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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Use of LEED, Auger emission spectroscopy and field ion microscopy in microstructural studies.

The studies reported were conducted to gain a fundamental understanding of adhesion and dynamic friction on an atomic or microscopic level. Fundamental aspects of low energy electron diffraction (LEED), Auger emission spectroscopy (AES), and field ion microscopy (FIM) are discussed. Typical results of studies conducted are considered, giving attention to LEED-AES experiments, pin and disk experiments, and field ion microscope investigations.

Ferrante, J.↗
NASA NTRS1972

K-Ar dating of lunar fines - Apollo 12, Apollo 14, and Luna 16.

K-Ar ages were determined on a 6-in. double-focus mass spectrometer in fines of less than 1 mm from Apollo 14 and 16, and Luna 16 lunar soil samples. Age estimates of about 2.8 AE and about 4.0 AE are suggested for the two low-K components whose presence in the samples must be assumed to accommodate the age data. An average value of 0.1849 plus or minus 0.0008 was obtained for the Ar-18/Ar-36 ratio in the solar wind from ordinate intercept correlations for the Apollo 14 and Luna 16 samples. Cosmic ray exposure ages were close to 440 m.y. for both Apollo 14 samples and close to 840 m.y. for both Luna 16 samples.

Pepin, R. O.↗
NASA NTRS1973

The Atmosphere Explorer mission.

Summary of the general scientific objectives of the Atmosphere Explorer (AE) mission. The overall purpose of the AE mission is shown to be the performance of simultaneous measurements needed for cause and effect studies that are to provide a detailed understanding of the physical processes governing the lower thermosphere and ionosphere.

Dalgarno, A.↗
NASA NTRS1973

The Atmosphere Explorer spacecraft system.

Brief description of the design goals, spacecraft, data system, and data analysis concept for the Atmosphere Explorer (AE) mission. The AE mission is shown to have been conceived and to be implemented for making possible a variety of studies of the lower thermosphere. The spacecraft support system, including an onboard propulsion system, will enable investigations to be carried out deep in the thermosphere and at all points of aeronomic significance about the earth.

Spencer, N. W.↗
NASA NTRS1973

The Bennett ion-mass spectrometer on Atmosphere Explorer-C and -E.

The Bennett spectrometer to be flown on Atmosphere Explorer-C and -E (AE-C and AE-E) is designed to measure, throughout the 120 to 4000-km orbit, the concentrations of all thermal positive ions in the mass range 1 to 72 amu and number density range 5 to 5,000,000 ions per cu cm. To reduce the buildup of ram pressure and facilitate measurements at low altitude, the analyzer is vented, and a multigrid ion-current collector is employed. An extensive command capability permits optimization of instrument parameters for particular measurement objectives; commandable functions include mass-scan range and period, the sensitivity-resolution characteristic of the analyzer, orifice potential, and in-flight calibration.

Brinton, H. C.↗
NASA NTRS1973

The EUV spectrophotometer on Atmosphere Explorer.

An extreme ultraviolet (EUV) spectrophotometer for measurements of solar radiation at wavelengths ranging from 140 to 1850 A will be included in the payload of each of the three Atmosphere-Explorer (AE) missions, AE-C, -D, and -E. The instrument consists of 24 grating monochromators, 12 of which can be telecommanded either to execute 128-step scans each covering a relatively small section of the total spectrophotometer wavelength range or to maintain fixed (command-selected) wavelength positions. The remaining 12 nonscan monochromators operate at permanently fixed wavelengths and view only a small fraction of the solar disk except for one viewing the whole sun in H Lyman alpha. Ten of the 12 scan-capable monochromators also view the entire solar disk since their primary function is to measure the total fluxes independent of the distribution of sources across the solar disk.

Hinteregger, H. E.↗
NASA NTRS1973

The photoelectron-spectrometer experiment on Atmosphere Explorer.

The Atmosphere Explorer (AE) photoelectron spectrometer experiment consists of electrostatic deflection-type electron spectrometers designed to measure the low-energy electron flux expected to be encountered along the AE orbit. The system has been designed to provide general information on the intensity, angular distribution, energy spectrum, and net flows along field lines as well as sufficient energy resolution to allow the fine details of the electron-energy spectrum to be studied. The instrumentation consists of two separate electron-spectrometer detector heads connected to a common electronics system for data processing and telemetry interfacing. The experiment will measure the electron-energy spectrum from 2 to 500 eV (and possibly to less than 0.1 eV).

