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At least 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

An analysis of the first two years of GASP data

Distributions of mean ozone levels from the first two years of data from the NASA Global Atmospheric Sampling Program (GASP) show spatial and temporal variations in agreement with previous measurements. The standard deviations of these distributions reflect the large natural variability of ozone levels in the altitude range of the GASP measurements. Monthly mean levels of ozone below the tropopause show an annual cycle with a spring maximum which is believed to result from transport from the stratosphere. Correlations of ozone with independent meteorological parameters, and meteorological parameters obtained by the GASP systems show that this transport occurs primarily through cyclogenesis at mid-latitudes.

Holdeman, J. D.↗
NASA NTRS1976

Atmospheric ozone measurements made from B-747 airliners - Spring 1975

Atmospheric ozone in the upper troposphere and lower stratosphere north of the equator has been registered aboard two commercial B-747 airliners during the Spring of 1975. This monitoring is part of a much broader and continuing project developed by NASA and known as the Global Atmospheric Sampling Program (GASP). Additional flight and meteorological conditions have also been automatically recorded on board concurrent with the ozone measurements. Independently-derived tropopause pressure information was available from NMC data archives and was used to identify stratospheric and tropospheric flight. The composite ozone, flight and meteorological data are reported for selected dates in March, April, and May. Attention is drawn particularly to the vertical profiles of atmospheric ozone mixing ratio as a function of both distance from the tropopause and curvature of the streamlines. The GASP observations suggest that ozone levels typical of the lower stratosphere are often embedded in the upper troposphere, principally during occasions when cyclonic wind curvature was noted.

Falconer, P. D.↗
NASA NTRS1978

Inversion of the resonance line of Sr/+/ produced by optically pumping Sr atoms

A description is presented of an experiment which demonstrates the selective production of excited-state ions by an optical absorption from neutrals. An inversion on the resonance line of Sr(+) was produced by laser excitation of a two-electron transition, followed by ionization of one of the excited electrons by the same laser. A pulsed, mode-locked laser operating at 2680 A was used to excite atoms from the Sr ground level. The same laser then ionized the excited atoms. The 2680-A pump beam was generated by frequency doubling the output of a synchronously pumped mode-locked dye laser in a KDP crystal. It is pointed out that the reported results are significant for the construction of vacuum-ultraviolet and X-ray lasers. Many of the proposed methods for making such lasers depend on the selective production of excited-state ions.

Green, W. R.↗
NASA NTRS1979

A summary of research on the NASA-Global Atmospheric Sampling Program performed by the Atmospheric Sciences Research Center

The annual variations of ozone near the tropopause are derived from aircraft exhibit year-to-year differences which are not explicitly accounted for by the simple, classical ozone transport theory. Phenomena such as tropopause lifting, interannual variations in the rates of stratospheric-tropospheric exchange and meridional mixing, contribute differently to the distribution of ozone in this altitude region. Ozone encounter climatologies have been represented by global maps which show the probabilities of exceeding ambient ozone levels of 200, 300, and 400 ppbV along flight routes during the year. Continuous ozone records obtained from the GASP system revealed the presence of gravity waves whose wavelength is of the order 20 km. The GASP data cannot, however, be utilized for the evaluation of horizontal fluxes of such quantities as ozone, sensible heat, and zonal momentum; the data are too sparsely and irregularly distributed for the computation of stable correlations. Multiple species data from the unique circumglobal flight of a Pan American airliner on 28-30 October 1977 are discussed with particular regard to the apparent interhemispheric differences in tropospheric species concentrations, variation between the Arctic and Antarctic stratospheres, to possible covariations between species, and to potential source regions for various constituents.

Falconer, P. D.↗
NASA NTRS1978

An analysis of the first two years of GASP data

Distributions of mean ozone levels from the first two years of data from the NASA Global Atmospheric Sampling Program (GASP) show spatial and temporal variations in agreement with previous measurements. The standard deviations of these distributions reflect the large natural variability of ozone levels in the altitude range of the GASP measurements. Monthly mean levels of ozone below the tropopause show an annual cycle with a spring maximum which is believed to result from transport from the stratosphere. Correlations of ozone with independent meteorological parameters, and meteorological parameters obtained by the GASP systems show that this transport occurs primarily through cyclogenesis at mid-latitudes. The GASP water vapor data, analyzed with respect to the location of the tropopause, correlates well with the simultaneously obtained ozone and cloud data.

