellite Doppler tracking with a radio link which operates in the frequency band in the range from 50 to 100 GHz. It is, therefore, of interest to discuss the upper bound in Doppler measurement accuracy imposed by the effects of ionospheric turbulence. The present investigation is concerned with the measurement error induced by ionospheric turbulence. The assumptin is made that the so-called ionospheric refractive 'bias' can be removed with one of the multifrequency methods of the current practice.

Grossi, M. D.↗
NASA NTRS1984

Catalog of Spectral Lines

Report describes computer accessible catalog of calculated and experimental spectral lines in frequency range between zero and 300 GHz for selected molecules, including chlorine oxide, bromine oxide, phosphine and oxygen.

Poynter, R. L.↗
NASA NTRS1982

The 15-meter diameter mechanically scanned deployable antenna

A preliminary design with structural model data and thermal-performance estimates of a 15-meter mechanically scanned deployable antenna (MSDA) that could be launched onboard a Shuttle Orbiter to provide radiometric brightness temperature maps of the Earth and oceans in selected bands over a frequency range from 1.4 to 11 GHz is provided. The study objectives were met through the design of a unique, integrated, offset feed mast and reflector design that uses the deployable box-truss structure as a building block. The performance of this system is summarized. The all graphite-epoxy, 4.57-meter prototype cube that was completed in 1981 and is proposed for this reflector and feed mast design is presented.

Coyner, J. V.↗
NASA NTRS1983

GaAs microwave devices and circuits with submicron electron-beam defined features

This paper describes the fabrication and application of GaAs FET's, both as discrete microwave devices and as the key active components in monolithic microwave integrated circuits. The performance of these devices and circuits is discussed for frequencies ranging from 3 to 25 GHz. The crucial fabrication step is the formation of the submicron gate by electron-beam lithography.

Wisseman, W. R.↗
NASA NTRS1984

Inversion algorithms for the microwave remote sensing of soil moisture. Experiments with swept frequency microwaves

Two experiments were performed employing swept frequency microwaves for the purpose of investigating the reflectivity from soil volumes containing both discontinuous and continuous changes in subsurface soil moisture content. Discontinuous moisture profiles were artificially created in the laboratory while continuous moisture profiles were induced into the soil of test plots by the environment of an agricultural field. The reflectivity for both the laboratory and field experiments was measured using bi-static reflectometers operated over the frequency ranges of 1.0 to 2.0 GHz and 4.0 to 8.0 GHz. Reflectivity models that considered the discontinuous and continuous moisture profiles within the soil volume were developed and compared with the results of the experiments. This comparison shows good agreement between the smooth surface models and the measurements. In particular the comparison of the smooth surface multi-layer model for continuous moisture profiles and the yield experiment measurements points out the sensitivity of the specular component of the scattered electromagnetic energy to the movement of moisture in the soil.

Hancock, G. D.↗
NASA NTRS1984

Submillimeter, millimeter, and microwave spectral line catalogue

This report describes a computer accessible catalogue of submillimeter, millimeter, and microwave spectral lines in the frequency range between 0 and 10000 GHz (i.e., wavelengths longer than 30 micrometers). The catalogue can be used as a planning guide or as an aid in the identification and analysis of observed spectral lines. The information listed for each spectral line includes the frequency and its estimated error, the intensity, lower state energy, and quantum number assignment. The catalogue has been constructed using theoretical least squares fits of published spectral lines to accepted molecular models. The associated predictions and their estimated errors are based upon the resultant fitted parameters and their covariances. Future versions of this catalogue will add more atoms and molecules and update the present listings (151 species) as new data appear. The catalogue is available from the authors as a magnetic tape recorded in card images and as a set of microfiche records.

Poynter, R. L.↗
NASA NTRS1985

Submillimeter, millimeter, and microwave spectral line catalog

This report describes a computer accessible catalogue of submillimeter, millimeter, and microwave spectral lines in the frequency range between 0 and 10000 GHz (i.e., wavelengths longer than 30 micrometers). The catalogue can be used as a planning guide or as an aid in the identification and analysis of observed spectral lines. The information listed for each spectral line includes the frequency and its estimated error, the intensity, lower state energy, and quantum number assignment. The catalogue has been constructed using theoretical least squares fits of published spectral lines to accepted molecular models. The associated predictions and their estimated errors are based upon the resultant fitted parameters and their covariances. Future versions of this catalogue will add more atoms and molecules and update the present listings (151 species) as new data appear. The catalogue is available from the authors as a magnetic tape recorded in card images and as a set of microfiche records.