Doering, J. P.↗
NASA NTRS1974

Auger electron spectroscopy and depth profile study of oxidation of modified 440C steel

Auger electron spectroscopy (AES) and sputtering were used to study selective oxidation of modified 440C steel. The sample was polycrystalline. Oxidation was performed on initially clean surfaces for pressures ranging from 1 x 10 to the minus 7th power to 1 x 10 to the minus 5th power torr and temperatures ranging from room temperature to 800 C. AES traces were taken during oxidation. In situ sputtering depth profiles are also obtained. A transition temperature is observed in the range 600 to 700 C for which the composition of the outer surface oxide changed from iron oxide to chromium oxide. Heating in vacuum about 5 x 10 to the minus 10 power torr to 700 C causes conversion of the iron oxide surface to chromium oxide.

Ferrante, J.↗
NASA NTRS1974

Auger analysis of films formed on metals in sliding contact with halogenated polymers

The use of Auger electron spectroscopy (AES) to search for transferred polymer must contend with the fact that there has been no published work on Auger analysis of polymers. Since this is a new area for AES, the Auger spectra of polymers and of halogenated polymers in particular is discussed. It is shown that the Auger spectra of halogenated polymers have certain characteristics that permit an assessment of whether a polymeric transfer film has been established by sliding contact. The discussion is general and the concepts should be useful in considering the Auger analysis of any polymer. The polymers chosen for this study are the halogenated polymers polytetrafluoroethylene (PTFE), polyvinyl chloride (PVC), and polychlorotrifluorethylene (PCTFE).

Pepper, S. V.↗
NASA NTRS1974

Analysis of data from spacecraft relating to stratospheric warmings

A detailed study of six different stratospheric warmings is described which establishes that the magnetic indices AE, Ap, and Dst display a marked increase 1 to 3 days before warming phenomena and a marked decrease at 0 and -4 days. The definite correlation of the warming phenomena with the AE index indicates that the auroral electrojet joule heating near 100 km may be the original source of the heating that influences the atmosphere at 50 km and below. Whether this heating is the primary cause or trigger of stratospheric warmings remains to be determined.

Weiss, R.↗
NASA NTRS1976

A direct measurement of the winter helium bulge

In late December 1975, the orbital configuration of the Atmosphere Explorer-D satellite made possible the measurement of the winter helium bulge within a single perigee pass. Shortly after the winter solstice, the perigee of the polar-orbiting AE-D satellite crossed the equator, at which time descending and ascending portions of the orbit stretched symmetrically over the Southern and Northern Hemispheres. The open-source neutral mass spectrometer (OSS) on board AE-D measured helium densities between the perigee (about 150 km) and altitudes of 650 km. During the time the perigee was at the equator, altitudes above approximately 550 km were located north and south at latitudes greater than 50-deg. Helium showed, in the winter hemisphere, densities that were a factor of 20 higher than at corresponding altitudes and latitudes in the Southern (summer) Hemisphere. Absolute densities of helium agree well with previous measurements.

Mauersberger, K.↗
NASA NTRS1976

Determination of exospheric neutral gas temperatures

The Atmosphere Explorer satellites (AE-C, -D, and -E) were initially placed into highly elliptical orbits with perigees around 140 km and apogees of 4000 km. As a result of such an orbital geometry, measurements of neutral constituents at high altitudes represent mainly vertical changes in densities. The influence of horizontal density gradients on measurements above 400 km is small. Under geomagnetically quiet conditions, the density profiles can be used to derive scale-height temperatures of the exosphere. The open-source neutral mass spectrometer (OSS) flown on all three AE-satellites measured neutral constituents such as N2, O, and N well above 400 km. The temperatures derived from scale heights show a good agreement among the constituents and the expected close correlation with the F10.7-cm solar flux. Satellites with highly elliptical orbits provide the opportunity to measure simultaneously both densities and temperatures.

