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At least 577 records · Page 32
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Correlation interferometric measurement of trace species in the atmosphere.

Two correlation interferometers, a breadboard model and an engineering model, have been designed, constructed, and tested for the measurement of selected atmospheric trace species. Test results showed that errors of less than 10% are attainable for atmospheric amounts of carbon monoxide and methane measured at 2.3 microns. Based on these results a program has been undertaken to determine the feasibility of measuring other trace species by correlation interferometry. It shown that in addition to carbon monoxide and methane, carbon dioxide, water vapor, ammonia, nitric oxide, nitrous oxide, nitrogen dioxide, and sulfur dioxide can also be accurately measured with this instrument.

Goldstein, H. W.↗
NASA NTRS1977

Minor species and aerosols

A variety of species were measured to tie together the efforts of one dimensional and multidimensional models. The existence of critical species in the stratosphere was established. An attempt was made to establish some order to the measurements that were made and the type of problems that exist.

Source record↗
NASA NTRS1977

Does application of the Rosiwal Principle to lunar soils require that concentrations of solar-wind-implanted species be grain-size independent

A reconsideration of the application of the Rosiwal Principle to lunar soils indicates a flaw in arguments put forth previously by Criswell (1975). Specifically, by introducing a boundary condition which must exist at the lunar surface, it is shown that concentrations of solar-wind-implanted species showing a dependence on grain size may be able to develop in soils at concentration levels below those required for saturation of grain surfaces. As a result, observed grain-size-dependent concentrations of solar-wind species in lunar soils do not necessarily require the exposure time scales or solar-wind fluxes deduced from the arguments of Criswell.

Becker, R. H.↗
NASA NTRS1978

Simulated null-gravity environments as applied to electrophoretic separations of biological species

The scale-up of electrophoretic separations to provide preparative quantities of materials has been hampered by gravity induced convection and sedimentation. The separation of biologically important species may be significantly enhanced by electrophoretic space processing. Simple demonstrations on past space flights have proven some principles. Several techniques have been evolved to study electrophoretic separations where the effects of gravity have been nullified or significantly reduced. These techniques employ mechanical design, density gradients and computer modeling. Utilization of these techniques for ground based studies will yield clues as to which biological species can be considered prime candidates for electrophoretic processing in zero-G.

Giannovario, J. A.↗
NASA NTRS1978

Global sensing of gaseous and aerosol trace species using automated instrumentation on 747 airliners

The Global Atmospheric Sampling Program (GASP) is collecting and analyzing data on gaseous and aerosol trace contaminants in the upper troposphere and lower stratosphere. Measurements are obtained from automated systems installed on four 747 airliners flying global air routes. Improved instruments and analysis techniques are providing an expanding data base for trace species including ozone, carbon monoxide, water vapor, condensation nuclei, and mass concentration of sulfates and nitrates. Simultaneous measurements of several trace species obtained frequently can be used to identify the source of the air mass as being typically tropospheric or stratospheric.

Perkins, P. J.↗
NASA NTRS1978

CIMATS - A correlation interferometer for the measurement of atmospheric trace species

A multigas correlation interferometer, based on the previously developed and tested COPE instrument, has been designed and fabricated and is presently undergoing laboratory testing. The CIMATS instrument has the capability to remotely measure densities of selected gaseous atmospheric species in the spectral range 2 to 2.5 and 4 to 10 microns. The sensor has been designed for both nadir viewing and earth limb viewing. As presently configured the sensor is capable of measuring ammonia, nitrous oxide, and carbon monoxide in the nonthermal infrared spectral region and carbon monoxide and sulfur dioxide in the thermal infrared. Other gaseous species can be measured by inclusion of additional narrow band filters.

Goldstein, H. W.↗
NASA NTRS1980

A continuation of base-line studies for environmentally monitoring Space Transportation Systems (STS) at John F. Kennedy Space Center. Volume 4: Threatened and endangered species of the Kennedy Space Center. Part 2: Threatened and endangered birds and other threatened and endangered forms

Data are presented which were collected by ground and aerial surveillance of 37 species of birds observed within the environs of KSC which are on lists of rare and endangered biota in Florida. Additional information was obtained on other threatened species such as the West Indian manatee, the salt marsh snake, the Indigo snake, the Gopher tortoise, the American alligator, and the Florida mouse. Results of the literature search were used to obtain a historical perspective and aid in the analysis of the field data collected.

