Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “DE”

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.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 523 records · Page 29
All sourcesNASA NTRSDOE OSTI
NASA NTRS1987

Joule heating in the mesosphere and thermosphere during the July 13, 1982, solar proton event

The solar proton event of July 13, 1982 produced considerable ionization in the polar-cap mesosphere. Energetic solar proton fluxes were measured by the NOAA-6 satellite. The DE-2 satellite measured the low-energy electrons, the ion drift velocity, and other atmospheric and ionospheric properties during the event in the region of the measured maximum electric field (189 mV/m at 2215 UT near 60 deg N), a Joule heating rate of 1-3 K/day is calculated between 70 and 80 km, exceeding the heating due to ozone absorption at noon in the summer hemisphere in that altitude range. The Joule heating rate above 90 km greatly exceeded 20 K/day. The calculated height-integrated Joule heating rate above 100 km in the same region exceeded 400 ergs/sq cm sec, and DE-2 near 350 km measured neutral winds of nearly 1000 m/s and neutral gas temperatures of over 2000 K. The overall ionospheric structure calculated below the DE-2 satellite is described.

Roble, R. G.↗
NASA NTRS1987

Satellite observations of new particle and field signatures associated with SAR arc field lines at magnetospheric heights

Enhancements in thermal ion densities, an oxygen dominated ring current at energies below 17 keV, and invariant latitude-limited bands of intense ELF hiss have been discovered on Stable Auroral Red (SAR) arc field lines at magnetospheric heights. These new signatures were revealed by an examination of 31 coordinated data sets taken simultaneously at magnetospheric and ionospheric heights by the De-1 and -2 satellites during SAR arc traversals within the period September 1981 through April 1982. Data sets from DE-2, for the first time, provide information on the location of a SAR arc (determined by the F region electron temperature enhancement) during the nearly simultaneous passage of these field lines by DE-1 in the magnetosphere. These new high altitude signatures are examined in the context of possible magnetospheric SAR arc energy source mechanisms.

Kozyra, J. U.↗
NASA NTRS1988

On the relationship between dynamics of the polar thermosphere and morphology of the aurora - Global-scale observations from Dynamics Explorers 1 and 2

The effect of the neutral-air circulation in the high-latitude F region on the spatial distribution of the aurora is investigated on the basis of simultaneous global-scale auroral images and neutral-wind vectors obtained over the northern polar cap by the DE 1 and DE 2 satellites in December 1981. The results are presented graphically, along with DE 2 data on the composition, ion densities, and cross-track ion drift of the neutral winds and ISEE-3 IMF measurements, and analyzed. It is found that the large-scale features of the neutral circulation follow the substorm-driven expansion and contraction of the auroral oval, and that the drag effect from ions convecting sunward extends to much lower latitudes and has a more complex morphology than that predicted by GCMs. A number of asymmetries in the flow patterns are considered in detail.

Killeen, T. L.↗
NASA NTRS1988

Dynamics Explorer guest investigator

The research has focused on using the SAI auroral images as a high resolution auroral precipitation input to the USU global scale ionospheric model. From the global scale modeling viewpoint, these images offer unique spatial and temporal resolution since all prior studies have used empirical auroral models. These latter models are devoid of storm, substorm, or discrete oval features. The research focused on the problems in converting images to energy flux; using LAPU data to calibrate these energy fluxes; using the USU Time Dependent Ionospheric Model (TDIM) to look at the ionospheric consequences of this structure; and then using DE-2 in-situ observations to compare with the TDIM ionospheric parameters. In carrying out these studies, several additional investigations cropped up which were pursued to help meet the overall goals. The foremost difficulty in carrying out the TDIM modeling in conjunction with the high resolution DE auroral model was that of defining an appropriate ionospheric convection pattern. Under northward conditions this pattern is very complex. In order to study Theta aurora or in general northward IMF conditions, a new model was required. Hence, a study was completed to supply this new model to drive the TDIM as a function of the IMF. With the DE auroral model having adequate resolution to show structure on the 100's of km and all model electric fields being devoid of such structure, an investigation was pursued to find out the effects of structures in the electric field on the F-region.

