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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 163 records · Page 9
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Orbit design for solar and dual satellite occultation measurements of atmospheric constituents

Two types of satellite-based occultation missions are considered for measuring atmospheric constituents. Nominal cases for each type are presented to demonstrate representative solutions to orbit design problems. For the solar occultation mode, large areas of the globe can be covered during a 1-year mission, but the measurements are limited to local dawn or dusk. For the dual satellite mode, with a laser aboard a second satellite to act as a source, diurnal coverage can be obtained at the expense of more complex systems and mission scenarios. In this mode, orbit pairs are selected which maintain their relative orbit plane geometry while their differing periods drive cyclic patterns of latitude coverage. A simulated 1-year solar occultation mission is used to illustrate one way of analyzing occultation data by averaging measurements within bands of constant latitude.

Brooks, D. R.↗
NASA NTRS1978

Upper limits to trace constituents in Jupiter's atmosphere from an analysis of its 5 micrometer spectrum

A high-resolution spectrum of Jupiter at 5 micrometers recorded at the Kuiper Airborne Observatory is used to determine upper limits to the column density of 19 molecules. The upper limits to the mixing ratios of SiH4, H2S, HCN, and simple hydrocarbons are discussed with respect to current models of Jupiter's atmosphere. These upper limits are compared to expectations based upon the solar abundance of the elements. This analysis permits upper limit measurements (SiH4), or actual detections (GeH4) of molecules with mixing ratios with hydrogen as low as 10 to the minus 9th power. In future observations at 5 micrometers the sensitivity of remote spectroscopic analyses should permit the study of constituents with mixing ratios as low as 10 to the minus 10th power, which would include the hydrides of such elements as Sn and As as well as numerous organic molecules.

Treffers, R. R.↗
NASA NTRS1978

Electrical structure and ionizable constituent measurements

In-situ stratospheric ions showed typical characteristics. A Krypton lamp created large numbers of additional ions of remarkably high mobility with a product of number density and ionization cross section of the ionizable constituent(s) greater than 10 cm to the 9th power per cm.

Hale, L. C.↗
NASA NTRS1979

Orbit design for solar and dual satellite occultation measurements of atmospheric constituents

Two types of satellite based occultation missions are considered for measuring atmospheric constituents. Nominal cases for each type are presented to demonstrate representative solutions to orbit design problems. For the solar occultation mode, large areas of the globe can be covered during a one year mission, but the measurements are limited to local dawn or dusk. For the dual satellite mode, with a laser aboard a second satellite to act as a source, diurnal coverage can be obtained at the expense of more complex systems and mission scenarios. In this mode, orbit pairs are selected which maintain their relative orbit plane geometry while their differing periods drive cyclic patterns of latitude coverage. A simulated one year solar occultation mission is used to illustrate one way of analyzing occultation data by averaging measurements within bands of constant latitude.

Brooks, D. R.↗
NASA NTRS1979

Possible effects of volcanic eruptions on stratospheric minor constituent chemistry

Although stratosphere penetrating volcanic eruptions have been infrequent during the last half century, periods have existed in the last several hundred years when such eruptions were significantly more frequent. Several mechanisms exist for these injections to affect stratospheric minor constituent chemistry, both on the long-term average and for short-term perturbations. These mechanisms are reviewed and, because of the sensitivity of current models of stratospheric ozone to chlorine perturbations, quantitative estimates are made of chlorine injection rates. It is found that, if chlorine makes up as much as 0.5 to 1% of the gases released and if the total gases released are about the same magnitude as the fine ash, then a major stratosphere penetrating eruption could deplete the ozone column by several percent. The estimate for the Agung eruption of 1963 is just under 1% an amount not excluded by the ozone record but complicated by the peak in atmospheric nuclear explosions at about the same time.

Stolarski, R. S.↗
NASA NTRS1979

Minor constituents in the stratosphere and mesosphere

A review of the research in minor constituents in the stratosphere and mesosphere, carried out between 1975 and 1978, is presented. Much of the theoretical research was done with the aid of one-dimensional models. Different aspects of these models are discussed. Measurements of the chlorofluoromethanes, hydrochloric acid, nitric oxide, nitrous oxide, and hydrogen oxide were conducted. It is noted that the hydrogen oxides are now assuming a larger role in stratospheric photochemistry than have been postulated before. The effect of water vapor and the hydrogen oxides on the overall chemistry of the stratosphere was investigated theoretically, along with the possible relationship between solar activity and atmospheric ozone. The mesosphere study included ozone, water vapor, nitric oxide, and odd nitrogen investigations.

