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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 433 records · Page 24
All sourcesNASA NTRSDOE OSTI
NASA NTRS2004

Observing Human-induced Linkages between Urbanization and Earth's Climate System

Urbanization is one of the extreme cases of land use change. Most of world s population has moved to urban areas. Although currently only 1.2% of the land is considered urban, the spatial coverage and density of cities are expected to rapidly increase in the near future. It is estimated that by the year 2025, 60% of the world s population will live in cities. Human activity in urban environments also alters atmospheric composition; impacts components of the water cycle; and modifies the carbon cycle and ecosystems. However, our understanding of urbanization on the total Earth-climate system is incomplete. Better understanding of how the Earth s atmosphere-ocean-land-biosphere components interact as a coupled system and the influence of the urban environment on this climate system is critical. The goal of the 2003 AGU Union session Human-induced climate variations on urban areas: From observations to modeling was to bring together scientists from interdisciplinary backgrounds to discuss the data, scientific approaches and recent results on observing and modeling components of the urban environment with the intent of sampling our current stand and discussing future direction on this topic. Herein, a summary and discussion of the observations component of the session are presented.

Shepherd, J. Marshall↗
NASA NTRS2010

Thermal Stability of a 4 Meter Primary Reflector for the Scanning Microwave Limb Sounder

We describe the fabrication and thermal-stability analysis and test of a composite demonstration model of the Scanning Microwave Limb Sounder (SMLS) primary reflector, having full 4m height and 1/3 the width planned for flight. SMLS is a space-borne heterodyne radiometer which will measure pressure, temperature and atmospheric constituents from thermal emission between 180 and 660 GHz. Current MLS instruments in low Earth orbit scan pencil-beam antennas (sized to resolve about one scale height) vertically over the atmospheric limb. SMLS, planned for the Global Atmospheric Composition Mission of the NRC Decadal Survey, adds azimuthal scanning for better horizontal and temporal resolution and coverage than typical orbit spacing provides. SMLS combines the wide scan range of the parabolic torus with unblocked offset Cassegrain optics. The resulting system is diffraction-limited in the vertical plane but highly astigmatic in the horizontal, having a beam aspect ratio [tilde operator]1:20. Symmetry about the nadir axis ensures that beam shape is nearly invariant over +/-65(white bullet) azimuth. The a feeds a low-noise SIS receiver whose FOV is swept over the reflector system by a small scanning mirror. Using finiteelement models of antenna reflectors and structure, we evaluate thermal deformations and the resulting optical performance for 4 orbital environments and isothermal soak. We compare deformations with photogrammetric measurements made during wide-range (ambient+[-97,+75](white bullet) C) thermal soak tests of the primary in a chamber. This range exceeds predicted orbital soak ranges by large factors, implying in-orbit thermal stability of 0.21(mu)m rms/(white bullet)C, which meets SMLS requirements.

Thermal stability tests↗
NASA NTRS2014

Scientific Rationale for Saturn's in Situ Exploration

Remote sensing observations meet some limitations when used to study the bulk atmospheric composition of the giant planets of our solar system. A remarkable example of the superiority of in situ probe measurements is illustrated by the exploration of Jupiter, where key measurements such as the determination of the noble gases׳ abundances and the precise measurement of the helium mixing ratio have only been made available through in situ measurements by the Galileo probe. This paper describes the main scientific goals to be addressed by the future in situ exploration of Saturn placing the Galileo probe exploration of Jupiter in a broader context and before the future probe exploration of the more remote ice giants. In situ exploration of Saturn's atmosphere addresses two broad themes that are discussed throughout this paper: first, the formation history of our solar system and second, the processes at play in planetary atmospheres. In this context, we detail the reasons why measurements of Saturn's bulk elemental and isotopic composition would place important constraints on the volatile reservoirs in the protosolar nebula. We also show that the in situ measurement of CO (or any other disequilibrium species that is depleted by reaction with water) in Saturn's upper troposphere may help constraining its bulk O/H ratio. We compare predictions of Jupiter and Saturn's bulk compositions from different formation scenarios, and highlight the key measurements required to distinguish competing theories to shed light on giant planet formation as a common process in planetary systems with potential applications to most extrasolar systems. In situ measurements of Saturn's stratospheric and tropospheric dynamics, chemistry and cloud-forming processes will provide access to phenomena unreachable to remote sensing studies. Different mission architectures are envisaged, which would benefit from strong international collaborations, all based on an entry probe that would descend through Saturn's stratosphere and troposphere under parachute down to a minimum of 10 bar of atmospheric pressure. We finally discuss the science payload required on a Saturn probe to match the measurement requirements.