Ehrhart, L. M.↗
NASA NTRS1979

Temperature and species concentration measurements in a swirl-stabilized combustor

An experimental evaluation of a swirl-stabilized combustor is presented. The combustor is composed of two confined, concentric, swirling jets. The inner jet flow is lean premixed methane and air; the outer flow is air. Combustion is stabilized on a swirl-induced recirculation zone. Mean temperature and mean concentrations of major species are measured throughout the combustor, including the recirculation zone. Fine wire thermocouples are used to measure temperature. A gas chromatograph and a chemi-luminescence analyzer are employed to analyze samples extracted by a water-cooled gas-sampling probe. Results are presented in the form of isotherms and isopleths of species concentration in the combustor for two swirl conditions: co-swirl and counter-swirl. The effects of swirl on the combustion are discussed in light of flame quenching due to rapid dilution and cooling of the reacting inner jet flow by mixing with the outer flow. Evidence for probe induced perturbations of the combustion process is observed.

Oven, M. J.↗
NASA NTRS1981

Studies of the role of metastables and doubly ionized species in the chemical and thermal structure of the Venusian and Martian ionospheres

Models of the upper atmospheres of Mars and Venus were constructed using Viking and Pioneer Venus data. The neutral densities, with the exception of NO, N(4S), N(2D) and N(2P) were taken from the measured values, along with the neutral, ion, and electron temperatures. Using solar fluxes and relevant cross sections, the production rates of ions and neutral fragments by photo and electron impact processes were computed. These production rates were combined with chemical production rates and loss along with one dimensional transport eddy diffusion, molecular and ambi polar diffusion, and thermal diffusion, to determine the densities of ions and odd nitrogen species. Preliminary calculations show that the chemistry of metastables and doubly ionized species is important in the ionospheres of Mars and Venus. Production of N(+) in metastable reactions is particularly important, and it explains the discrepancy between the measurements of earlier models. Production of CO(+) is also affected. Reactions of O(++) and O(+)(2D) with N2 have important consequences for the escape rate of atomic nitrogen from the Martian atmosphere.

Fox, J. L.↗
NASA NTRS1981

Optical absorption of carbon and hydrocarbon species from shock heated acetylene and methane in the 135-220 nm wavelength range

Absorption spectroscopy of carbon and hydrocarbon species has been performed in a shock tube at an incident shock condition for a wavelength range of 135-220 nm, in order to obtain information needed for calculating radiation blockage ahead of a planetary probe. Instrumentation consisted of high frequency response pressure transducers, thin-film heat transfer gages, or photomultipliers coupled by light pipes. Two test-gas mixtures, one with acetylene and the other with methane, both diluted with argon, were used to provide a reliable variation of C3 and C2H concentration ratio. Comparison of tests results of the two mixtures, in the temperature range of 3750 + or - 100 K, showed the main absorbing species to be C3. The wavelength for maximum absorption agrees well with the theoretical values of 7.68 eV and 8.03 eV for the vertical excitation energy, and a value of 0.90 for the electronic oscillator strength, obtained from the measured absorption band, is also in good agreement with the predicted value of 0.92.

Shinn, J. L.↗
NASA NTRS1982

A comprehensive model to determine the effects of temperature and species fluctuations on reaction rates in turbulent reacting flows

A principal element to be derived from modeling turbulent reacting flows is an expression for the reaction rates of the various species involved in any particular combustion process under consideration. A temperature-derived most-likely probability density function (pdf) was used to describe the effects of temperature fluctuations on the Arrhenius reaction rate constant. A most-likely bivariate pdf described the effects of temperature and species concentrations fluctuations on the reaction rate. A criterion is developed for the use of an "appropriate" temperature pdf. The formulation of models to calculate the mean turbulent Arrhenius reaction rate constant and the mean turbulent reaction rate is considered and the results of calculations using these models are presented.

Foy, E.↗
NASA NTRS1982

Transient species on Mars and Venus

The similarities between the atmospheres of Earth, Venus, and Mars are discussed. The following species are highlighted: NOx, HOx, and COx. The concentrations of the species were examined for all three planets.

Yung, Y. L.↗
NASA NTRS1981

Ultraviolet absorption studies of H2O and other species in comet comae with satellite telescope-spectrometers

It is noted that ultraviolet absorption by H2O and other species in the comae of comets could be detected by studying, with satellite telescope-spectrometers, the occultation of hot stars by comets. Observations of this type could produce the first detection of H2O, the fundamental parent molecule in comet comae, and give measures of molecular level populations. The capabilities of the High Resolution Spectrograph on Space Telescope, the first instrument suitable for such observations, are discussed. A Haser model is used to estimate the molecular column densities and to predict equivalent widths for lines of H2O, OH, CO, C, and O as functions of time and angular distance from a comet with a high H2O production rate. The minimum detectable equivalent widths are determined, thereby giving the maximum angular separation from such a comet at which H2O, OH, and CO could be studied. Estimated equivalent widths for CO, OH, and the resonance lines of C and O suggest that these species may also be detected.

