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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 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Stratospheric constituent distributions from balloon-based limb thermal emission measurements

This research task deals with an analysis of infrared thermal emission observations of the Earth's atmosphere for determination of trace constituent distributions. Infrared limb thermal emission spectra in the 700-2000 cm(exp -1) region were obtained with a liquid nitrogen cooled Michelson interferometer-spectrometer (SIRIS) on a balloon flight launched from Palestine, Texas, at nighttime on September 15-16, 1986. An important objective of this work is to obtain simultaneously measured vertical mixing ratio profiles of O3, H2O, N2O, NO2, N2O5, HNO3 and ClONO2 and compare with measurements made with a variety of techniques by other groups as well as with photochemical model calculations. A portion of the observed spectra obtained by SIRIS from the balloon flight on September 15-16, 1986, has been analyzed with a focus on calculation of the total nighttime odd nitrogen budget from the simultaneously measured profiles of important members of the NO(sub x) family. The measurements permit first direct determination of the nighttime total odd nitrogen concentrations NO(sub y) and the partitioning of the important elements of the NO(sub x) family.

Abbas, Mian M.↗
NASA NTRS1991

XES studies of density of states of high temperature superconductors

X-ray emission spectroscopic studies concerning the superconducting crystals, thin films, and ceramics of the Y-Ba-Cu-O, Tm-Ba-Cu-O, Bi-Sr-Ca-Cu-O, Bi-Pb-Sr-Ca-Cu-O, and Tl-Ba-Ca-Cu-O types are presented. The contributions of the 13d(9)L, 13d(10)L, 13d(10)LL, and 13d(10)L(2) configurations, where L denotes a ligand hole at the oxygen orbitals in the spectroscopic pattern of these superconductors are discussed. An attempt to connect the x-ray 'as registered' Cu L(alpha) emission spectra with the density of states close to the Fermi level, considering an influence of the CuL3 absorption edge, is presented. The corrected intensity distributions below the Fermi level are found to correspond to the theoretical density of states. Furthermore, an approach to the average valence of copper basing on the account of the self-absorption and fluorescence effects and on the configurations listed above is shown. The average valence of copper in the materials investigated is estimated to lie in the range of +2.10 to 2.32 when the formal trivalent copper is considered as that characterized by the 13d(9)L configuration. The density of states at the Fermi level was estimated to be 2.4 states/eV-cell for a Bi-Sr-Ca-Cu-O crystal and 3.6 states/eV-cell for a Tl-Ba-Ca-CU-O ceramic.

Jasiolek, Gabriel↗
NASA NTRS1992

Flouorescence measurements of the thermal control coatings on LDEF experiments S0069 and A0114

Strong fluorescence emissions were observed, during post flight ultraviolet light inspection of experiments S0069 and A0114, from some of the surfaces exposed to the space environment. Subsequent wavelength measurements of the fluorescence emission characteristics, indicated large changes occurred between controls and exposed materials. Black urethane based coatings, especially ones having a silicone atomic oxygen protective overcoat, appear bright yellow under ultraviolet exposure. Measurements showed that the urethane based coatings had their emission spectra shifted into the visible wavelength range. In contrast, zinc oxide pigment type coatings showed a different effect, which was a quenching or reduction of their fluorescence versus exposure time. Silver Teflon bonded to aluminum with acrylic adhesive also showed a slight measurable fluorescence, which was found to originate in the acrylic adhesive.

Zwiener, James M.↗
NASA NTRS1992

The thermal structure, dust loading, and meridional transport in the Martian atmosphere during late southern summer

We have derived a comprehensive picture of the thermal structure and dust loading of the Martian atmosphere in a relatively clear period during late southern summer. Using a new technique for the simultaneous retrieval of atmospheric temperatures and airborne dust abundances, we examined a subset of the Mariner 9 infrared interferometer spectrometer (IRIS) thermal emission spectra spanning L sub s = 343 degrees to 348 degrees. Global maps of temperature and dust optical depth as functions of latitude (plus or minus 90 degrees), altitude (approx. 0-60 km), and Mars local time of day were constructed from the profiles from individual spectra. One of the principal conclusions from this work is that both dayside and nightside atmospheric temperatures at altitudes above about 40 km are warmer over the winter (north) polar regions than over the equator or the summer (south) polar regions. These anomalous temperatures are consistent with ground-based observations of polar warming at higher altitudes (50-85 km), and they indicate that the atmosphere is not in radiative equilibrium. Zonal-mean zonal winds are derived from the observed meridional gradients of the zonally averaged temperatures assuming geostrophy and zero surface zonal wind. The intense eastward jets (with velocities exceeding 120 m/s) correspond to regions of strong horizontal temperature gradients. Similar calculations have been reported previously, but they were not global in coverage. Both the zonal-mean meridional circulation and large-scale waves contribute to the north-south atmospheric transport.

