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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS1985

Intercomparison of satellite ozone profile measurements

Ozone profile data are intercompared with those from the LIMS and SBUV flown on Nimbus 7, SAGE flown on Atmospheric Explorer Mission 2, and the Ultraviolet and Infrared Spectrometers flown on the SME. Ozone data were derived from the measurements with independently derived processing algorithms. The data cover different time periods and have different spatial and temporal resolutions. The similarities and differences between the individual data sets are determined with effort focused on directly comparing the spacecraft data sets in the form of individual profiles, zonal mean profiles and global analyses. Comparisons with ground data from balloons and Umkehr stations are made.

Fleig, A. J.↗
NASA NTRS1986

Plume characteristics of single-stream and dual-flow conventional and inverted-profile nozzles at equal thrust

The plume velocity and temperature decay rates of single-stream, conventional dual-flow and inverted-profile dual-flow nozzles are compared at equal values of ideal thrust over a wide range of flow conditions. The comparisons are made in terms of constant velocity and temperature contour maps. The results show that both dual-flow nozzle types have much greater plume velocity and temperature decay rates than those of equivalent thrust single-stream nozzles when the respective secondary flows were at ambient temperature. With hot secondary flows, the inverted-profile dual-flow plumes decayed significantly faster than those of single-stream nozzles; however, the decay rates for the conventional dual-flow streams were about the same as those for the single-stream nozzles. Consequently, with hot secondary flows, the inverted-profile dual-flow plumes decayed much faster than the conventional dual-flow plumes at equal thrust.

Von Glahn, U. H.↗
NASA NTRS1986

Geostationary Operational Environmental Satellite (GOES) mission profile

The GOES mission profile used to achieve geostationary orbit following separation from the Delta launch vehicle is described. The mission profile was constrained by the solid-propellant apogee kick motor which was undersized relative to the spacecraft weight. The resulting deficiency in delivered delta-V had to be made up by the spacecraft hydrazine propulsion system. The mission profile which best utilizes the on-board hydrazine requires that the transfer orbit apogee height be biased 13,800 km above geosynchronous altitude. This maximizes the effectiveness of the apogee motor in performing the plane change necessary to achieve near-equatorial orbit. The highly eccentric drift orbit which results from the apogee motor firing has an average drift rate of 60 deg/day. Circularizing this orbit requires maneuvers designed to achieve geostationary position within a tightly constrained hydrazine allocation. The sequence takes advantage of the orbit changes resulting from attitude maneuvers and combined inplane/out-of-plane maneuvers to achieve hydrazine savings.

Bryant, W. C.↗
NASA NTRS1986

Optimal filtration of the atmospheric parameters profiles

The idea of optimal Marcovian filtration of fluctuating profiles from lidar signals is developed but as applied to a double-frequency sounding which allows the use of large cross sections of elastic scattering and correct separation of the contributions due to aerosol and Rayleigh scatterings from the total lidar return. The filtration efficiency is shown under different conditions of sounding using a computer model. The accuracy of restituted profiles (temperature, pressure, density) is determined by the elements of a posteriori matrix K. The results obtained allow the determination of the lidar power required for providing the necessary accuracy of restitution of the atmospheric parameter profiles at chosen wavelengths of sounding in the ultraviolet and visible range.

Zuev, V. E.↗
NASA NTRS1986

Lower atmospheric temperature profile measurements using a Raman lidar

A Raman lidar system was used to measure the temperature profile of the upper troposphere and lower stratosphere. The system consists of a tripled Nd-YAG laser and a 1.5 meter diameter telescope. Two photomultipliers are used at the output of the telescope to allow for measurements at both the laser wavelength and at the Raman shifted wavelength due to atmospheric nitrogen. The signal from the photomultipliers is recorded as photon counts in 1 microsec bins. The results of a number of laser shots are summed together to provide atmospheric returns which have acceptable signal to noise characteristics. Measurements of the Raman nitrogen return were acquired up to an altitude in excess of 20 km. Temperature profiles were retrieved from the attenuation corrected Raman nitrogen return assuming the atmosphere to be in hydrostatic equilibrium and using the ideal gas law. Retrieved temperature profiles are shown compared with independent temperature measurements.

Melfi, S. H.↗
NASA NTRS1986

Laser heterodyne system for obtaining height profiles of minor species in the atmosphere

An infrared laser heterodyne system for obtaining height profiles of minor constituents of the atmosphere was developed and erected. A brief discription of the system is given. The system consists of a tunable CO2 waveguide laser in the 9 to 11 micrometer band, that is used as a local oscillator and a heliostat that follows the sun and brings in solar radiation, that is mixed with the laser beam in a high speed liquid nitrogen cooled mercury cadmium telluride detector. The detected signal is analysed in a RF spectrum analyser that allows tracing absorption line profiles. Absorption lines of a number of minor constituents in the troposphere and stratosphere, such as O3, NH3, H2O, SO2, ClO, N2O, are in the 9 to 11 micrometer band and overlap with that of CO2 laser range. The experimental system has been made operational and trial observations taken. Current measurements are limited to ozone height profiles. Results are presented.