Mauersberger, K.↗
NASA NTRS1976

Terrestrial kilometric radiation: 3-average spectral properties

A study is presented of the average spectral properties of terrestrial kilometric radiation (TKR) derived from observations made by radio astronomy experiments onboard the IMP-6 and RAE-2 spacecraft. As viewed from near the equatorial plane, TKR is most intense and most often observed in the 21-24 hr local time zone and is rarely seen in the 09-12 hr zone. The peak flux density usually occurs near 240 kHz, but there is evidence that the peak occurs at a somewhat lower frequency on the dayside. The frequency of the peak in the average flux spectrum varies inversely with increasing substorm activity as inferred from the auroral electrojet index (AE) from a maximum near 300 kHz during very quiet times to a minimum below 200 kHz during very disturbed times. The absolute flux levels in the 100-600 kHz TKR band increase significantly with increasing AE. The average power associated with a particular source region seems to decrease rapidly with increasing source altitude.

Kaiser, M. L.↗
NASA NTRS1977

Carbon distribution profiles in lunar fines

Radial distribution profiles of elemental carbon in lunar soils consisting of particles in the size range of 50 to 150 microns were investigated. Initial experiments on specimen preparation and the analysis of prepared specimens by Auger electron spectrometry (AES) and scanning electron microscopy (SEM) are described. Results from splits of samples 61501,84 and 64421,11, which were mounted various ways in several specimen holders, are presented. A low carbon content was observed in AES spectra from soil particles that were subjected to sputter-ion cleaning with 960eV argon ions for periods of time up to a total exposure for one hour. This ion charge was sufficient to remove approximately 70 nm of material from the surface. All of the physically adsorbed carbon (as well as water vapor, etc.) would normally be removed in the first few minutes, leaving only carbon in the specimen, and metal support structure, to be detected thereafter.

Hart, R. K.↗
NASA NTRS1977

Relationship between auroral substorms and the occurrence of terrestrial kilometric radiation

The correlation between magnetospheric substorms as inferred from the AE(11) index and the occurrence of terrestrial kilometric radiation (TKR) is examined. It is found that AE and TKR are well correlated when observations are made from above the 15-03 hr local time zone and are rather poorly correlated over the 03-15 hr zone. High-resolution dynamic spectra obtained during periods of isolated substorms indicate that low-intensity, high-frequency TKR commences at about the same time as the substorm phase. The substorm expansion phase corresponds to a rapid intensification and bandwidth increase of TKR. When combined with previous results, these new observations imply that many TKR events begin at low altitudes and high frequencies (about 400-500 kHz) and spread to higher altitudes and lower frequencies as the substorm expands.

Kaiser, M. L.↗
NASA NTRS1976

Adsorption of oxygen on W/100/ - Adsorption kinetics and structure

The adsorption of oxygen on W(100) single-crystal surfaces is studied by Auger electron spectroscopy (AES), flash desorption, low-energy electron diffraction (LEED), and retarding-field work-function measurements. The AES results reveal stepwise changes in the sticking coefficients in the coverage range 0 to 1 and activated adsorption at higher coverages. Upon room-temperature adsorption, a series of complex LEED patterns is observed. In layers adsorbed at 1050 K and cooled to room temperature, the p(2 x 1) structure is the first ordered structure observed. This structure shows a reversible order-disorder transition between 700 and 1000 K and is characterized by a work function which is lower than that of the clean surface. Heating room-temperature adsorbates changes their structure irreversibly. At temperatures below 750 K, some new structures are observed.

Bauer, E.↗
NASA NTRS1977

Triggering of substorms by solar wind discontinuities

The probability of triggering of polar substorms by a large-scale magnetospheric compression associated with a discontinuity in the solar wind has been examined statistically using ground magnetogram data, AE index data and satellite geomagnetic data on 125 sudden storm commencements observed during 1967-1970. The triggering probability was found to depend on the amplitude of the sudden storm commencement and on the degree of preceding AE activity. In almost all cases the triggering occurred when the B-Z component of the interplanetary magnetic field was negative or decreasing during the 30 min before the passage of the discontinuity. Transient geomagnetic responses with a time scale of Alfven wave propagation in the polar cap also depend on interplanetary magnetic field conditions.

Kokubun, S.↗