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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 1,279 records · Page 71
All sourcesNASA NTRSDOE OSTI
NASA NTRS1978

NASA automatic subject analysis technique for extracting retrievable multi-terms (NASA TERM) system

Current methods for information processing and retrieval used at the NASA Scientific and Technical Information Facility are reviewed. A more cost effective computer aided indexing system is proposed which automatically generates print terms (phrases) from the natural text. Satisfactory print terms can be generated in a primarily automatic manner to produce a thesaurus (NASA TERMS) which extends all the mappings presently applied by indexers, specifies the worth of each posting term in the thesaurus, and indicates the areas of use of the thesaurus entry phrase. These print terms enable the computer to determine which of several terms in a hierarchy is desirable and to differentiate ambiguous terms. Steps in the NASA TERMS algorithm are discussed and the processing of surrogate entry phrases is demonstrated using four previously manually indexed STAR abstracts for comparison. The simulation shows phrase isolation, text phrase reduction, NASA terms selection, and RECON display.

Kirschbaum, J.↗
NASA NTRS1977

A single field of view method for retrieving tropospheric temperature profiles from cloud-contaminated radiance data

The paper presents a method for retrieving single field of view tropospheric temperature profiles directly from cloud-contaminated radiance data through the use of auxiliary data such as observed shelter temperatures and estimated cloud-top height. A model was formulated to calculate cloud parameters for use with the radiative transport equation at an estimated cloud-top level. The cloud and temperature data are used in conjunction with real and simulated radiance data from NOAA satellites.

Hodges, D. B.↗
NASA NTRS1977

On the effect of surface emissivity on temperature retrievals

The paper is concerned with errors in temperature retrieval caused by incorrectly assuming that surface emissivity is equal to unity. An error equation that applies to present-day atmospheric temperature sounders is derived, and the bias errors resulting from various emissivity discrepancies are calculated. A model of downward flux is presented and used to determine the effective downward flux. In the 3.7-micron region of the spectrum, emissivities of 0.6 to 0.9 have been observed over land. At a surface temperature of 290 K, if the true emissivity is 0.6 and unit emissivity is assumed, the error would be approximately 11 C. In the 11-micron region, the maximum deviation of the surface emissivity from unity was 0.05.

Kornfield, J.↗
NASA NTRS1977

A summary of Nimbus-6 temperature retrieval accuracy statistics for DST-5 and DST-6

Statistics compiled from Nimbus-6 temperature retrievals processed during the 18 August-4 September 1975 DST-5, and the 1 February-4 March 1976 DST-6 are addressed. All statistics were compiled from samples of colocated satellite sounding and radiosonde measurements. The colocation window is 222 km in space and 6 hours in time.

Hayden, C. M.↗
NASA NTRS1979

An algorithm for retrieval of ocean surface and atmospheric parameters from the observations of the scanning multichannel microwave radiometer (SMMR)

A formalism was developed which can be used to interpret the data in terms of sea surface temperature, sea surface wind speed, and the atmospheric overburden of water vapor and liquid water. It was shown with reasonable instrumental performance assumptions, these parameters could be derived to useful accuracies. Although the algorithms were not derived for use in rain, it is shown that, at least, token rain rates can be tolerated without invalidating the retrieved geophysical parameters.

Wilheit, T. T.↗
NASA NTRS1979

Round-Trip Missions to Low-Delta-V Asteroids and Implications for Material Retrieval

Low-delta-V asteroids are to be found among those which have perihelia near 1 AU. From the 50 known asteroids with perihelia less than 1.5 AU, 10 candidates for asteroid retrieval missions were selected on the basis of low eccentricity and inclination. To estimate the ranges of orbital elements for which capture in earth orbit may be feasible, a survey was made of 180 deg transfer from a set of orbits having elements near those of the earth to the earth. For 2 of the 10 low-delta-V asteroids and for an additional one with elements more earth-like than any yet known, direct ballistic round trips in the 1980's were computed. A stay time of several months at the asteroid was used. The results show that the total delta V, including that for rendezvous with earth upon return, for the known asteroids is above 14 km/sec. But if asteroids are found similar to the strawman considered, the total delta V could be as low as 10 km/sec.

David F Bender↗
NASA NTRS1978

Parameterization of surface temperature retrieval for remote sensing experiments

The paper describes a parameterization procedure for determining the actual surface temperature from the effective brightness temperature measured radiometrically in the 11-micron window region. The algorithm permits computation of the atmospheric correction without performing detailed radiative transfer calculations, and corrections for atmospheric water vapor and for variations of surface emittance are explained. The parameterization is based on model calculations performed with a line-by-line radiative transfer program, and the sensitivity of the retrieved surface temperature to uncertainties concerning the water vapor and the surface emittance is examined.

Tiwari, S. N.↗
NASA NTRS1977

Achievements in optical data storage and retrieval

The present paper deals with the current achievements in two technology efforts, one of which is a wideband holographic recorder which uses multichannel recording of data in the form of holograms on roll film for storage and retrieval of large unit records at hundreds of megabit per second. The second effort involves a system (termed DIGIMEN) which uses binary spot recording on photographic film in the form of microfiche to provide a mass storage capability with automatic computer-controlled random access to stored records. Some potential design improvements are noted.