Santee, M.↗
NASA NTRS1992

Atmospheric and surface temperatures and airborne dust amounts during late southern summer from Mariner 9 IRIS data

The temperature structure and dust loading of the Martian atmosphere are investigated using thermal emission spectra recorded in 1972 by the Mariner 9 infrared interferometer spectrometer (IRIS). The analysis focuses on a subset of data consisting of approximately 2400 spectra obtained near the end of the southern summer season (L(sub s) equal to 343 deg to 348 deg), after the global dust storm had largely abated and airborne dust amounts were subsiding to background values. Simultaneous retrieval of the vertical distribution of both atmospheric temperature and dust optical depth is accomplished through an iterative procedure which is performed on each individual spectrum. The atmospheric transmittances are calculated using a Voigt quasi-random band model, which includes absorption by CO2 and dust, but neglects the effects of multiple scattering. Vertical profiles of temperature and dust optical depth are obtained using modified algorithms. These profiles are used to construct global maps of temperature and dust optical depth as functions of latitude (+/- 90 deg), altitude (approximately 0-50 km), and local time of day.

Santee, M.↗
NASA NTRS1991

Spectroscopic measurement of HO2, H2O2, and OH in the stratosphere

Stratospheric concentrations of HO2, H2O2, and OH have been retrieved simultaneously from the far-infrared emission spectra obtained with a balloon-borne Fourier transform spectrometer in June 1983 at 32 deg N latitude. Retrieved concentrations of HO2 and H2O2 are reported, along with vertical distributions of OH which were reported in an earlier paper for the afternoon, sunset, and nighttime periods for altitudes from 26 to 38 km. HO2 distributions are obtained with uncertainties that are about the same as OH for the same vertical range and for the afternoon and sunset periods. H2O2 concentration is obtained at an altitude of 30 km for the period that covers afternoon and sunset hours. The retrieved concentrations of these HO(x) species agree well with other individually measured results and the steady state photochemical predictions. The ratio HO2/OH at around 32 km seems to increase from the afternoon period to the sunset period.

Park, J. H.↗
NASA NTRS1990

Mechanical testing of large cryogenic structures

The mechanical testing performed on the Cryogenic Limb Array Etalon Spectrometer (CLAES) instrument installed on the Upper Atmosphere Research Satellite is discussed. The CLAES determines temperatures and concentrations of stratospheric minor species as a function of altitude by measuring the atmospheric infrared emission spectra. CLAES is based on a telescope optical system and infrared spectrometer which are cooled with cryogens.

Newkirk, Roger↗
NASA NTRS1992

Observations of VHF emissions from 50-mA electron beam injections in the ionosphere that are associated with beam-induced discharges

Results are presented of observations of strong VHF plasma waves with amplitudes in excess of 0.1 mV/m (Hz)1/2 associated with 50 mA electron beam injections in the ionosphere. Data from three swept-frequency receivers carried on two daughter payloads are analyzed to determine the emission spectra of the electron beam for various energies and currents. These results were obtained from the rocket-borne experiment SCEX 3, NASA flight 39.002 UE, launched February 1, 1990. The accelerator payload also carried photometers, which measured luminosity at wavelengths of 391.4 and 380.5 nm. Several times during electron gun activity the measured luminosity increased much faster than proportional to the beam current. This nonlinear increase is evidence that a discharge is occurring in the vicinity of the accelerator payload. It is inferred from the uniform distribution of the luminosity around the accelerator payload that the observed discharge extends significantly outside the beam cylinder.

Goerke, R. T.↗
NASA NTRS1990

Laser-induced fluorescence of phosphors for remote cryogenic thermometry

Remote cryogenic temperature measurements can be made by inducing fluorescence in phosphors with temperature-dependent emissions and measuring the emission lifetimes. The thermographic phosphor technique can be used for making precision, noncontact, cryogenic-temperature measurements in electrically hostile environments, such as high dc electric or magnetic fields. The National Aeronautics and Space Administration is interested in using these thermographic phosphors for mapping hot spots on cryogenic tank walls. Europium-doped lanthanum oxysulfide (La2O2S:Eu) and magnesium fluorogermanate doped with manganese (Mg4FGeO6:Mn) are suitable for low-temperature surface thermometry. Several emission lines, excited by a 337-nm ultraviolet laser, provide fluorescence lifetimes having logarithmic dependence with temperature from 4 to above 125 K. A calibration curve for both La2O2S:Eu and Mg4FGeO6:Mn is presented, as well as emission spectra taken at room temperature and 11 K.

Beshears, D. L.↗
NASA NTRS1992

The low-energy, charge-transfer excited states of 4-amino-4-prime-nitrodiphenyl sulfide

Absorption and emission spectra of 4-amino-4-prime-nitrodiphenyl sulfide in polar and nonpolar solvents were used to characterize and assign the low-energy excited states of the molecule. Fluorescence-excitation anisotropy spectra and fluorescence quantum yields were also used to characterize the photophysics of these states. The lowest-energy fluorescent singlet state was determined to be an intramolecular charge transfer (ICT) state involving transfer of a full electron charge from the amino to the nitro group yielding a dipole moment of about 50 D. A low-energy, intense absorption band is assigned as a transition to a different ICT state involving a partial electron charge transfer from sulfur to the nitro group.

