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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 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
NASA NTRS1980

The influence of NO and ClO variations at twilight on the interpretation of solar occultation measurements

The influence of short lived photochemically produced species on solar occultation measurements of ClO and NO was examined. Time varying altitude profiles of ClO and NO were calculated with a time dependent photochemical model to simulate the distribution of these species during a solar occultation measurement. These distributions were subsequently used to calculate simulated radiances for various tangent paths from which mixing ratios were inferred with a conventional technique that assumes spherical symmetry. These results show that neglecting the variation of ClO in the retrieval process produces less than a 10 percent error between the true and inverted profile for both sunrise and sunset above 18 km. For NO, errors are less than 10 percent for tangent altitudes above about 35 km for sunrise and sunset; at lower altitudes, the error increases, approaching 100 percent at altitudes near 25 km. the results also show that average inhomogeneity factors, which measure the concentration variation along the tangent path and which can be calculated from a photochemical model, can indicate which species require more careful data analysis.

Boughner, R.↗
NASA NTRS1980

Interpretation of laser/multi-sensor data for short range terrain modeling and hazard detection

A terrain modeling algorithm that would reconstruct the sensed ground images formed by the triangulation scheme, and classify as unsafe any terrain feature that would pose a hazard to a roving vehicle is described. This modeler greatly reduces quantization errors inherent in a laser/sensing system through the use of a thinning algorithm. Dual filters are employed to separate terrain steps from the general landscape, simplifying the analysis of terrain features. A crosspath analysis is utilized to detect and avoid obstacles that would adversely affect the roll of the vehicle. Computer simulations of the rover on various terrains examine the performance of the modeler.

Messing, B. S.↗
NASA NTRS1979

Apollo 12 feldspathic basalts 12031, 12038 and 12072 - Petrology, comparison and interpretations

The paper presents the petrology of Apollo 12 feldspathic basalts. Modal and chemical data indicate that basalts 12072, 12038, and 12031 cannot be related to the other Apollo rock types; 12072 contains phenocrysts of olivine and pigeonite, 12038 is a multiply saturated equigranular basalt, and 12031 is a coarse-grained rock with granular to graphic intergrowths of pyroxene and plagioclase. The bulk compositions indicate that these basalts could not have been derived from the Apollo 12 olivine or ilmenite basalts by crystal-liquid fractionation, and their petrologic similarities suggest that they were produced in the same or similar source regions.

Beaty, D. W.↗
NASA NTRS1980

Seasonal variations in high-latitude ozone and metastable molecular oxygen emissions - A theoretical interpretation

Comparison of photochemical calculations of atmospheric ozone between 40 and 55 km with measurements from a satellite-borne remote sensor shows agreement in the high-latitude summer hemisphere. However, in the sunlit high-latitude winter, the available data imply either a smaller water vapor mixing ratio than generally accepted or a temperature 15 - 20 K colder than contained in published model atmospheres. As with the ozone data the infrared emission in winter implies an odd oxygen loss rate smaller than predicted on the basis of standard water vapor and temperature models. The magnitude of the 1.27 micron signals and their consistency with upper stratospheric ozone data cast doubt on the large mesospheric ozone abundances deduced in independent experiments.

Frederick, J. E.↗
NASA NTRS1980

Stereo radar for mapping and interpretation

The use of terrain imaging radar to extract elevation information by stereo viewing and measurement is discussed. Either a three dimensional visual model or elevation measurements may be obtained by simultaneous viewing or differential measurement of images obtained by a side-looking radar from two different flightpaths. Expressions describing radar image geometry, model vertical exaggeration, and stereo measurement accuracy are derived. The dependence of the exaggeration and accuracy on system parameters and key system errors is derived, discussed, and illustrated by application to several airborne and spaceborne systems and system concepts, and the results of some preliminary measurements of imagery from two airborne and one spaceborne system are given.