Hudson, R. D.↗
NASA NTRS1979

Ionization frequencies for major thermospheric constituents as a function of solar cycle 21

Increases in the solar ultraviolet flux (wavelengths shorter than 1250A) over the past five years of rising solar activity have been larger than anticipated. This increase in UV flux dramatically affects the production of ionization of the various constituents in the thermosphere. Measurements of the solar UV flux by the Atmosphere Explorer satellites are used to determine ionization frequencies for the major thermospheric species for various dates exhibiting notably different levels of solar activity. For the convenience of users of such data, a reduced set of cross-section and flux data is presented for the wavelength range below 1027A, consisting of 37 wavelength intervals

Torr, M. R.↗
NASA NTRS1981

Preliminary feasibility analysis of a pressure modulator radiometer for remote sensing of tropospheric constituents

A pressure modulator radiometer operated in a nadir viewing mode from the top of a midlatitude summer model of the atmosphere was theoretically studied for monitoring the mean volumetric mixing ratio of carbon monoxide in the troposphere. The mechanical characteristics of the instrument on the Nimbus 7 stratospheric and mesospheric sounder experiment are assumed and CO is assumed to be the only infrared active constituent. A line by line radiative transfer computer program is used to simulate the upwelling radiation reaching the top of the atmosphere. The performance of the instrument is examined as a function of the mean pressure in and the length of the instrument gas correlation cell. Instrument sensitivity is described in terms of signal to noise ratio for a 10 percent change in CO mixing ratio. Sensitivity to mixing ratio changes is also studied. It is concluded that tropospheric monitoring requires a pressure modulator drive having a larger swept volume and producing higher compression ratios at higher mean cell pressures than the Nimbus 7 design.

Orr, H. D., III↗
NASA NTRS1981

Experiment K304: Studies of specific hepatic enzymes and liver constituents involved in the conversion of carbohydrates to lipids in rats exposed to prolonged space flight

The effects of space flight on the activities of 26 enzymes concerned with carbohydrate and lipid metabolism in hepatic tissue taken from male Wistar rats are investigated. These activities were measured in the various hepatic cell compartments, i.e., cytosol, mitochondria and microsomes. In addition, the levels of glycogen, total lipids, phospholipids, triglycerides, cholesterol, cholesterol esters, and the fatty acid composition of the rat livers were also examined and quantified. A similar group of ground-based rats treated in an identical manner served as controls. Both flight and synchronous control rats were sacrificed at three time intervals: R+0, 7-11 hours after recovery; R+6, after 6 days; R+6(S), after 6 days (having undergone 2-5 hour periods of fixed stress in a "backupward" position on days 0, 3, 4, 5 and 6) and R+29, after 29 days post-flight. Although most of the enzyme activities and the amounts of liver constituents studied were unaffected by the period of weightlessness, some significant differences were observed.

Abraham, S.↗
NASA NTRS1981

Stratospheric trace constituent profile retrievals using laser heterodyne radiometer IR limb sensing spectra

A retrieval technique for high resolution IR solar occultation limb sensing data is described for profiling stratospheric trace constituents. Remote measurement of ClO during sunset in the 24-45-km region with a 2-km height resolution is chosen as an example. Two types of instruments are considered: a laser heterodyne radiometer with line resolving spectral resolution and an interferometer spectrometer with a fixed slit width of 0.02/cm. It is pointed out that a multichannel approach is necessary with the heterodyne instrument for improved retrieval accuracy. The error analysis indicates the relative sizes of instrument noise and other sources of error in the retrieval of altitude profiles with high (2-km) vertical resolution.

Majumdar, A. K.↗
NASA NTRS1982

Long-term thermal degradation and alloying constituent effects on five boron/aluminum composites

Thermal exposure effects on the properties of five boron/aluminum composite systems were experimentally investigated. The composite systems were 49 volume percent boron fibers (203 micron diameter) in aluminum-alloy matrices 1100 Al, 2024 Al, 3003 Al, 5052 Al, and 6061 Al. Specimens were thermally exposed up to 10,000 hours at 500 K and 590 K, up to 500 hours at 730 K, and up to 10,000 hours at 500 K and 590 K, up to 500 hours at 730 K, and up to 2000 thermal cycles between 200 K and 590 K. Composite longitudinal and transverse tensile strengths, longitudinal compression strength, and in-plane shear strength were determined. None of the systems was severely degraded by exposure at 590 K. The best performing system was B-2024 Al. Effects of matrix alloys on degradation mechanisms were experimentally investigated. Composite specimens and individual fibers were metallurgically analyzed with a scanning electron microscope and an electron microprobe to determine failure characteristics, chemical element distribution, and reaction layer morphology. Alloying constituents were found to be affect the composite degradation mechanisms as follows: alloys containing iron, but without manganese as a stabilizer, caused increased low-temperature degradation; alloys containing magnesium, iron, or manganese caused increased degradation; and alloys containing copper caused increased fiber strength.

