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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 NTRS1975

A feasibility study for the detection of upper atmospheric winds using a ground based laser Doppler velocimeter

A possible measurement program designed to obtain the information requisite to determining the feasibility of airborne and/or satellite-borne LDV (Laser Doppler Velocimeter) systems is discussed. Measurements made from the ground are favored over an airborne measurement as far as for the purpose of determining feasibility is concerned. The expected signal strengths for scattering at various altitude and elevation angles are examined; it appears that both molecular absorption and ambient turbulence degrade the signal at low elevation angles and effectively constrain the ground based measurement of elevation angles exceeding a critical value. The nature of the wind shear and turbulence to be expected are treated from a linear hydrodynamic model - a mountain lee wave model. The spatial and temporal correlation distances establish requirements on the range resolution, the maximum detectable range and the allowable integration time.

Thomson, J. A. L.↗
NASA NTRS1976

Secondary cosmic-ray electrons and positrons from 1 to 100 GeV in the upper atmosphere and interstellar space, and interpretation of a recent positron flux measurement

Secondary electron and positron fluxes generated in interstellar space and in the atmosphere from the decays of pions and kaons in inelastic nuclear interactions are calculated by Monte Carlo techniques for lepton energies in the range from 1 to 100 GeV and an assumed thickness of 10 g/sq cm or less for the interstellar or atmospheric material. A simple and accurate analytical model which summarizes the Monte Carlo results and identifies the essential parameters involved is developed and used to interpret a previous positron measurement. It is found that the thickness of interstellar and source material is about 4.3 g/sq cm for cosmic-ray positrons with energies exceeding 4 GeV, a result that is difficult to reconcile with recently proposed two-containment-volume propagation models which predict a thickness of 1.8 g/sq cm for the same energies on the basis of the energy dependence of the measured (Li+Be+B)/(C+O) ratio. It is shown that single-containment-volume (galactic) models invoking an energy-dependent leakage lifetime are compatible with the positron data, but lack a mechanism to explain the energy dependence.

Orth, C. D.↗
NASA NTRS1976

Nitric oxide formation by meteoroids in the upper atmosphere

The process of nitric oxide formation during atmospheric entry of meteoroids is analyzed theoretically. An ablating meteoroid is assumed to be a point source in a uniform flow with a continuum regime evolving in its wake. The amount of nitric oxide produced by high-temperature reactions of air in the continuum regime is calculated by numerical integration of chemical-rate equations. The results, when summed over the observed mass, velocity, and entry-angle distributions of meteoroids, provide annual global production rates of nitric oxide as a function of altitude. The peak production of nitric oxide is found to occur at altitudes between 90 and 100 km, the total annual rate being about 40 million kg. The present results suggest that the large concentration of nitric oxide observed below 95 km could be attributed to meteoroids instead of photodissociation of nitrogen.

Menees, G. P.↗
NASA NTRS1976

Application of trajectory optimization techniques to upper atmosphere sampling flights using the F-15 Eagle aircraft

Atmospheric sampling has been carried out by flights using an available high-performance supersonic aircraft. Altitude potential of an off-the-shelf F-15 aircraft is examined. It is shown that the standard F-15 has a maximum altitude capability in excess of 100,000 feet for routine flight operation by NASA personnel. This altitude is well in excess of the minimum altitudes which must be achieved for monitoring the possible growth of suspected aerosol contaminants.

Hague, D. S.↗
NASA NTRS1977

Interhemispheric survey of minor upper atmospheric constituents during October - November 1976

The CV-990 aircraft coordinated several flights with a NASA U-2 aircraft, NOAA ground station measurements in Alaska, Hawaii, and American Samoa, and with Australian and New Zealand ground stations, aircraft, and a balloon experiment in the Southern hemisphere. Data were obtained for species including ozone, total ozone, the oxides of nitrogen, the chlorofluoromethanes, water vapor, nitric acid, carbon monoxide, carbon dioxide, hydrogen chloride, Aitken nuclei, ammonia, aerosols, temperatures, and winds. Individual experiment results and selected analyses are presented. The experimental data include total column densities, latitude variations, interhemisphere differences, and vertical profiles.

Gauntner, D. J.↗
NASA NTRS1977

Pulsating aurora induced by upper atmospheric barium releases

The paper reports the apparent generation of pulsating aurora by explosive releases of barium vapor near 250 km altitude. This effect occurred only when the explosions were in the path of precipitating electrons associated with the visible aurora. Each explosive charge was a standard 1.5 kg thermite mixture of Ba and CuO with an excess of Ba metal which was vaporized and dispersed by the thermite explosion. Traces of Sr, Na, and Li were added to some of the charges, and monitoring was achieved by ground-based spectrophotometric observations. On March 28, 1976, an increase in emission at 5577 A and at 4278 A was observed in association with the first two bursts, these emissions pulsating with roughly a 10 sec period for approximately 60 to 100 sec after the burst.

Deehr, C.↗
NASA NTRS1977

Space-borne power conversion into a microwave beam and its impact on the environment of the upper atmosphere

The possible effect of microwave beams transmitted from Solar Power Satellites on the ionosphere has been studied theoretically. Particular attention is given to microwave-beam-heating of the F and D layers and theoretical predictions of such ionospheric modifications are used to determine resulting effects on the transmission efficiency of communication and navigation systems. It is recommended that a three-pronged technology and demonstration program be established to study microwave effects. The program would include theoretical studies, ground-based heating experiments, and an orbital experimental program for phase control of the microwave power transmission system.