Graham, L.↗
NASA NTRS1980

New interpretations of shock-associated noise with and without screech

Anomalous trends in present convergent nozzle (Mach 1) shock associated noise analyses and predictions, with particular emphasis on the roles of screech and jet temperature, are discussed. Experimentally measured values of shock associated noise are used to reassess data trends, including both frequency and sound pressure level. The data used includes model-scale nozzles, varying in nominal diameter from 5 cm to 13 cm, and full scale engine nozzles up to 48 cm. All data were obtained at static conditions. From this reassessment of the measured data, new empirical methods for the prediction of shock associated noise are developed. Separate procedures are presented for screech free and screech contaminated shock associated noise. In the present approach, shock associated noise spectra are developed from considerations that include the peak sound pressure level and its frequency, the low frequency sound pressure level slope, and the high frequency sound pressure level slope or roll-off; the latter is shown to vary with directivity angle.

Vonglahn, U.↗
NASA NTRS1980

The reduction, verification and interpretation of Magsat magnetic data over Canada

The primary concern of this investigation is to detect and study variations in the magnetic field originating in the solid Earth, as measured by Magsat. Most of this field originates in the core, but an important part of the field is of lithospheric origin. Magnetic anomalies of lithospheric origin are weak at Magsat altitudes (20 to 30 nT at most), and they can easily be masked by much larger effects caused by field aligned and other currents at high latitudes. Most of Canada lies under the influence of ionospheric currents in the auroral zone and polar cap. Therefore, before Magsat data had become available, but after the October 30, 1979 launch, criteria were developed for selecting times when subsets of potentially usable Magsat data could be expected. Subsequently, as Magsat data became available, these critieria were applied.

Coles, R. L.↗
NASA NTRS1981

RAWINPROC: Computer program for decommutating, interpreting, and interpolating Rawinsonde meteorological balloon sounding data

The FORTRAN computer program RAWINPROC accepts output from NASA Wallops computer program METPASS1; and produces input for NASA computer program 3.0.0700 (ECC-PRD). The three parts together form a software system for the completely automatic reduction of standard RAWINSONDE sounding data. RAWINPROC pre-edits the 0.1-second data, including time-of-day, azimuth, elevation, and sonde-modulated tone frequency, condenses the data according to successive dwells of the tone frequency, decommutates the condensed data into the proper channels (temperature, relative humidity, high and low references), determines the running baroswitch contact number and computes the associated pressure altitudes, and interpolates the data appropriate for input to ACC-PRD.

Staffanson, F. L.↗
NASA NTRS1981

IUE observations and interpretation of the symbiotic star RW Hya

The IUE observations of the high excitation symbiotic star RW Hya (gM2 + pec) are discussed. Analysis of the intense UV continuum observed between 1100 A to 2000 A suggests this star is a binary system in which the secondary is identified as a hot subdwarf with T sub eff being approximately 100,000 K. A distance to the system of 1000 pc is deduced. The UV spectrum consists of mainly semiforbidden and allowed transition lines of which the CIV (1548 A, 1550 A) emission lines are particularly strong, and UV continuum at both shorter and longer wavelengths. Strong forbidden lines seem to be absent suggesting the presence of a nebula of high densities. Tidal interaction between the red giant primary and the hot subdwarf is suggested as a likely means to form the observed nebula. RW Hya is suggested as a possible source of soft X-ray emission from material accreting onto the surface of the hot subdwarf. Detection of such emission with HEAO-B would give information if this accretion is taking place via Roche lobe overlow or via capture from a stellar wind emitted by the primary. A general discussion of elemental and ionic abundances in the nebula is also presented.

Kafatos, M.↗
NASA NTRS1981

Solar flare observations and their interpretations

A solar flare has a characteristic spatial extent of 10,000 to 100,000 km. It develops rapidly, with a characteristic time scale of 100 to 1000 s but its manifestations can be observed for hours after onset. A solar flare is the source of highly energetic particles with energies that extend into the GeV range; it produces copious amounts of electromagnetic radiation from gamma-rays to wavelengths of 10 km; and it produces violent magnetohydrodynamic phenomena such as shocks and fast mass ejections. The three basic phases of a flare are described and are: the precursor (preflare) phase, lasting for minutes to hours; the flash phase, lasting for 1 to 5 minutes; and the main (gradual) phase, lasting, on occasion, for hours.

