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NASA NTRS2003

Impact of Defect Distributions on the Reliability of Structural Materials

The purpose of this study is to develop a probabilistic model to estimate the fatigue life of gas turbine disks made of powder superalloy metals. Such metals are known to have high strength and ductility under extremely high temperatures and known to have high fatigue lives. However, despite the high quality controls instituted during metal processing, sufficiently high numbers of ceramic inclusions materialize within the metal matrix creating weak links that lead to reduced fatigue lives. To study the effect of such ceramic inclusions on the fatigue life of gas turbine disks, an experimental program has been initiated at the NASA Glenn Research. In this phase of the study, a statistical analysis of the test results is undertaken which served as the basis of the probabilistic simulation model. The study is a part of the Crack Resistant Disk Materials task within the Ultra Safe Propulsion Project.

Ghosn, Michel J.↗
NASA NTRS2004

An Environmental for Hardware-in-the-Loop Formation Navigation and Control

Recent interest in formation flying satellite systems has spurred a considerable amount of research in the relative navigation and control of satellites. Development in this area has included new estimation and control algorithms as well as sensor and actuator development specifically geared toward the relative control problem. This paper describes a simulation facility, the Formation Flying Test Bed (FFTB) at NASA Goddard Space Flight Center, which allows engineers to test new algorithms for the formation flying problem with relevant GN&C hardware in a closed loop simulation. The FFTB currently supports the inclusion of GPS receiver hardware in the simulation loop. Support for satellite crosslink ranging technology is at a prototype stage. This closed-loop, hardware inclusive simulation capability permits testing of navigation and control software in the presence of the actual hardware with which the algorithms must interact. This capability provides the navigation or control developer with a perspective on how the algorithms perform as part of the closed-loop system. In this paper, the overall design and evolution of the FFTB are presented. Each component of the FFTB is then described. Interfaces between the components of the FFTB are shown and the interfaces to and between navigation and control software are described. Finally, an example of closed-loop formation control with GPS receivers in the loop is presented.

Burns, Rich↗
NASA NTRS2004

Diffraction and imaging study of imperfections of crystallized lysozyme with coherent X-rays

Phase-contrast X-ray diffraction imaging and high-angular-resolution diffraction combined with phase-contrast radiographic imaging were employed to characterize defects and perfection of a uniformly grown tetragonal lysozyme crystal in the symmetric Laue case. The full-width at half-maximum (FWHM) of a 4 4 0 rocking curve measured from the original crystal was approximately 16.7 arcsec and imperfections including line defects, inclusions and other microdefects were observed in the diffraction images of the crystal. The observed line defects carry distinct dislocation features running approximately along the <1 1 0> growth front and have been found to originate mostly in a central growth area and occasionally in outer growth regions. Inclusions of impurities or formations of foreign particles in the central growth region are resolved in the images with high sensitivity to defects. Slow dehydration led to the broadening of a fairly symmetric 4 4 0 rocking curve by a factor of approximately 2.6, which was primarily attributed to the dehydration-induced microscopic effects that are clearly shown in X-ray diffraction images. The details of the observed defects and the significant change in the revealed microstructures with drying provide insight into the nature of imperfections, nucleation and growth, and the properties of protein crystals.