Galileo↗
NASA NTRS1976

Evolution of the ionosphere

Studies were made of the electron density profiles at various stages of atmospheric evolution, with the assumption that the atmospheric composition has changed due to the gradual increase of oxygen while the nitrogen level has remained constant. The result of model calculations indicates that when the oxygen content is less than about 1% of the present earth's atmosphere level, the major ions in the F2 region will change from O(+) to N(+). The maximum number density of N(+) ions reaches approximately 10 million per cu cm because of the absence of a rapid loss mechanism for N(+). The height of the N(+) ion density peak is much lower than the height of the F2 layer peak of the current ionosphere.

Shimizu, M.↗
NASA NTRS1992

Chemical models of volcanic outgassing on Mars

During the MSATT workshop in Boulder, CO, several participants emphasized the importance of constraints on the composition and temporal evolution of outgassed volatiles on Mars. I present the results of some preliminary calculations that model the composition of volcanic gases as a function of temperature, pressure, oxygen fugacity, and quench function of temperature. These results can be used in combination with cosmochemical models for the accretion of Mars to assess the plausibility of different atmospheric compositions during the planet's early history.

Fegley, Bruce, Jr.↗
NASA NTRS2017

Exploration of Venus' Deep Atmosphere and Surface Environment

Venus formed in the same part of our solar system as Earth, apparently from similar materials. Although both planets are about the same size, their differences are profound. Venus and Earth experienced vastly different evolutionary pathways resulting in unexplained differences in atmospheric composition and dynamics, as well as in geophysical processes of the planetary surfaces and interiors. Understanding when and why the evolutionary pathways of Venus and Earth diverged is key to understanding how terrestrial planets form and how their atmospheres and surfaces evolve. Measurements made in situ, within the near-surface or surface environment, are critical to addressing unanswered questions. We have made substantial progress modernizing and maturing pressure vessel technologies to enable science operations in the high temperature and pressure near-surface/surfaceenvironment of Venus.

Venus Atmosphere↗
NASA NTRSDate not supplied

Solar Migrating Diurnal Tide in the Upper Mesosphere and Lower Thermosphere from SD-WACCM-X, Aura/MLS, and TIMED/SABER

Solar heating on the rotating Earth is a fundamental forcing of atmospheric tidal waves. The migrating diurnal tide, propagating from the troposphere to the upper mesosphere and lower thermosphere, is a large global disturbance that drives most of the daily variations in dynamics, thermal structures, chemistry, as well as atmospheric compositions. In this study, we present a comprehensive analysis of the (1,1) propagating diurnal tides derived from multi-year MLS and SABER observations, to characterize and better understand interannual and long-term tidal variability in the upper atmosphere. Although the (1,1) tide is driven by the solar heating, its interannual variations are largely determined by the internal variability of Earth’s climate system. The tidal amplitudes derived from MLS and SABER data agree well with each other in terms of monthly climatology and interannual variations, showing a consistent seasonal cycle and modulations from the Quasi Biennial Oscillation (QBO). The Ensemble Empirical Mode Decomposition (EEMD) analysis, employed to extract the low frequency variations, also reveals an ENSO-like (42 months) influence on tidal amplitudes in the upper mesosphere. While their (1,1) tidal amplitudes are less affected by the solar cycle, the mean mixing ratio of carbon monoxide (CO) and ozone (O3) is significantly modulated by the 11-year solar cycle due to their UV-dependent photochemistry.

mesosphere↗
NASA NTRS2008

Huygens Gas Chromatograph Mass Spectrometer Results from Titan

The Huygens Probe executed a successful entry, descent and impact on the Saturnian moon of Titan on January 14, 2005. Gas Chromatograph Mass Spectrometer (GCMS) instrument conducted isotopic and compositional measurements throughout the two and one half hour descent from 146 km altitude, and on the surface for 69 minutes until loss of signal from the orbiting Cassini spacecraft. The GCMS incorporated a quadrupole mass filter with a secondary electron multiplier detection system. The gas sampling system provided continuous direct atmospheric composition measurements and batch sampling through three gas chromatographic (GC) columns, a chemical scrubber and a hydrocarbon enrichment cell. The GCMS gas inlet was heated to prevent condensation, and to evaporate volatiles from the surface after impact. Data products from the GCMS included altitude profiles of the major atmospheric constituents dinitrogen (N2) and methane (CH4), isotope ratios of N-14/N-15, C-12/C-13, and D/H, mole fractions of radiogenic argon (Ar-40)and primordial argon Ar-36), and upper limits on the mole fractions of neon, krypton and xenon, which were found to be below the detection limit of the instrument or absent. Surface measurements confirmed the presence of ethane (C2H6) and cyanogen (C2N2). Later data products include the instrument response to surface outgassing of C2N2, C2H6, acetylene (C2H2),and carbon dioxide (CO2). More recent results include the detection of benzene (C6H6) and height profiles of molecular hydrogen (H2). Numerous other trace species evaporating from the surface were also identified using the GCMS data.