Jain, S. L.↗
NASA NTRS1986

Wind profiler data in a mesoscale experiment from a meteorological perspective

During May and June of 1985, the Oklahoma-Kansas Preliminary Regional Experiment of STORM-Central (OK PRE-STORM) was carried out, with the major objectives of learning more about mesoscale convective systems (MCSs) and gaining experience in the use of new sensing systems and measurement strategies that will improve the design of STORM-Central. Three 50-MHz wind profilers were employed in a triangular array with sides about 275 km. It is far too soon to report any results of this effort, for it has barely begun. The purpose here is to show some examples of the data, some of the surrounding conventional data, and to discuss some of the issues important to meteorologists in evaluating the contribution of the profiler data. The case of 10 to 11 June 1985, featuring a major squall line system which crossed the dense observing network from northwest to southeast, passing the Liberal site about 2230 GMT/10 June, the McPherson site about 0100 GMT/11 June, and Wichita about 0300 GMT/11 June is discussed. Radar and satellite data show that the system was growing rapidly when it passed Liberal, and was large and mature when it passed through McPherson and Wichita. The radar depiction of the system during this stage is given, with the McPherson site in the intense convective echoes near the leading edge at 01 GMT and in the stratiform precipitation at 03 GMT. The profiler wind data for a 9-hour period encompassing the squall line passage at each site are given.

Zipser, E. J.↗
NASA NTRS1986

Colorado wind profilers

The Wave Propagation Laboratory (WPL) has operated a network of wind profiling radars in Colorado. The current configuration of the network is described. All radars operate continuously and unattended to supply hourly-averaged wind profiles to a central computer in Boulder in real time. The hardware and software changes made to improve reliability are discussed. This research network will continue to be used to provide wind profiles for operational and research meteorologists and the performance of various wavelength systems will be evaluated.

Strauch, R. G.↗
NASA NTRS1986

Wind profiler demonstration system

The National Oceanic and Atmospheric Administration (NOAA) has started procurement of a 30-station demonstration network of Doppler radar wind profilers to be deployed in the central United States by 1989. The purposes of this demonstration network are: (1) to assess the impact of a large wind profiler network on meteorological forecasting; (2) to test wind profiler hardware designed specifically for commercial production and widespread deployment; and (3) to provide wind data for research programs involving weather phenomena in the central United States.

Chadwick, R. B.↗
NASA NTRS1986

Fe II emission line profiles in spectra of high luminosity non-coronal stars

The results of a program to study the winds of noncoronal late-type giant and supergiant stars with IUE are presented. The primary data for this study are profiles, fluxes, and velocities of the Fe II emission lines which occur throughout the 2200 to 3230 A region of the IUE long wavelength spectrographs. The apparent dependence of the Fe II profiles on stellar luminosity (surface gravity) and intrinsic line strength is discussed. The discovery of significant changes in the Fe II profiles in spectra of Gamma Crucis (M3 III), during the period 1978 to 1985, that suggest a substantial change in its outer atmosphere is noted.

Carpenter, Kenneth G.↗
NASA NTRS1986

Comet Halley neutral gas density profile along the Vega 1 trajectory measured by NGE

Data from the Vega 1 permitted the determination of the total neutral gas density profile along the spacecraft trajectory. Discounting small fluctuations, the field ionization source instrument measured a density profile which varied approximately as the inverse radial distance squared. Data from the electron impact ionization instrument yielded a series of calibration points; e.g., the neutral density at 100,000 km is 10,000/cc. The combined data provide a calibrated total density profile, and imply a neutral production rate of 10 to the 30th power molecules/sec.

Curtis, C. C.↗
NASA NTRS1986

QSO emission line profiles from Keplerian cloud ensembles

Quasar broad emission line profile calculations are presented for spherically symmetric ensembles of flattened broad-line clouds in elliptical Keplerian orbits. In general, it is found that high eccentricity monoenergetic orbital ensembles tend to provide more acceptable profiles than low eccentricity monoenergetic ensembles. The investigation of elliptical cloud orbits evolving under the influence of Poynting-Robertson drag or drag from an intercloud media shows that acceptable line profiles naturally result from the decay of initially monoenergetic, high eccentricity ensembles independent of the assumed emission anisotropy, provided the drag is not so great as to cause the immediate capture or disruption of the clouds.