Poynter, R. L.↗
NASA NTRS1986

Swept frequency technique for dispersion measurement of microstrip lines

Microstrip lines used in microwave integrated circuits are dispersive. Because a microstrip line is an open structure, the dispersion can not be derived with pure TEM, TE, or TM mode analysis. Dispersion analysis has commonly been done using a spectral domain approach, and dispersion measurement has been made with high Q microstrip ring resonators. Since the dispersion of a microstrip line is fully characterized by the frequency dependent phase velocity of the line, dispersion measurement of microstrip lines requires the measurement of the line wavelength as a function of frequency. In this paper, a swept frequency technique for dispersion measurement is described. The measurement was made using an automatic network analyzer with the microstrip line terminated in a short circuit. Experimental data for two microstrip lines on 10 and 30 mil Cuflon substrates were recorded over a frequency range of 2 to 20 GHz. Agreement with theoretical results computed by the spectral domain approach is good. Possible sources of error for the discrepancy are discussed.

Lee, R. Q.↗
NASA NTRS1988

Optically interconnected phased arrays

Phased-array antennas are required for many future NASA missions. They will provide agile electronic beam forming for communications and tracking in the range of 1 to 100 GHz. Such phased arrays are expected to use several hundred GaAs monolithic integrated circuits (MMICs) as transmitting and receiving elements. However, the interconnections of these elements by conventional coaxial cables and waveguides add weight, reduce flexibility, and increase electrical interference. Alternative interconnections based on optical fibers, optical processing, and holography are under evaluation as possible solutions. In this paper, the current status of these techniques is described. Since high-frequency optical components such as photodetectors, lasers, and modulators are key elements in these interconnections, their performance and limitations are discussed.

Bhasin, Kul B.↗
NASA NTRS1988

A role for high frequency superconducting devices in free space power transmission systems

Major advances in space power technology are being made in photovoltaic, solar thermal, and nuclear systems. Despite these advances, the power systems required by the energy and power intensive mission of the future will be massive due to the large collecting surfaces, large thermal management systems, and heavy shielding. Reducing this mass on board the space vehicle can result in significant benefits because of the high cost of transporting and moving mass about in space. An approach to this problem is beaming the power from a point where the massiveness of the power plant is not such a major concern. The viability of such an approach was already investigated. Efficient microwave power beam transmission at 2.45 GHz was demonstrated over short range. Higher frequencies are desired for efficient transmission over several hundred or thousand kilometers in space. Superconducting DC-RF conversion as well as RF-DC conversion offers exciting possibilities. Multivoltage power conditioning for multicavity high power RF tubes could be eliminated since only low voltages are required for Josephson junctions. Small, high efficiency receivers may be possible using the reverse Josephson effects. A conceptual receiving antenna design using superconducting devices to determine possible system operating efficiency is assessed. If realized, these preliminary assessments indicate a role for superconducting devices in millimeter and submillimeter free space power transmission systems.

Christian, Jose L., Jr.↗
NASA NTRS1987

Determination of cloud ice water content and geometrical thickness using microwave and infrared radiometric measurements

Cloud ice water content and cloud geometrical thickness have been determined using a combination of near-infrared, thermal infrared and thermal microwave radiometric measurements. The radiometric measurements are from a Multispectral Cloud Radiometer, which has seven channels ranging from visible to thermal infrared, and an Advanced Microwave Moisture Sounder, which has four channels ranging from 90 to 183 GHz. Studies indicate that the microwave brightness temperatures depend not only on the amount of ice water content but also on the vertical distribution of ice water content. Studies also show that the low brightness temperature at 92 GHz for large ice water content is due to cloud reflection which reflects most of the irradiance incident at the cloud base downward. Therefore the 92 GHz channel detects a low brightness temperature at the cloud top.

Wu, Man-Li C.↗
NASA NTRS1987

Two stage dual gate MESFET monolithic gain control amplifier for Ka-band

A monolithic two stage gain control amplifier has been developed using submicron gate length dual gate MESFETs fabricated on ion implanted material. The amplifier has a gain of 12 dB at 30 GHz with a gain control range of over 30 dB. This ion implanted monolithic IC is readily integrable with other phased array receiver functions such as low noise amplifiers and phase shifters.

Sokolov, V.↗