Niemann, Hasso↗
NASA NTRS2007

Huygens GCMS Results from Titan

The Huygens Probe executed a successful entry, descent and impact on the Saturnian moon of Titan on January 14, 2005. The Gas Chromatograph Mass Spectrometer (GCMS) instrument conducted isotopic and compositional measurements throughout the two and one half hour descent from 146 km altitude, and on the surface for 69 minutes until loss of signal from the orbiting Cassini spacecraft. The GCMS incorporated a quadrupole mass filter with a secondary electron multiplier detection system. The gas sampling system provided continuous direct atmospheric composition measurements and batch sampling through three gas chromatographic (GC) columns, a chemical scrubber and a hydrocarbon enrichment cell. The GCMS gas inlet was heated to prevent condensation, and to evaporate volatiles from the surface after impact. Data products from the GCMS included altitude profiles of the major atmospheric constituents dinitrogen (N2) and methane (CH4), isotope ratios of 14N/15N, 12C/13C, and D/H, mole fractions of radiogenic argon (40Ar) and primordial argon (36Ar), and upper limits on the mole fractions of neon, krypton and xenon, which were found to be absent. Surface measurements confirmed the presence of ethane (C2H6) and cyanogen (C2N2). Later data products expanded atmospheric profiles to include the surface response of C2N2. C2H6, acetylene (C2H2), and carbon dioxide (CO2). More recent results include the profiles of benzene (C6H6) and molecular hydrogen (H2). The GCMS data are being further analyzed to obtain higher precision results and to identify other trace species ion the atmosphere and evaporating from the surface.

Niemann, Hasso B.↗
NASA NTRS1976

Chemistry and spectroscopy of the Jovian atmosphere

A comprehensive review is given of the chemistry and spectroscopic studies of the Jovian atmosphere. Thermochemical equilibrium models for determining atmospheric composition are considered along with possible disequilibrating processes, and studies of the photochemistry of H2, CH4, NH3, H2S, and PH3 using the modeling methods are summarized. It is shown that photodissociation and advection are the major disequilibrating processes in Jupiter's atmosphere, that lightning and charged-particle bombardment are relatively minor factors in the planet's bulk chemistry, and that the existence of living organisms on the planet is highly improbable. Spectroscopic investigations of Jupiter are discussed, emphasizing recent observations of absorption bands due to CH4, NH3, H2, He, and D. Spectroscopic abundance determinations are examined for H2, HD, CH4, CH3D, NH3, C2H6, C2H2, and PH3. Upper limits are given for the abundances of several unobserved gases in the visible atmosphere, including H2S, HCl, SiH4, benzene, purines, pyrimidines, and their derivatives.