Sojka, J. J.↗
NASA NTRS1988

Dynamics Explorer 1 SOI images of the Antarctic ozone hole

The Dynamics Explorer (DE) satellite carries an Auroral Imaging Package which contains filters designed for performing backscatter ultraviolet measurements to measure total column ozone in the Earth's middle and lower atmosphere. Measurements are obtained at 317.5 mm (to measure ozone absorption) and 360 nm (to measure scene reflectivity). In October 1985 and 1986, measurements were obtained near apogee of the Antarctic ozone hole. The only other high spatial resolution measurements were obtained from the Nimbus 7 Total Ozone Mapping Spectrometer (TOMS) experiment. In October 1987, the Dynamics Explorer apogee had precessed into the Northern Hemisphere preventing measurements of the ozone hole. However, measurements should be obtained from DE of the ozone hole in both 1988 and 1989. Considering that the Nimbus 7 TOMS instrument has long exceeded its expected lifetime, the DE Spin Scan Ozone Imager (SOI) experiment could easily play a crucial role in studies of the ozone hole over the next few years.

Keating, G. M.↗
NASA NTRS1988

Mapping of auroral kilometric radiation sources to the aurora

Auroral kilometric radiation (AKR) and optical auroral emissions are observed simultaneously using plasma wave instrumentation and auroral imaging photometers carried on the DE 1 spacecraft. The DE 1 plasma wave instrument measures the relative phase of signals from orthogonal electric dipole antennas, and from these measurements, apparent source directions can be determined with a high degree of precision. Wave data are analyzed for several strong AKR events, and source directions are determined for several emission frequencies. By assuming that the AKR originates at cyclotron resonant altitudes, a candidate source field line is identified. When the selected source field line is traced down to auroral altitudes on the concurrent DE 1 auroral image, a striking correspondece between the AKR source field line and localized auroral features is produced. The magnetic mapping study provides strong evidence that AKR sources occur on field lines associated with discrete auroral arcs, and it provides confirmation that AKR is generated near the electron cyclotron frequency.

Huff, R. L.↗
NASA NTRS1988

Thermosphere dynamics - Recent contributions from Dynamics Explorer-2

This paper discusses results obtained during the period between August 1981, and February 1983, by the instruments aboard the Dynamic Explorer-2 (DE-2) mission, with emphasis placed on the data obtained through the direct measurements of thermospheric vector neutral winds and ion drifts. The DE-2 instrumentation used to obtain the vector neutral-wind observations is described together with the information obtained on the dynamics of the thermosphere. Special consideration is given to the theoretical model development and the ongoing data-theory comparative studies. The progress made during the first five years of the DE mission is summarized.

Killeen, T. L.↗
NASA NTRS1989

Remote sensing of evaporite mineral zonation in salt flats (salars)

Compositional zoning within Salar de Atacama and Salar de Llulliallaco has been mapped from Landsat Thematic Mapper (TM) data. The data were enhanced using decorrelation stretching of TM bands 7, 5, and 4, which were considered to possess the majority of the mineralogical information. The resulting 7, 5, 4 (red, green, blue) color composites provide excellent discrimination of evaporite mineral zones within the salar. The interpretation is supported by fieldwork at the Salar de Atacama and spectral considerations. A strong relationship between the mineralogy of a unit and surface roughness was observed in the field, hence there is potential for imaging radar to provide complementary zonal data.

Chapman, J. E.↗
NASA NTRS1989

Modeled F region response to auroral dynamics based upon Dynamics Explorer auroral observations

Auroral images from the Dynamics Explorer 1 (DE 1) scanning auroral imager have been combined with in situ auroral precipitation data from the DE 2 low-altitude plasma instrument, to form a time-dependent global auroral energy flux model. This model has both good time (12 min) and spatial (100 km) resolution compared to that currently available for global-scale ionospheric and thermospheric modeling. The development and comparison of this model with others are discussed. Data from an aurorally active period, November 25, 1981, are presented and used as a case study for this model. Using a global ionospheric model, the effect of the DE auroral model is contrasted with that of a conventional empirical auroral energy flux model. Major differences in the modeled F region ionosphere are predicted from this comparative study.