Nelson, R. H.↗
NASA NTRS1980

BIRP: Software for interactive search and retrieval of image engineering data

Better Image Retrieval Programs (BIRP), a set of programs to interactively sort through and to display a database, such as engineering data for images acquired by spacecraft is described. An overview of the philosophy of BIRP design, the structure of BIRP data files, and examples that illustrate the capabilities of the software are provided.

Arvidson, R. E.↗
NASA NTRS1980

Friction evaluation of unpaved, gypsum-surface runways at Northrup Strip, White Sands Missile Range, in support of Space Shuttle Orbiter landing and retrieval operations

Friction measurement results obtained on the gypsum surface runways at Northrup Strip, White Sands Missile Range, N. M., using an instrumented tire test vehicle and a diagonal braked vehicle, are presented. These runways were prepared to serve as backup landing and retrieval sites to the primary sites located at Dryden Flight Research Center for shuttle orbiter during initial test flights. Similar friction data obtained on paved and other unpaved surfaces was shown for comparison and to indicate that the friction capability measured on the dry gypsum surface runways is sufficient for operations with the shuttle orbiter and the Boeing 747 aircraft. Based on these ground vehicle friction measurements, estimates of shuttle orbiter and aircraft tire friction performance are presented and discussed. General observations concerning the gypsum surface characteristics are also included and several recommendations are made for improving and maintaining adequate surface friction capabilities prior to the first shuttle orbiter landing.

Yager, T. J.↗
NASA NTRS1980

Windfield retrieval from Doppler lidar observations

An approach to the retrieval of a vector wind field from Doppler lidar observations is developed in general terms. The field of radial velocity measurements from each look angle is modeled by a smooth surface, the parameters of the model being determined from the data by least squares techniques. The vector wind field and higher-order fields are obtained from the two modeled surfaces. Estimated measurement errors are taken into account, and error estimates are available for all output data sets.

Lee, R. W.↗
NASA NTRS1979

Temperature profile retrievals with extended Kalman-Bucy filters

The Extended Kalman-Bucy Filter is a powerful technique for estimating non-stationary random parameters in situations where the received signal is a noisy non-linear function of those parameters. A practical causal filter for retrieving atmospheric temperature profiles from radiances observed at a single scan angle by the Scanning Microwave Spectrometer (SCAMS) carried on the Nimbus 6 satellite typically shows approximately a 10-30% reduction in rms error about the mean at almost all levels below 70 mb when compared with a regression inversion.

Ledsham, W. H.↗
NASA NTRS1980

An algorithm for retrieval of ocean surface and atmospheric parameters from the observations of the scanning multichannel microwave radiometer

The scanning multichannel microwave radiometer is a five-frequency (6.6, 10.7, 18, 21, and 37 GHz), dual-polarized microwave radiometer, which was launched in two separate satellites, Nimbus 7 and Seasat, in 1978. A formalism is developed which can be used to interpret the data in terms of sea surface temperature, sea surface wind speed, and the atmospheric content of water vapor and liquid water. It is shown with reasonable instrumental performance assumptions that these parameters can be derived to useful accuracies. Although the algorithms are not derived for use in rain, it is shown that at least token rain rates can be tolerated without invalidating the retrieved geophysical parameters.

Wilheit, T. T.↗
NASA NTRS1980

Windfield retrieval from Doppler lidar observations

An approach to the retrieval of a vector wind field from Doppler lidar observations is developed in general terms. The field of radial velocity measurements from each look angle is modeled by a smooth surface, the parameters of the model being determined from the data by least squares techniques. The vector wind field and higher order fields are obtained from the two modeled surfaces. Estimated measurement errors are taken into account, and error estimates are available for all output data sets.

Lee, R. W.↗
NASA NTRS1980

Evaluation of atmospheric density models and preliminary functional specifications for the Langley Atmospheric Information Retrieval System (LAIRS)

This document presents the results of an extensive survey and comparative evaluation of current atmosphere and wind models for inclusion in the Langley Atmospheric Information Retrieval System (LAIRS). It includes recommended models for use in LAIRS, estimated accuracies for the recommended models, and functional specifications for the development of LAIRS.

Lee, T.↗
NASA NTRS1980

Role of multiple scattering in ozone profile retrieval from satellite measurements in the ultraviolet

The retrieval of the ozone profile from satellite ultraviolet measurements can be extended to greater depths when multiple scattering is taken into account. The sensitivity of the multiple-scattered wavelength radiances to geophysical variables are discussed and results of profile inversions of Nimbus 4 backscatter ultraviolet data for coincident ground-truth measurements with and without multiple scattering are presented.

Taylor, S. L.↗
NASA NTRS1981

Retrieval and use of high-resolution moisture and stability fields from Nimbus 6 HIRS radiances in pre-convective situations

A moisture-temperature retrieval scheme was developed for lower-tropospheric analysis and forecasting parameters from the Nimbus 6 High-resolution Infrared Radiation Sounder, in a study of convective development on the Great Plains of the U.S. on four case study days in August 1975. Dew points and temperatures, along with such secondary parameters as total precipitate water and static stability indices, were derived and analyzed at a horizontal resolution of up to 30 km on the four days. Convective development beginning 2.0-2.5 hours after the satellite pass at local noon was found to correlate well with local moisture and instability maxima seen in the satellite-derived analyses. A statistical structure analysis of the satellite-derived parameters gave the highest signal-to-noise values for the moisture and stability parameters, while the temperature parameters showed much lower signal-to-noise content.

Hillger, D. W.↗