Prinn, R. G.↗
NASA NTRS1993

Multiorder etalon sounder (MOES) development and test for balloon experiment

The Fabry-Perot interferometer (FPI), with its high throughput and high spectral resolution has been used in the remote-sensing measurements of the earth's atmospheric composition, winds, and temperatures. The most recent satellite instruments include the Fabry-Perot interferometer flown on the Dynamics Explorer-2 (DE-2), the High Resolution Doppler Imager (HRDI), and the Cryogenic Limb Array Etalon Spectrometer (CLAES) flown on the Upper Atmosphere Research Satellite (UARS). These instruments measure the Doppler line profiles of the emission and absorption of certain atmospheric species (such as atomic oxygen) in the visible and infrared spectral region. The successful space flight of DE-FPI, HRDI, and CLAES on UARS demonstrated the extremely high spectral resolution and ruggedness of the etalon system for the remote sensing of earth and planetary atmospheres. Recently, an innovative FPI focal plane detection technique called the Circle-to-Line Interferometer Optical (CLIO) system was invented at the Space Physics Research Laboratory. The CLIO simplifies the FPI focal plane detection process by converting the circular rings or fringes into a linear pattern similar to that produced by a conventional spectrometer, while retaining the throughput advantage of the etalon interferometer. The combination of FPI and CLIO allows the development of more sensitive Fabry-Perot interferometers in the infrared for the remote sensing of the lower atmospheres of Earth and possibly other planets. The Multiorder Etalon Sounder (MOES), a combination of the rugged etalon and the CLIO, compares very favorably to other space-borne optical instruments in terms of performance versus complexity. The new instrument is expected to be rugged, compact, and very suitable for an operational temperature and moisture sounder. With this technique, the contamination of radiance measurements by emissions of other gases is also minimized. At the Space Physics Research Laboratory (SPRL), the MOES concept and laboratory experiments were worked on for the past several years. Both theoretical studies and laboratory prototype experiments showed that MOES is very competitive compared with other high resolution sounders in terms of complexity and performance and has great potential as a compact and rugged high resolution atmospheric temperature and trace species sounder from the polar platform or the geostationary platform. The logical next step is to convert our laboratory prototype to a balloon instrument, so that field test of MOES can be carried out to prove the feasibility and capability of this new technology. Some of the activities related to the development of MOES for a possible balloon flight demonstration are described. Those research activities include the imaging quality study on the CLIO, the design and construction of a MOES laboratory prototype, the test and calibration of the MOES prototype, and the design of the balloon flight gondola.

Hays, Paul B.↗
NASA NTRS2001

Projected Impact of Climate Change on the Energy Budget of the Arctic Ocean by a Global Climate Model

The annual energy budget of the Arctic Ocean is characterized by a net heat loss at the air-sea interface that is balanced by oceanic heat transport into the Arctic. The energy loss at the air-sea interface is due to the combined effects of radiative, sensible, and latent heat fluxes. The inflow of heat by the ocean can be divided into two components: the transport of water masses of different temperatures between the Arctic and the Atlantic and Pacific Oceans and the export of sea ice, primarily through Fram Strait. Two 150-year simulations (1950-2099) of a global climate model are used to examine how this balance might change if atmospheric greenhouse gases (GHGs) increase. One is a control simulation for the present climate with constant 1950 atmospheric composition, and the other is a transient experiment with observed GHGs from 1950 to 1990 and 0.5% annual compounded increases of CO2 after 1990. For the present climate the model agrees well with observations of radiative fluxes at the top of the atmosphere, atmospheric advective energy transport into the Arctic, and surface air temperature. It also simulates the seasonal cycle and summer increase of cloud cover and the seasonal cycle of sea-ice cover. In addition, the changes in high-latitude surface air temperature and sea-ice cover in the GHG experiment are consistent with observed changes during the last 40 and 20 years, respectively. Relative to the control, the last 50-year period of the GHG experiment indicates that even though the net annual incident solar radiation at the surface decreases by 4.6 W(per square meters) (because of greater cloud cover and increased cloud optical depth), the absorbed solar radiation increases by 2.8 W(per square meters) (because of less sea ice). Increased cloud cover and warmer air also cause increased downward thermal radiation at the surface so that the net radiation into the ocean increases by 5.0 Wm-2. The annual increase in radiation into the ocean, however, is compensated by larger increases in sensible and latent heat fluxes out of the ocean. Although the net energy loss from the ocean surface increases by 0.8 W (per square meters), this is less than the interannual variability, and the increase may not indicate a long-term trend. The seasonal cycle of heat fluxes is significantly enhanced. The downward surface heat flux increases in summer (maximum 2 of 19 W per square meters or 23% in June) while the upward heat flux increases in winter (maximum of 16 W per square meters or 28% in November). The increased downward flux in summer is due to a combination of increases in absorbed solar and thermal radiation and smaller losses of sensible and latent heat. The increased heat loss in winter is due to increased sensible and latent heat fluxes, which in turn are due to reduced sea-ice cover. On the other hand, the seasonal cycle of surface air temperature is damped, as there is a large increase in winter temperature but little change in summer.

Miller, James R.↗
NASA NTRS2003

Simulation of Prebiotic Processing by Comet and Meteoroid Impact: Implications for Life on Early Earth and Other Planets

We develop a reacting flow model to simulate the shock induced chemistry of comets and meteoroids entering planetary atmospheres. Various atmospheric compositions comprising of simpler molecules (i.e., CH4, CO2, H2O, etc.) are investigated to determine the production efficiency of more complex prebiotic molecules as a function of composition, pressure, and entry velocity. The possible role of comets and meteoroids in creating the inventory of prebiotic material necessary for life on Early Earth is considered. Comets and meteoroids can also introduce new materials from the Interstellar Medium (ISM) to planetary atmospheres. The ablation of water from comets, introducing the element oxygen into Titan's atmosphere will also be considered and its implications for the formation of organic and prebiotic material.