Sojka, J. J.↗
NASA NTRS1989

Bonner Durchmusterung (Argelander 1859-1862): Documentation for the machine-readable version

The machine-readable version of the catalog, as it is currently being distributed from the Astronomical Data Center, is described. The entire Bonner Durchmusterung (BD) was computerized through the collaborative efforts of the Centre de Donnees Astronomiques de Strasbourg, l'Observatoire de Nice, and the Astronomical Data Center at the NASA/Goddard Space Flight Center. All corrigenda published in the original BD volumes were incorporated into the machine file, along with changes published following the 1903 edition. In addition, stars indicated to be missing in published lists and verified by various techniques are flagged so that they can be omitted from computer plotted charts if desired. Stars deleted in the various errata lists were similarly flagged, while those with revised data are flagged and listed in a separate table.

Warren, Wayne H., Jr.↗
NASA NTRS1991

The computation of C-C and N-N bond dissociation energies for singly, doubly, and triply bonded systems

The bond dissociation energies (De) of C2H2, C2H4, C2H6, N2, N2H2, and N2H4 are studied at various levels of correlation treatment. The convergence of De with respect to the one-particle basis is studied at the single-reference modified coupled-pair-functional (MCPF)level. At all levels of correlation treatment, the errors in the bond dissociation energies increase with the degree of multiple bond character. The multireference configuration-interaction (MRCI) De values, corrected for an estimate of higher excitations, are in excellent agreement with those determined using the size-extensive averaged-coupled-pair-functional (ACPF) method. The full-valence complete-active-space self-consistent-field (CASSCF)/MRCI calculations are reproduced very well by MRCI calculations based on a CASSCF calculation that includes in the active space only those electrons involved in the C-C or N-N bonds.

Langhoff, Stephen R.↗
NASA NTRS1992

Ionospheric simulation compared with Dynamics Explorer observations for November 22, 1981

The present study uses an extensive DE-2 data base to both constrain inputs to a time-dependent ionospheric model (TDIM) for a simulation of the ionosphere and then check the simulated densities. The investigation was carried out for both a quiet period and a substorm period. The quiet-day study produced very good agreement between modeled and observed electron densities in the topside ionosphere with two significant exceptions: First, across the polar region the DE-2 LANG densities showed fine structure in addition to the overall regional density morphology. Second, a surprising discrepancy arose in the presunrise and midlatitude trough. The TDIM densities were an order of magnitude lower than those observed by DE-2. The substorm study showed remarkably good agreement with the observed densities.

Sojka, J. J.↗
NASA NTRS1992

An experimental investigation of thermospheric structure near an auroral arc

The paper compares observations of thermospheric parameters, made from DE-2 spacecraft during three successive orbital crossings of a quiescent dusk sector auroral arc, with the predictions of three fine-grid auroral arc models. DE-2 measured the ion and neutral window, electron and neutral temperatures, neutral composition, and energetic auroral electron spectra (5 eV to 32 keV) at about 320 km altitude. The DE-2 composition measurements showed a local increase of the N2/O ratio in the arc, which is interpreted to be a result of the upward motion of N2-rich air. A reduction in the measured neutral temperature of about 100 K in the arc, relative to temperatures on either side, was found for all three arc crossings. Of the three theoretical models examined, only one shows a tendency for the neutral thermospheric temperature to drop in the auroral arc, and the decrease is significantly less than the observed temperature change.

Eastes, R. W.↗
NASA NTRS1992

Remote-sensing observations of F-region ion drift velocities using Dynamics Explorer-2 Doppler measurements of the O+(2P) 732.0 nm emission

Limb-scan observations of Doppler line profiles from the O+(2P) 732.0 nm emission at F-region altitudes, made with the Fabry-Perot interferometer (FPI) on the Dynamics Explorer-2 (DE-2) spacecraft, have been analyzed to provide measurements of the meridional component of the ion convection velocity along the instrument line-of-sight. The initial DE-2 results presented here demonstrate the first spaceborne use of the remote-sensing Doppler technique for measurements of ionospheric convection. The FPI meridional ion drift measurements have been compared with nearly simultaneous in situ ion drift measurements from the Retarding Potential Analyzer on DE 2. Once allowance is made for the temporal lag between the in situ and remote measurements, the results from the two techniques are in good agreement. The results of a simulation study demonstrate that the spaceborne interferometric technique has future utility for 2D imaging of the quasi-instantaneous ion convection pattern.