O'Connor, Donald B.↗
NASA NTRS1992

Fluorescence of thermal control coatings on S0069 and A0114

Many of the thermal control surfaces exposed to the space environment during the 5.8 year LDEF mission experienced changes in fluorescence. All of the thermal control coatings flown on LDEF experiments S0069 and A0114 were characterized for fluorescence under ambient conditions. Some of the black coatings, having protective overcoats, appear bright yellow under ultraviolet exposure. Urethane based coatings exhibited emission spectra shifts toward longer wavelengths in the visible range. Zinc oxide pigment based coatings experienced a quenching of fluorescence, while zinc orthotitanate pigment based and other ceramic type coatings had no measurable fluorescence.

Zwiener, James M.↗
NASA NTRS1992

Asteroids, Comets, Meteors 1991

Papers from the conference are presented and cover the following topics with respect to asteroids, comets, and/or meteors: interplanetary dust, cometary atmospheres, atmospheric composition, comet tails, astronomical photometry, chemical composition, meteoroid showers, cometary nuclei, orbital resonance, orbital mechanics, emission spectra, radio astronomy, astronomical spectroscopy, photodissociation, micrometeoroids, cosmochemistry, and interstellar chemistry.

Harris, Alan W.↗
NASA NTRS1992

Stratospheric ethane on Neptune - Comparison of groundbased and Voyager IRIS retrievals

Near-simultaneous ground and spacecraft measurements of 12-micron ethane emission spectra during the Voyager encounter with Neptune have furnished bases for the determination of stratospheric ethane abundance and the testing and constraining of Neptune methane-photochemistry models. The ethane retrievals were sensitive to the thermal profile used. Contribution functions for warm thermal profiles peaked at higher altitudes, as expected, with the heterodyne functions covering lower-pressure regions. Both constant- and nonconstant-with-height profiles remain candidate distributions for Neptune's stratospheric ethane.

Kostiuk, Theodor↗
NASA NTRS1993

Thermal structure and dust loading of the Martian atmosphere during late southern summer - Mariner 9 revisited

Thermal emission spectra recorded by the Mariner 9 IR interferometer spectrometer (IRIS) are used to investigate the temperature structure and dust loading of the Martian atmosphere. The analysis is restricted to a subset of the IRIS data consisting of approximately 2400 spectra in a 12-day period extending from LS of 343 to 348 deg, corresponding to late southern summer on Mars. The largest column-integrated 9-micron dust optical depths (about 0.4) occur over the equatorial regions. The highest atmospheric temperatures (greater than 260 K) are found at low altitudes near the subsolar latitude (about 6 deg S), while the coldest temperatures (less than 150 K) are found at levels near 1.0 mbar over the winter pole. The existence of a net zonally averaged meridional circulation with rising motion at low latitudes, poleward flow at altitudes above 40 km, and subsidence over the poles is suggested.

Santee, Michelle↗
NASA NTRS1992

Vibrational and rotational temperature measurements in a shock tube

Vibrational and rotational temperatures in nitrogen test gas relaxing behind a normal shock are measured using the emission spectra of N2(+)(1-) and N2(2+) band systems in an electric-arc driven shock tube, at a shock velocity of 6.2 km/sec. The results are compared with similar data obtained by AVCO-Everett Research Laboratory during the 1960s. The vibrational and rotational temperatures in the equilibrium region obtained in the present experiment agreed with those of AVCO, but those in the nonequilibrium region are greatly different from the AVCO results. The measured rotational temperature seems to be in nonequilibrium with the translational temperature, contradicting the two-temperature model widely used in CFD. Also, the relaxation rates for both N2(+) and N2 molecules seem to be of the same order.

Sharma, S. P.↗
NASA NTRS1993

Balloon-borne submillimeterwave stratospheric measurements

A new remote sensing instrument, the Submillimeterwave Limb Sounder, has been developed to simultaneously measure ClO, HCl, O3 and HO2 from high altitude balloon and aircraft platforms. The instrument is a double sideband heterodyne radiometer measuring atmospheric thermal emission spectra near 640 GHz from the Earth's limb. The instrument was flown in April and October, 1991 and in February, 1992 on high altitude balloon platforms over the southwestern United States.

Stachnik, R. A.↗
NASA NTRS1993

Remote sensing x ray fluorescence spectrometry for future lunar exploration missions

Measurement of discrete line X-ray emission from space can be used to obtain both qualitative and quantitative elemental surface composition information. Remote orbital X-ray elemental analysis is the measurement of characteristic X-rays following the interaction of solar X-rays with the surface of a given solid body. Thus, X-ray emission from a surface is strongly dependent on the incident solar spectrum as well as on the chemical composition of the surface. In this paper, the relationship between the solar flux and the major lunar element fluorescence and scattered X-ray flux is characterized. A model was developed to calculate lunar surface X-ray fluorescence emission spectra under a variety of solar conditions and, in particular, conditions that might be expected for a Lunar Scout mission proposed for 1995 or 1996. This time period should be during solar minimum.

Clark, Pamela E.↗