Muramidase/chemistry↗
NASA NTRS2004

Chondrites and the Protoplanetary Disk, Part 1

The papers discussed the following: The Formation Process of Adhering and Consorting Compound Chondrules Inferred Their Petrology and Major-Element Composition. The Prospect of High-Precision Pb Isotopic Dating of Meteorites. Evolution of UV-Irradiated Protoplanetary Disks. A Model for the Formation of E Chondrites. Oxygen Isotopic Diffusion and Exchange Experiments on Olivine and Chondrule Melts: Preliminary Results. Shock Heating: Origin of Shock Waves in the Protoplanetary Disk. Thermal Structures of Protoplanetary Disks. Meteoritical Astrophysics: A New Subdiscipline. Origin and Thermal History of FeNi-Metal in Primitive Chondrites. The Collisions of Chondrules Behind Shock Waves. Primary Signatures of the Nebular Dust Preserved in Accretionary Rims and Matrices of CV Chondrites. History of Thermally Processed Solids in the Protoplanetary Disk: Reconciling Theoretical Models and Meteoritical. Evidence Evaporation and Condensation During CAI and Chondrule Formation. Shock Heating: Effects on Chondritic Material. Rhounite-bearing Inclusions E201 and E202 from Efremovka: Constraints from Trace. Element Measurements Element Mapping in Anhydrous IDPs: Identification of the Host Phases of Major/Minor Elements as a Test of Nebula Condensation Models. Theoretical Studies of Disk Evolution Around Solar Mass Stars. Chemical Effects of High-Temperature Processing of Silicates. I-Xe and the Chronology of the Early Solar System. The Effects of X-Rays on the Gas and Dust in Young Stellar Objects. Origin of Short-lived Radionuclides in the Early Solar System. On Early Solar System Chronology: Implications of an Initially Heterogeneous Distribution of Short-lived Radionuclides. The Origin of Short-lived Radionuclides and Early Solar System Irradiation. Disequilibrium Melting and Oxygen Isotope Exchange of CAIs and Chondrules in the Solar Nebula. Mineralogy and Chemistry of Fine-grained Matrices, Rims, and Dark Inclusions in the CR Carbonaceous Chondrites Acfer/El Djouf 001 and the Ungrouped Carbonaceous Chondrites Acfer 094 and Adelaide. Oxygen Isotopes of Aluminum-rich Chondrules from Unequilibrated Enstatite Chondrites.

Source record↗
NASA NTRS2004

Meteoritical Astrophysics: A New Subdiscipline

A recent remarkable discovery by Katharina Lodders showed that the abundances of extinct radioactivities (relative to reference nuclei) in chondrites, achondrites, and irons are proportional to the squares of their mean lives, whereas no such abundance-mean life relationship is apparent for the data of calcium-aluminum rich inclusions (CAIs) and a variety of other inclusion types. In this talk I shall interpret these results in terms of galactic and solar nebula processes. The first step in organizing the data for interpretation is to require that both the abundance of the extinct radioactivity (as measured by its decay product abundance) and that of the reference nuclide should have the same nucleosynthesis history, or else that a correction to the ratio be made to compensate for the ratio of the two different production processes. The striking feature of this diagram is that the lower edge of the data (the Lodders Line) is remarkably straight; most of the data are derived from chondrites; and its slope on the log-log diagram is two. So the extinct radioactivities are present in proportion to the square of their mean lives. All the other data lie above the Lodders line in this diagram; the sources of that data are in general somewhat larger particles than those that have contributed to the Lodders Line. A straight relationship between abundances of extinct radioactivities

Cameron, A. G. W.↗
NASA NTRS2004

Chondrites and the Protoplanetary Disk, Part 3

Contents include the following: Ca-, Al-Rich Inclusions and Ameoboid Olivine Aggregates: What We Know and Don t Know About Their Origin. Aluminium-26 and Oxygen Isotopic Distributions of Ca-Al-rich Inclusions from Acfer 214 CH Chondrite. The Trapping Efficiency of Helium in Fullerene and Its Implicatiion to the Planetary Science. Constraints on the Origin of Chondritic Components from Oxygen Isotopic Compositions. Role of Planetary Impacts in Thermal Processing of Chondrite Materials. Formation of the Melilite Mantle of the Type B1 CAIs: Flash Heating or Transport? The Iodine-Xenon System in Outer and Inner Portions of Chondrules from the Unnamed Antarctic LL3 Chondrite. Nucleosynthesis of Short-lived Radioactivities in Massive Stars. The Two-Fluid Analysis of the Kelvin-Helmholtz Instability in the Dust Layer of a Protoplanetary Disk: A Possible Path to the Planetesimal Formation Through the Gravitational Instability. Shock-Wave Heating Model for Chonodrule Formation: Heating Rate and Cooling Rate Constraints. Glycine Amide Hydrolysis with Water and OH Radical: A Comparative DFT Study. Micron-sized Sample Preparation for AFM and SEM. AFM, FE-SEM and Optical Imaging of a Shocked L/LL Chondrite: Implications for Martensite Formation and Wave Propagation. Infrared Spectroscopy of Chondrites and Their Components: A Link Between Meteoritics and Astronomy? Mid-Infrared Spectroscopy of CAI and Their Mineral Components. The Origin of Iron Isotope Fractionation in Chondrules, CAIs and Matrix from Allende (CV3) and Chainpur (LL3) Chondrites. Protoplanetary Disk Evolution: Early Results from Spitzer. Kinetics of Evaporation-Condensation in a Melt-Solid System and Its Role on the Chemical Composition and Evolution of Chondrules. Oxygen Isotope Exchange Recorded Within Anorthite Single Crystal in Vigarano CAI: Evidence for Remelting by High Temperature Process in the Solar Nebula. Chondrule Forming Shock Waves in Solar Nebula by X-Ray Flares. Organic Globules with Anormalous Nitrogen Isotopic Compositions in the Tagish Lake Meteorite: Products of Primitive Organic Reactions. Yet Another Chondrule Formation Scenario. CAIs are Not Supernova Condensates. Microcrystals and Amorphous Material in Comets and Primitive Meteorites: Keys to Understanding Processes in the Early Solar System. A Nearby Supernova Injected Short-lived Radionuclides into Our Protoplanetary Disk. REE+Y Systematics in CC and UOC Chondrules. Meteoritic Constraints on Temperatures, Pressures, Cooling Rates, Chemical Compositions, and Modes of Condensation in the Solar Nebula. The I-Xe Record of Long Equilibration in Chondrules from the Unnamed Antarctic Meteorite L3/LL3. Early Stellar Evolution.