Maynard, O. E.↗
NASA NTRS1977

Occultation of Epsilon Geminorum by Mars. II - The structure and extinction of the Martian upper atmosphere

The occultation of Epsilon Geminorum by Mars on April 8, 1976, was observed at three wavelengths and 4-ms time resolution with the 91-cm telescope aboard NASA's G. P. Kuiper Airborne Observatory. Temperature, pressure, and number-density profiles of the Martian atmosphere were obtained for both the immersion and emersion events. Within the altitude range 50-80 km above the mean surface, the mean temperature is about 145 K, and the profiles exhibit wavelike structures with a peak-to-peak amplitude of 35 K and a vertical scale of about 20 km. The ratio of the refractivity of the atmosphere at 4500 A and 7500 A is consistent with the atmospheric composition measured by Viking 1. From the 'central flash' - a bright feature in the light curve midway between immersion and emersion - an optical depth at 4500 A of 3.3 + or - 1.7 per km atm (about 0.23 per equivalent Martian air mass) is found for the atmosphere about 25 km above the mean surface near the south polar region. This large value and its weak wavelength dependence rule out Rayleigh scattering as the principal cause of the observed extinction.

Elliot, J. L.↗
NASA NTRS1977

Coherent wave induced particle precipitation into the upper atmosphere

A description is presented of the results of a computer simulation involving a study of the particle precipitation induced by coherent VLF waves in the magnetosphere. The results of a computation for a 10 picoweber/sq m wave amplitude are shown in a graph. The precipitated flux for three different energies is given in a table. For 1.5 keV the energy deposition rate is about 0.8 erg/sq cm-sec, almost as intense as a moderate aurora. It is concluded that significant energy is deposited by a wave of 10 picoweber/sq m intensity. Such a wave amplitude is representative of highly coherent VLF wave types that are found in the magnetosphere. On the basis of the considered results it appears that controlled VLF wave injection in the magnetosphere could be an important and useful tool to study the coupling processes between the atmosphere and magnetosphere.

Inan, U. S.↗
NASA NTRS1978

Photoelectrons in the upper atmosphere - A formulation incorporating effects of transport

A technique for solving the problem of photoelectron spatial transport and spectral degradation is presented. The developed model, which allows for a relatively complete description of the relevant transport and collisional physics, can be applied to study processes at either low or high altitude, and may be used to investigate interhemispheric transport. The technique involves dividing the spatial dimension into a set of discrete ordinates and calculating the photoelectron intensity for a specific energy at each point in space and at a set of angle points. The selected range of the energy spectrum was covered completely by a set of energy bins, and the photoelectron intensity in the highest energy bin was calculated first by assuming that the only source term was derived from photoionization. The method is similar to a method used in radiative transfer theory. Spatial and angular redistribution of electrons play a dominant role at heights above 400 km.

Prather, M. J.↗
NASA NTRS1978

Use of the Jacchia /1977/ empirical model in a dynamical model of upper-atmospheric helium

This brief report describes an investigation of the effects of using the Jacchia (1977) model in place of the Jacchia (1971) model for specifying the background gas pressure in the theoretical model of thermospheric helium described by Straus, et al. (1977). Changes in the global transport of helium caused by a small increase in the latitudes at which the background gas pressure extrema occur lead to much better agreement of the model predictions with data taken by the mass spectrometers on board the Esro 4 and OGO 6 satellites.

Straus, J. M.↗
NASA NTRS1978

Density models for the upper atmosphere

Consideration is given to three contemporary atmospheric density models which have been selected as the best candidates to meet the requirements of satellite missions. The models considered are the Analytic Jacchia-Roberts Model, the Modified Harris-Priester Model, and the U.S.S.R. Cosmos Satellite Derived Density Model. Each of the models and their respective variations is discussed separately, and a comparison of the computational characteristics of the models is presented. Finally, recommended modifications for improving both the computation speed and accuracy are presented.

Dowd, D. L.↗
NASA NTRS1978

Comment on ion and electron temperatures in the Martian upper atmosphere

Ion temperature profiles measured by the retarding potential analyzers on Viking I and II are examined. It is found that the thermal conduction must be modified by other transport processes or by the presence of magnetic fields to account for the observed profiles. Such processes also effect the electron temperature profile, which, however, was not measured. Estimates of the magnetic field parameters are obtained assuming the magnetic field is the dominant effect.

Johnson, R. E.↗
NASA NTRS1979

A parachute system for upper atmospheric studies

The Goddard Space Flight Center's Sounding Rocket Division successfully flight tested a high altitude, low velocity, 63.5 foot cross parachute system. The system was developed to provide a platform for atmospheric studies at altitudes higher than those attainable with balloons. This paper represents the approach taken to determine the necessary conditions for a successful apogee deployment of the parachute. The test flight deployed the parachute system at an apogee altitude of 61 kilometers. Post-flight results of rocket and parachute performance are compared to the preflight analyses.

Maksimovic, V. M.↗
NASA NTRS1979

Venus upper atmosphere neutral gas composition - First observations of the diurnal variations

Measurements of the composition, temperature, and diurnal variations of the major neutral constituents in the thermosphere of Venus are being made with a quadrupole mass spectrometer on the Pioneer Venus Orbiter. Concentrations of carbon dioxide, carbon monoxide, molecular nitrogen, atomic oxygen, and helium are presented, in addition to an empirical model of the data. The concentrations of the heavy gases, carbon dioxide, carbon monoxide, and molecular nitrogen, rapidly decrease from the evening terminator toward the nightside; the concentration of atomic oxygen remains nearly constant and the helium concentration increases, an indication of a nightside bulge. The kinetic temperature inferred from scale heights drops rapidly from 230 K at the terminator to 130 K at a solar zenith angle of 120 deg, and to 112 K at the antisolar point.

Niemann, H. B.↗