Olsen, G. C.↗
NASA NTRS1981

Meteorological and constituent data for January and February 1981

Balloon data consisting of a plot showing the mixing ratio of ozone partial pressure in micromillibors and temperature in degrees centigrade versus pressure altitude in millibars is presented. An accompanying tabulation of meteorological and constituent data is also presented. The total overburden was aquired by Dobson Spectrophotometer 72.

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NASA NTRS1981

Inversion technique for IR heterodyne sounding of stratospheric constituents from space platforms

The techniques which have been employed for inversion of IR heterodyne measurements for remote sounding of stratospheric trace constituents usually rely on either geometric effects based on limb-scan observations (i.e., onion peel techniques) or spectral effects by using weighting functions corresponding to different frequencies of an IR spectral line. An experimental approach and inversion technique are discussed which optimize the retrieval of concentration profiles by combining the geometric and the spectral effects in an IR heterodyne receiver. The results of inversions of some synthetic CIO spectral lines corresponding to solar occultation limb scans of the stratosphere are presented, indicating considerable improvement in the accuracy of the retrieved profiles. The effects of noise on the accuracy of retrievals are discussed for realistic situations.

Abbas, M. M.↗
NASA NTRS1981

Solar UV variability - Effects on stratospheric ozone, trace constituents and thermal structure

The effect of long-term (11-year solar cycle) solar UV variability on stratospheric chemical and thermal structure has been studied using a time-dependent one-dimensional model. Previous studies have suggested substantial variations in local and total ozone, and in stratospheric thermal structure from solar minimum to solar maximum. It is shown that significant variations also occur in some of the trace constituents. Members of the HOx family and N2O exhibit the largest variations, and these changes, if detected, may provide additional means of verifying the presence of solar UV variability and its effects. Some of the species show large phase differences with the assumed solar flux variation. The role of chemical and transport time constants on the time variations of the trace species is examined. Comparisons with reported ozone and temperature data show reasonable agreement for the period 1960 to 1972.

Natarajan, M.↗
NASA NTRS1980

Metallic particles in the glassy constituents of three lunar highland samples 65315, 67435 and 78235

Electron probe microanalysis and analytical electron microscopy techniques were employed to obtain structural and chemical analyses of metal particles in the size range of less than 1000 A and greater than 5 microns from the glassy constituents of 3 lunar highland samples 65315, 67435 and 78235. Most of the micron size metal particles in the glass coatings of the three samples are of meteoritic Co-Ni content. The Ni content of submicron metal often differs significantly from the micron size metal in the same glass. This difference can be explained by one of 3 reasons: (a) the presence of metal of different sizes and Ni contents in the rock prior to the shock event, (b) the presence of metal particles in the lunar soil of meteoritic or variable Ni content which were incorporated when the glass formed and (c) the production of submicroscopic Fe metal from the reduction of Fe(+2) in the shock produced melt.

Mehta, S.↗
NASA NTRS1983

Resolution of vertical mixing-ratio profiles of atmospheric constituents retrieved from solar spectra

The relationship between the uncertainty and the resolution of the mixing-ratio profiles of absorbing gases retrieved from simulated occultation data has been investigated by analyzing sets of absorber amounts, corresponding to a constituent with a constant vertical mixing-ratio profile, along atmospheric paths observed by instruments at 0, 30, and 500 km. The vertical resolution below the instrument is limited by the number of observations and the SNR; it degrades exponentially with height and is independent of the instrument altitude; it is nearly 50 times better than the resolution obtainable above the instrument. An estimate of the resolution obtained by analyzing line shapes is included for comparison.

Shaffer, W. A.↗
NASA NTRS1984

The photochemical time constants of minor constituents and their families in the middle atmosphere

A comprehensive formula is worked out for the photochemical time constant of minor constituents in the middle atmosphere. The formula is particularly useful for evaluating the time constants for families of some chemical species that are strongly coupled by rapid exchange reactions. Height profiles of photochemical time constants are calculated for individual species and their families based on the chemical reaction rate constants recommended in the recent WMO and JPL reports. Potential exchange reactions among various family members are discussed, and the effects of the choice of family membership on the time constant are evaluated.

Shimazaki, T.↗
NASA NTRS1984

Constituent Properties and Interrelationships

The requirements and recommendations of constituent properties and relationships are: (1) goals/requirement statement; (2) better operational definition of toughness; (3) assess limitations of current micromechanics models/procedures; (4) explicity assess currently known resin toughening mechanisms and determine their relative importance to matrix resins; (5) method to define the interphase region in situ; (6) assess thermodynamic compatibility of any new resin with the fiber; and (7) model polymer systems.

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