Source record↗
NASA NTRS2004

Chondrites and the Protoplanetary Disk, Part 2

Contents include the following: On the Dynamical Evolution of a Nebula and Its Effect on Dust Coagulation and the Formation of Centimeter-sized Particles. The Mineralogy and Grain Properties of the Disk Surfaces in Three Herbig Ae/Be Stars. Astrophysical Observations of Disk Evolution Around Solar Mass Stars. The Systematic Petrology of Chondrites: A Consistent Approach to Assist Classification and Interpretation. Understanding Our Origins: Formation of Sun-like Stars in H II Region Environments. Chondrule Crystallization Experiments. Formation of SiO2-rich Chondrules by Fractional Condensation. Refractory Forsterites from Murchison (CM2) and Yamato 81020 (CO3.0) Chondrites: Cathodoluminescence, Chemical Compositions and Oxygen Isotopes. Apparent I-Xe Cooling Rates of Chondrules Compared with Silicates from the Colomera Iron Meteorite. Chondrule Formation in Planetesimal Bow Shocks: Physical Processes in the Near Vicinity of the Planetesimal. Genetic Relationships Between Chondrules, Rims and Matrix. Chondrite Fractionation was Cosmochemical; Chondrule Fractionation was Geochemical. Chondrule Formation and Accretion of Chondrite Parent Bodies: Environmental Constraints. Amoeboid Olivine Aggregates from the Semarkona LL3.0 Chondrite. The Evolution of Solids in Proto-Planetary Disks. New Nickel Vapor Pressure Measurements: Possible Implications for Nebular Condensates. Chemical, Mineralogical and Isotopic Properties of Chondrules: Clues to Their Origin. Maximal Size of Chondrules in Shock-Wave Heating Model: Stripping of Liquid Surface in Hypersonic Rarefied Gas Flow. The Nature and Origin of Interplanetary Dust: High Temperature Components. Refractory Relic Components in Chondrules from Ordinary Chondrites. Constraints on the Origin of Chondrules and CAIs from Short-lived and Long-lived Radionuclides. The Genetic Relationship Between Refractory Inclusions and Chondrules. Contemporaneous Chondrule Formation Between Ordinary and Carbonaceous Chondrites. Chondrules and Isolated Grains in the Fountain Hills Bencubbinite. Implications of Chondrule Formation in a Gas of Solar Composition. Implications of Meteoritic Cl-36 Abundance for the Origin of Short-lived Radionuclides in the Early Solar System. Size Sorting and the Chondrule Size Spectrum. Comparative Study of Refractory Inclusions from Different Groups of Chondrites. In Situ Investigation of Mg Isotope Distributions in an Allende CAI by Combined LA-ICPMS and SIMS Analyses Photochemical Speciation of Oxygen Isotopes in the Solar Nebula.

Source record↗
NASA NTRS2005

Ar-Ar and I-Xe Ages of Caddo County and Thermal History of IAB Iron Meteorites

Inclusions in IAB iron meteorites include non-chondritic silicate and those with more primitive chondritic silicate composition. Coarse-grained gabbroic material rich in plagioclase and diopside occurs in the Caddo County IAB iron meteorite and represents a new type of chemically differentiated, extra-terrestrial, andesitic silicate. Other parts of Caddo contain mostly andesitic material. Caddo thus exhibits petrologic characteristics of parent body metamorphism of a chondrite-like parent and inhomogeneous segregation of melts. Proposed IAB formation models include parent body partial melting and fractional crystallization or incomplete differentiation due to internal heat sources, and impact/induced melting and mixing. Benedix et al. prefer a hybrid model whereby the IAB parent body largely melted, then underwent collisional breakup, partial mixing of phases, and reassembly. Most reported 129I- Xe-129 ages of IABs are greater than 4.56 Gyr and a few are greater than or = 4.567 Gyr. These oldest ages exceed the 4.567 Gyr Pb-Pb age of Ca, Al-rich inclusions in primitive meteorites,