Carr, S. S.↗
NASA NTRS1992

North American Fuzzy Logic Processing Society (NAFIPS 1992), volume 1

This document contains papers presented at the NAFIPS '92 North American Fuzzy Information Processing Society Conference. More than 75 papers were presented at this Conference, which was sponsored by NAFIPS in cooperation with NASA, the Instituto Tecnologico de Morelia, the Indian Society for Fuzzy Mathematics and Information Processing (ISFUMIP), the Instituto Tecnologico de Estudios Superiores de Monterrey (ITESM), the International Fuzzy Systems Association (IFSA), the Japan Society for Fuzzy Theory and Systems, and the Microelectronics and Computer Technology Corporation (MCC). The fuzzy set theory has led to a large number of diverse applications. Recently, interesting applications have been developed which involve the integration of fuzzy systems with adaptive processes such as neural networks and genetic algorithms. NAFIPS '92 was directed toward the advancement, commercialization, and engineering development of these technologies.

Villarreal, James A.↗
NASA NTRS1992

North American Fuzzy Logic Processing Society (NAFIPS 1992), volume 2

This document contains papers presented at the NAFIPS '92 North American Fuzzy Information Processing Society Conference. More than 75 papers were presented at this Conference, which was sponsored by NAFIPS in cooperation with NASA, the Instituto Tecnologico de Morelia, the Indian Society for Fuzzy Mathematics and Information Processing (ISFUMIP), the Instituto Tecnologico de Estudios Superiores de Monterrey (ITESM), the International Fuzzy Systems Association (IFSA), the Japan Society for Fuzzy Theory and Systems, and the Microelectronics and Computer Technology Corporation (MCC). The fuzzy set theory has led to a large number of diverse applications. Recently, interesting applications have been developed which involve the integration of fuzzy systems with adaptive processes such a neural networks and genetic algorithms. NAFIPS '92 was directed toward the advancement, commercialization, and engineering development of these technologies.

Villarreal, James A.↗
NASA NTRS1993

Signal processing of aircraft flyover noise

A detailed analysis of signal processing concerns for measuring aircraft flyover noise is presented. Development of a de-Dopplerization scheme for both corrected time history and spectral data is discussed along with an analysis of motion effects on measured spectra. A computer code was written to implement the de-Dopplerization scheme. Input to the code is the aircraft position data and the pressure time histories. To facilitate ensemble averaging, a level uniform flyover is considered in the study, but the code can accept more general flight profiles. The effects of spectral smearing and its removal are discussed. Using test data acquired from an XV-15 tilt-rotor flyover, comparisons are made between the measured and corrected spectra. Frequency shifts are accurately accounted for by the de-Dopplerization procedure. It is shown that by correcting for spherical spreading and Doppler amplitude, along with frequency, can give some idea about noise source directivity. The analysis indicated that smearing increases with frequency and is more severe on approach than recession.

Kelly, J. J.↗
NASA NTRS1991

Mid- and high-latitude total ozone observations from over three earth radii measured from Dynamics Explorer I

Column ozone measurements obtained from a Spin-scan Ozone Imager (SOI) aboard the Dynamics Explorer I (DE-I) satellite are discussed. The orbital geometry has many features similar to the Molniya satellite orbits. The ozone imagery obtained from DE-I are unique in being synoptic views of a region of continental scale for a period of a few hours. A brief description of the instrument, data, and orbit is followed by a discussion of some applications of DE-I data and the potential usefulness of an ozone imager aboard a satellite in a Molniya-type orbit.

Reynolds, Nathaniel D.↗