Holdeman, J. D.↗
NASA NTRS1978

Global atmospheric sampling program - Prospects for establishing a tropospheric ozone budget from commercial aircraft data

A preliminary analysis of zonally averaged, ozone concentration data obtained from commercial (GASP) aircraft between the equator and 60 deg North indicates that ozone in the upper troposphere exhibits a primary maximum during the spring, and, in middle latitudes, a secondary maximum in the summer of both 1975 and 1976. A late-fall/early-winter minimum also appears and seems consistent with previous upper air measurements. The April ozone maximum has been well documented and appears at the time when the stratospheric ozone content is greatest and cyclogenetic activity is most vigorous. However, the secondary maximum in June has not been widely observed or quoted as a unique feature. It is hypothesized that the rapid ascent of the tropopause between midspring and summer could account for the incorporation of ozone-rich, stratospheric air into the upper troposphere with a subsequent dilution during the following months. This may explain certain aspects of the annual ozone cycle in the lower troposphere which occasionally exhibit a bimodal distribution during the warm season.

Falconer, P. D.↗
NASA NTRS1979

Circumpolar measurements of ozone, particles, and carbon monoxide from a commercial airliner

Trace constituent data are presented from the unique flight of an airliner around the world over both poles. Relatively high resolution and simultaneous measurements of ozone, carbon monoxide, light-scattering particles, condensation nuclei, and meteorological parameters were obtained. The mutual variations of the data in the polar stratospheres, and in the tropical upper troposphere, are discussed in their meteorological setting. The data from the Arctic lower stratosphere are consistent with a tropospheric source of condensation nuclei, but not of carbon monoxide. Carbon monoxide mixing ratios in the Antarctic stratosphere averaged 44 ppbv. In the tropical troposphere they averaged 66 ppbv over the Pacific versus 89 ppbv over Africa. A local area of higher concentration (115 ppbv) was encountered over tropical Africa; its possible relation to carbon monoxide production by vegetation and deep convection is discussed. Evidence was found in the tropical upper troposphere of distinct boundaries between air masses of different temperature, ozone content, and particle content.

Pratt, R.↗
NASA NTRS1983

Aircraft measurements of trace gases and particles near the tropopause

Research activities which were performed using atmospheric constituent data obtained by the NASA Global Atmospheric Sampling Program are described. The characteristics of the particle size spectrum in various meteorological settings from a special collection of GASP data are surveyed. The relationship between humidity and cloud particles is analyzed. Climatological and case studies of tropical ozone distributions measured on a large number of flights are reported. Particle counter calibrations are discussed as well as the comparison of GASP particle data in the upper troposphere with other measurements at lower altitudes over the Pacific Ocean.

Falconer, P.↗
NASA NTRS1983

A preliminary evaluation of LANDSAT-4 thematic mapper data for their geometric and radiometric accuracies

Some LANDSAT thematic mapper data collected over the eastern United States were analyzed for their whole scene geometric accuracy, band to band registration and radiometric accuracy. Band ratio images were created for a part of one scene in order to assess the capability of mapping geologic units with contrasting spectral properties. Systematic errors were found in the geometric accuracy of whole scenes, part of which were attributable to the film writing device used to record the images to film. Band to band registration showed that bands 1 through 4 were registered to within one pixel. Likewise, bands 5 and 7 also were registered to within one pixel. However, bands 5 and 7 were misregistered with bands 1 through 4 by 1 to 2 pixels. Band 6 was misregistered by 4 pixels to bands 1 through 4. Radiometric analysis indicated two kinds of banding, a modulo-16 stripping and an alternate light dark group of 16 scanlines. A color ratio composite image consisting of TM band ratios 3/4, 5/2, and 5/7 showed limonitic clay rich soils, limonitic clay poor soils, and nonlimonitic materials as distinctly different colors on the image.

Podwysocki, M. H.↗
NASA NTRS1981

Anti-Stokes scattering as an XUV radiation source

Harris (1977) has shown that laser induced scattering from atoms stored in a metastable level may be used to produce an XUV radiation source with several unique properties, including narrow linewidth, tunability, linear polarization, picosecond pulsewidth, and relatively high peak spectral brightness. The present investigation provides a summary concerning the progress made on the use of this radiation source as a unique instrument for XUV spectroscopy, and as a possible flashlamp for a 200 A laser. Zych et al. (1978) demonstrated that the maximum spectral brightness of the source is that of a blackbody with a temperature of the metastable storage level. The peak count rate and peak spectral brightness of the anti-Stokes emission at 569 A are 17 times and 139 times greater than those of the 584 A resonance line. The anti-Stokes process was employed as an external source of radiation for high resolution spectroscopy of the 3p6 shell of potassium. Attention is also given to emission spectroscopy of lithium, metastable levels which are appropriate for storage, and a hollow cathode discharge.