Bradley, S. E.↗
NASA NTRS1986

Solar chromospheric modeling based on submillimeter limb brightness profile

A method of modeling the solar chromosphere is developed, based on submillimeter continuum observations of the solar limb. Submillimeter radiation from the solar limb emanates from the chromosphere in local thermodynamic equilibrium, making it an important chromospheric diagnostic. Also, the use of high-resolution limb profiles allows for atmospheric modeling independent of gravitational hydrostatic equilibrium. The chromospheric model is constructed to match high-resolution solar limb profiles at 30, 50, 100, and 200 microns, determined by an occultation of the solar limb observed from the Kuiper Airborne Observatory during the total solar eclipse of July 31, 1981. This matching is achieved by 'stretching' the solar model atmosphere of Vernazza, Avrett, and Loesser (1981) vertically out of hydrostatic equilibrium, while maintainingn its vertical temperature-optical depth profile.

Hermans, L. M.↗
NASA NTRS1987

Balmer profiles in the geocorona and interstellar space. I - Asymmetries due to fine structure

While the Doppler profiles of Balmer-alpha and -beta are in principle analyzable in order to derive orbital data concerning both escaping and satellite geocoronal particles, interpretations are in practice hampered by a lack of understanding of profile properties apart from such geocoronal features as an asymmetry, caused by the absence of escape velocity-exceeding, downward-directed particles. Attention is accordingly given to the profiles of H atoms which, while emitting radiation from a complete Maxwellian distribution, also exhibit an H-alpha fine structure-generated asymmetry which is a predictable function of the excitation mechanism.

Chamberlain, Joseph W.↗
NASA NTRS1987

Simultaneous measurement of stratospheric O3, H2O, CH4, and N2O profiles from infrared limb thermal emissions

Thermal emission measurements of the earth's stratospheric limb were made with a cryogenically cooled high-resolution Michelson interferometer on a balloon flight launched from Palestine, TX, on Nov. 6, 1984. Infrared spectra for complete limb sequences were obtained over portions of the 700-1940/cm range with an unapodized spectral resolution of 0.03/cm for tangent heights varying from 13 to 39 km. The observed data from 1125 to 1425/cm have been analyzed for simultaneous measurement of O3, H2O, CH4, and N2O profiles. The analysis employs line-by-line and layer-by-layer radiative-transfer calculations, including curvature and refraction effects. The optimum use of geometric and spectral effects is made to obtain sharply peaked weighting functions. Contributions from stratospheric aerosol are included by measuring the light extinction within the window regions of the observed spectra. The retrieved constituent profiles are compared with measurements made with a variety of techniques by other groups. The comparison shows good agreement with the published data for all gases, indicating the capability of retrieving trace gas profiles from high-resolution thermal emission limb measurements.

Abbas, M. M.↗
NASA NTRS1987

Forbidden line and H-alpha profiles in T Tauri star spectra - A probe of anisotropic mass outflows and circumstellar disks

The results of a high-resolution spectroscopic study of 10 T Tauri stars (TTS) and two Herbig emission stars are presented based on red echelle spectra including the lines of forbidden O I 6300 A, forbidden N II 6584 A, forbidden S II 6716, 6731 A, as well as H-alpha. The forbidden lines display a continuous progression of profile types. The velocity structure in the forbidden lines is critically examined and compared to computed line profiles for a number of different wind models. Constant velocity spherical or conical winds fail to reproduce the observed line profiles, which are better explained by a wind with a latitude-dependent velocity field. A prediction of the wind model correlating the velocity of the reversal at H-alpha and the forbidden line velocity structure as a function of the view angle to the star is explored. Estimates of the average densities and sizes for the TTS forbidden emission regions are presented, and mass-loss rates are computed. IRAS far-IR fluxes are used to estimate the disk sizes.

Edwards, Suzan↗
NASA NTRS1987

Soft X-ray line profiles in the impulsive phase of electron-heated solar flares

Using a model of the hydrodynamic response of a flare loop to energy input in the form of a nonthermal electron beam, the predicted line profile of the Ca XIX resonance line at 3.177 A is computed. The results are compared with observations and are shown to generally agree, both qualitatively and quantitatively, with these observations. The model does, however, predict an overall blueshift in the line profile, a result which differs with earlier interpretations of the observations, and which remains to be tested by absolutely calibrated measurements of the Ca XIX spectrum. It is concluded that electron-heated models of solar flares quite naturally predict the observed features in the Ca XIX line profile, without the need to introduce nonthermal motions or an artificial division of the flare plasma into two distinct components, as suggested by previous authors.

Emslie, Gordon A.↗
NASA NTRS1987

Fermi acceleration at shocks with arbitrary velocity profiles

Diffusive particle acceleration in modified shock fronts is considered. A method by means of which to obtain the resulting particle spectrum for an arbitrary flow profile is outlined; this method is based on a reformulation of the transport equation as a nonlinear first-order equation. Besides the shape of the flow profile, the spectral index of particles depends on the Peclet number of the shock. Results are given for some sample profiles.

Schneider, Peter↗