Brown, J. C.↗
NASA NTRS1980

Weather analysis and interpretation procedures developed for the US/Canada wheat and barley exploratory experiment

Procedures and techniques for providing analyses of meteorological conditions at segments during the growing season were developed for the U.S./Canada Wheat and Barley Exploratory Experiment. The main product and analysis tool is the segment-level climagraph which depicts temporally meteorological variables for the current year compared with climatological normals. The variable values for the segment are estimates derived through objective analysis of values obtained at first-order station in the region. The procedures and products documented represent a baseline for future Foreign Commodity Production Forecasting experiments.

Trenchard, M. H.↗
NASA NTRS1980

The H I Lyman continuum in solar prominences and its interpretation in the presence of inhomogeneities

Observations of the H I Lyman continuum are presented for nine hedgerow prominences observed at the limb with the Harvard EUV spectrometer on Skylab. Methods of analysis for both the continuum emission and absorption are developed for two contrasting models for the prominence fine structure, namely multiple resolved slabs, and multiple unresolved cylindrical threads. The absorption data set a lower limit on the total optical thickness at 912 A and on the number of structures in the line of sight. The emission data yield a mean electron temperature of 7524 + or - 739 K and a mean brightness temperature of 6316 + or - 75 K. Taken together the emission and absorption data set firm constraints on the ionization, density, and fractional volume.

Orrall, F. Q.↗
NASA NTRS1980

The effect of directional radiation models on the interpretation of earth radiation budget measurements

A parameter estimation technique is presented to estimate the radiative flux density distribution over the earth from a set of radiometer measurements at satellite altitude. The technique analyzes measurements from a wide field of view, horizon to horizon, nadir pointing sensor with a mathematical technique to derive the radiative flux density estimates at the top of the atmosphere for resolution elements smaller than the sensor field of view. A computer simulation of the data analysis technique is presented for both earth-emitted and reflected radiation. The errors resulting from the assumed directional radiation model, spatial model and random measurement error have little effect on the global mean radiation. Zonal estimates were found to be more sensitive to the spatial model than to the directional radiation model. Results from analyzing medium field of view measurements showed a much greater sensitivity to the directional radiation model even on a global scale.

Green, R. N.↗
NASA NTRS1980

New interpretations of shock-associated noise with and without screech

Anomalous trends in present convergent nozzle (Mach 1) shock-associated noise analyses and predictions, with particular emphasis on the roles of screech and jet temperature, are discussed. Experimentally measured values of shock-associated noise are used to reassess data trends, including both frequency and sound pressure level. The data used includes model-scale nozzles, varying in nominal diameter from 5 cm to 13 cm, and full-scale engine nozzles up to 48 cm. All data were obtained at static conditions. From this reassessment of the measured data, new empirical methods for the prediction of shock-associated noise are developed. Separate procedures are presented for screech-free and screech-contaminated shock-associated noise. In the present approach, shock-associated noise spectra are developed from considerations that include the peak sound pressure level and its frequency, the low frequency sound pressure level slope, and the high frequency sound pressure level slope or roll-off; the latter is shown to vary with directivity angle.

Von Glahn, U.↗
NASA NTRS1980

Radar image enhancement and simulation as an aid to interpretation and training

Greatly increased activity in the field of radar image applications in the coming years demands that techniques of radar image analysis, enhancement, and simulation be developed now. Since the statistical nature of radar imagery differs from that of photographic imagery, one finds that the required digital image processing algorithms (e.g., for improved viewing and feature extraction) differ from those currently existing. This paper addresses these problems and discusses work at the Remote Sensing Laboratory in image simulation and processing, especially for systems comparable to the formerly operational SEASAT synthetic aperture radar.

Frost, V. S.↗
NASA NTRS1980

Net radiation in the atmosphere of Venus - Measurements and interpretation

Aerodynamic testing of the Pioneer Venus small probe net flux radiometer (SNFR) has led to a better understanding of transient errors in the net flux measurements immediately following deployment. Corrections to the net flux profiles in this region produce profiles that are reasonably consistent with constraints imposed by ground-based and orbiter results for fluxes above the atmosphere. The tests raised questions about possible steady state errors associated with the changing atmospheric temperature encountered as the probes descended. However, the lack of sensor-to-sensor variability of the transient error (caused by a newly discovered flow-through mechanism) suggests that any related errors discovered by future testing will be correctable and will not alter the conclusions that net fluxes in the lower atmosphere vary considerably with location and are relatively large at the north and night probe sites.

Suomi, V. E.↗