Harris, S. E.↗
NASA NTRS1982

Laser techniques for spectroscopy of core-excited atomic levels

We discuss three techniques which allow the use of tunable lasers for high resolution and picosecond time scale spectroscopy of core-excited atomic levels. These are: anti-Stokes absorption spectroscopy, laser induced emission from metastable levels, and laser designation of selected core-excited levels.

Harris, S. E.↗
NASA NTRS1985

A Preliminary Evaluation of LANDSAT-4 Thematic Mapper Data for Their Geometric and Radiometric Accuracies

Some LANDSAT thematic mapper data collected over the eastern United States were analyzed for their whole scene geometric accuracy, band to band registration and radiometric accuracy. Band ratio images were created for a part of one scene in order to assess the capability of mapping geologic units with contrasting spectral properties. Systematic errors were found in the geometric accuracy of whole scenes, part of which were attributable to the film writing device used to record the images of film. Band to band registration showed that bands 1 through 4 were registered to within one pixel. Likewise, bands 5 and 7 also were registered to within one pixel. However, bands 5 and 7 were misregistered with bands 1 through 4 by 1 to 2 pixels. Band 6 was misregistered by 4 pixels to bands 1 through 4. Radiometric analysis indicated two kinds of banding, a modulo-16 stripping and an alternate light dark group of 16 scanlines. A color ratio composite image consisting of TM band ratios 3/4, 5/2, and 5/7 showed limonitic clay rich soils, limonitic clay poor soils, and nonlimonitic materials as distinctly different colors on the image.

Podwysocki, M. H.↗
NASA NTRS1990

Laboratory Simulation of the Effect of Rocket Thrust on a Precessing Space Vehicle

Ground tests of solid propellant rocket motors have shown that metal-containing propellants produce various amounts of slag (primarily aluminum oxide) which is trapped in the motor case, causing a loss of specific impulse. Although not yet definitely established, the presence of a liquid pool of slag also may contribute to nutational instabilities that have been observed with certain spin-stabilized, upper-stage vehicles. Because of the rocket's axial acceleration, absent in the ground tests, estimates of in-flight slag mass have been very uncertain. Yet such estimates are needed to determine the magnitude of the control authority of the systems required for eliminating the instability. A test rig with an eccentrically mounted hemispherical bowl was designed and built which incorporates a follower force that properly aligns the thrust vector along the axis of spin. A program that computes the motion of a point mass in the spinning and precessing bowl was written. Using various RPMs, friction factors, and initial starting conditions, plots were generated showing the trace of the point mass around the inside of the fuel tank. The apparatus will incorporate future design features such as a variable nutation angle and a film height measuring instrument. Data obtained on the nutational instability characteristics will be used to determine order of magnitude estimates of control authority needed to minimize the sloshing effect.

Alvarez, Oscar↗
NASA NTRS1989

Selective simulation and selective sensor interpretation in monitoring

An approach to selective processing in monitoring is described. The approach is designed to provide informative feedback on whether a system is performing nominally in the current operating context without exceeding available resources for prediction and interpretation. At the center of the approach to selective sensor interpretation and simulation is a causal model of the system being monitored. The architecture of the monitoring system, called PREMON, is described as well as how causal models of physical systems are represented and simulated.

Doyle, Richard J.↗
NASA NTRS1989

The women in science and engineering scholars program

The Women in Science and Engineering Scholars Program provides scientifically talented women students, including those from groups underrepresented in the scientific and technical work force, with the opportunity to pursue undergraduate studies in science and engineering in the highly motivating and supportive environment of Spelman College. It also exposes students to research training at NASA Centers during the summer. The program provides an opportunity for students to increase their knowledge of career opportunities at NASA and to strengthen their motivation through exposure to NASA women scientists and engineers as role models. An extensive counseling and academic support component to maximize academic performance supplements the instructional and research components. The program is designed to increase the number of women scientists and engineers with graduate degrees, particularly those with an interest in a career with NASA.

Falconer, Etta Z.↗