Dateo, Christopher E.↗
NASA NTRS2005

In-situ exploration of Venus on a global scale : direct measurements of origins and evolution, meterology, dynamics, and chemistry by a long-duration aerial science station

Drifting in the strong winds of Venus under benign Earth-like temperature and pressure conditions, an instrumented balloon-borne science station presents a viable means to explore, in-situ, the Venusian atmosphere on a global scale. Flying over the ground at speeds exceeding 240 km/hour while floating in the Venusian skies near 55 km altitude for several weeks, such an aerostat can conduct a 'world tour' of our neighboring planet, as it circumnavigates the globe multiple times during its flight from equatorial to polar latitudes. Onboard science sensors can repeatedly and directly sample gas compositions, atmospheric pressures and temperatures and cloud particle properties, giving unprecedented insight into the chemical processes occurring within the sulfuric clouds. Additionally, interferometric tracking via Earth-based radio observatories can yield positions and windspeeds to better than 10 cm/sec over one-hour periods, providing important information for understanding the planet's meridional circulation and enigmatic zonal super-rotation, as well as local dynamics associated with meteorological processes. As well, hundreds of GCMS spectra collected during the flight can provide measurements of noble gas compositions and their isotopes with unprecedented accuracy, thereby enabling fundamental new insights into Venus's origin and evolution.

Venus↗
NASA NTRS1977

Occultation of Epsilon Geminorum by Mars. II - The structure and extinction of the Martian upper atmosphere

The occultation of Epsilon Geminorum by Mars on April 8, 1976, was observed at three wavelengths and 4-ms time resolution with the 91-cm telescope aboard NASA's G. P. Kuiper Airborne Observatory. Temperature, pressure, and number-density profiles of the Martian atmosphere were obtained for both the immersion and emersion events. Within the altitude range 50-80 km above the mean surface, the mean temperature is about 145 K, and the profiles exhibit wavelike structures with a peak-to-peak amplitude of 35 K and a vertical scale of about 20 km. The ratio of the refractivity of the atmosphere at 4500 A and 7500 A is consistent with the atmospheric composition measured by Viking 1. From the 'central flash' - a bright feature in the light curve midway between immersion and emersion - an optical depth at 4500 A of 3.3 + or - 1.7 per km atm (about 0.23 per equivalent Martian air mass) is found for the atmosphere about 25 km above the mean surface near the south polar region. This large value and its weak wavelength dependence rule out Rayleigh scattering as the principal cause of the observed extinction.

Elliot, J. L.↗
NASA NTRS1982

Seasonal variations of the high-latitude F region for strong convection

A plasma convection model is combined with an ionospheric-atmospheric composition model in order to study the seasonal variations of the high-latitude F region for geomagnetic conditions leading to strong convection. In a model calculation, a field tube of plasma is followed as it moves along a convection trajectory through a moving neutral atmosphere. Altitude profiles of the ion densities are obtained by solving the appropriate continuity, momentum, and energy equations including numerous high-latitude processes. It is found that the high-latitude ionosphere exhibits a significant UT variation both during the winter and summer. In general, the electron density at high-latitudes is lower in winter than in summer. In both summer and winter, the major region of low electron density is associated with the 'main' or mid-latitude' trough.

Sojka, J. J.↗
NASA NTRS1996

Isotopic Analysis and Evolved Gases

Precise measurements of the chemical, elemental, and isotopic composition of planetary surface material and gases, and observed variations in these compositions, can contribute significantly to our knowledge of the source(s), ages, and evolution of solar system materials. The analyses discussed in this paper are mostly made by mass spectrometers or some other type of mass analyzer, and address three broad areas of interest: (1) atmospheric composition - isotopic, elemental, and molecular, (2) gases evolved from solids, and (3) solids. Current isotopic data on nine elements, mostly from in situ analysis, but also from meteorites and telescopic observations are summarized. Potential instruments for isotopic analysis of lunar, Martian, Venusian, Mercury, and Pluto surfaces, along with asteroid, cometary and icy satellites, surfaces are discussed.

Swindle, Timothy D.↗