Smith, P. L.↗
NASA NTRS1981

An advective model for two-dimensional transport of stratospheric trace species

A parameterization of two-dimensional transport is applied to photochemical models of stratospheric trace species. It is shown that in a first approximation, tracer transport in the meridional plane may be treated as an advective rather than a diffusive process. The concept of residual mean meridional circulation (Andrews and McIntyre, 1976; Boyd, 1976) is used in the model and shown to be a modified Eulerian mean, a good approximation to the Lagrangian mean motion. A simple example in which the equilibrium distribution is computed for a tracer with a uniform tropospheric source and a stratospheric sink proportional to the local mixing ratio demonstrates the potential of the proposed parameterization. The resulting distribution is found to agree qualitatively with the observed stratospheric distribution of trace species whose sources are in the troposphere.

Holton, J. R.↗
NASA NTRS1981

The feasibility of using time-dependent photochemical calculations to infer radical species concentrations from solar occultation absorption measurements

In connection with fast chemical reactions, short-lived stratospheric species experience rapid concentration variations at sunset and sunrise. For solar occultation absorption measurements, these rapid concentration variations may introduce significant errors with respect to the inference of atmospheric abundances for some species due to asymmetrical concentration distributions. Most retrieval algorithms assume that concentration distributions are spherically symmetric. The effect of this assumption on the accuracy of inferred concentrations has been studied by Kerr et al. (1977). The present investigation considers the feasibility of using a time-dependent one-dimensional photochemical model to provide detailed information about the asymmetrical distribution for use in the retrieval procedure. As shown by Boughner et al. (1980), diurnal effects can be represented by an inhomogeneity factor. It is found that the NO retrieval improves considerably with the inclusion of a correction factor containing the asymmetrical variations.

Larsen, J. C.↗
NASA NTRS1982

Candidate Species Selection: Cultural and Photosynthetic Aspects

Cultural information is provided for a data base that will be used to select candidate crop species for a controlled ecological life support system (CELSS). Lists of food crops which will satisfy most nutritional requirements of humans and also fit within the scope of cultural restrictions that logically would apply to a closed, regenerating system were generated. Cultural and environmental conditions that will allow the most rapid production of edible biomass from candidate species in the shortest possible time are identified. Cultivars which are most productive in terms of edible biomass production by (CE) conditions, and which respond to the ever-closed approach to optimization realized by each shortened production cycle are selected. The experimental approach with lettuce was to grow the crop hydroponically in a growth chamber and to manipulate such variables as light level and duration, day/night temperature, and nutrient form and level in the solution culture.

Mitchell, C. A.↗
NASA NTRS1982

Discovery of highly ionized species in the ultraviolet spectrum of Feige 24

A high-resolution ultraviolet spectrum of the nearby (90 pc) white dwarf binary Feige 24 (DA + M1-2 V) obtained with the International Ultraviolet Explorer satellite (IUE) reveals two sets of absorption features in the species C IV, Si IV, and N V. The low-velocity component (V approximately 1 km/s) arises from the local interstellar gas apparently ionized by the white dwarf. The second component, at high velocities (V approximately +83 km/s), arises in the atmosphere of the white dwarf in the Feige 24 system. The presence of this large velocity shift supplies the first strong evidence for narrow absorption cores due to high-temperature species in a white dwarf atmosphere. Observations around the orbital period will provide a direct measurement of the gravitational redshift and the mass of the white dwarf. The inferred hydrogen density is 0.008 per cu cm toward this source.

Dupree, A. K.↗
NASA NTRS1983

Lidar system analysis for measurement of atmospheric species

Several important aspects of lidar are discussed, which pertain to a system analysis of the applicability of certain types of lidar to specific measurement objectives. The differential absorption lidar (DIAL) technique is emphasized. A brief treatment of the DIAL technique is followed by a discussion of the comparison of DIAL with other lidar measurement techniques. Sensitivity expressions are presented for DIAL with either direct or coherent (heterodyne) detection systems. A treatment of the fundamental similarities and differences in using the UV and IR spectral regions for species measurements, such as backscattering properties, spectral characteristics of the absorbing species, and factors relevant to the optimization of the DIAL measurement accuracy, is also included. Finally, results obtained from an existing ground-based DIAL system used to measure water vapor profiles are briefly discussed.

Menzies, R. T.↗