Bogard, Donald D.↗
NASA NTRS2005

Li, B - Behavior in Lunar Basalts During Shock and Thermal Metamorphism: Implications for H2O in Martian Magmas

Introduction: The water-content of Martian magmas is a topic of debate among researchers. Some Martian basalts are characterized with melt inclusions of biotite, apatite and amphibole; phases typically associated with hydration reactions on Earth [1-3]. However, the H-content of melt inclusions from these basalts is low, and bulk-rock H2O-contents range from a meager 0.013 to 0.035 wt. % in Shergotty [4]. Nonetheless, researchers note that low present-day water contents do not preclude a once hydrous past [5]. Since light lithophile elements (LLE), such as Li and B, partition into aqueous fluids at T > 350 C, workers proposed that Li-B depletions in pyroxene rims of Nakhlite and Shergottite basalts reflect the loss of several weight percent water from Martian magmas during crystallization [6]. Since similar depletions were observed in pyroxene rims from completely dry lunar basalts, it is likely that alternative mechanisms also contribute to the distribution of elements such as Li and B [7]. Given that many Martian basalts have experienced considerable shock pressures (15-45 GPa), it is possible that shock and subsequent thermal metamorphism may have influenced the volatile element records of these basalts [8]. In order to better understand the distribution of Li and B, we are studying the effects of crystal chemistry, shock pressure, and thermal metamorphism in pyroxenes from lunar basalts. Below, we discuss results from experimentally shocked and thermally metamorphosed Apollo 11, 10017 (A-11) and Apollo 17, 75035 (A-17) basalts.

Chaklader, Johny↗
NASA NTRS2005

Olivine and Ca-Phosphate in the Diogenites Manegaon and Roda

The textural relationships between the different primary minerals in igneous rocks provide one of the most fundamental pieces of evidence available for inferring the crystallization history of their parent magmas. Unfortunately, the high degree of brecciation that characterizes most diogenites, along with the low modal abundance and small grain sizes of minerals other than orthopyroxene, combine to make identifying and interpreting such textural relationships extremely difficult in this class of meteorites. A few descriptions of primary igneous contacts between orthopyroxene and chromite, troilite, and to a lesser extent, olivine in diogenites have been provided in the literature. In addition to these, in previous work, our research group has characterized several types of igneous contacts between Ca-pyroxene, plagioclase and orthopyroxene in the Bilanga diogenite. We have also described primary igneous inclusions of troilite + kamacite + chromite + Ca-pyroxene +/- Ca-phosphate in orthopyroxene (i.e. Metal/Troilite- Ball inclusions) in the diogenites Bilanga, Manegaon, Johnstown, Roda, Shalka, and Tatahouine. However, for the most part, detailed data on igneous textural relations between minerals other than orthopyroxene in diogenites are still sparse. Of the diogenite samples that we have examined,

Domanik, K. J.↗
NASA NTRS2005

Lunar and Planetary Science XXXVI, Part 20

The topics include: 1) Virtual Reality Technology as a Tool to Enhance Collaboration Between Space Exploration and Public Outreach: The Case Using the Mars Exploration Rover Images; 2) Atmospheric Electron-induced X-Ray Spectrometer (AEXS) Instrument Development; 3) Impact of Low Thermal Conductivity Layers on the Bulk Conductivity of a Martian Crustal Column; 4) Impacting Classroom Teachers Through Long-Term Professional Development; 5) Oxygen, Ca, and Ti Isotopic Compositions of Hibonite-bearing Inclusions; 6) Phenomenological Excitation Functions of Xe Isotopes with Protons on Nuclei of Cs, La and Ce; 7) Double-Diffusive Convection and Other Modes of Salinity-modulated Heat and Material Transport in Europa s Ocean; 8) Slope Morphologies of the Hellas Mensae Constructs, Eastern Hellas Planitia, Mars; 9) Development of Polygonal Thermal Contraction Patterns in a South Polar Trough, Mars 3 Years of Observations; 10) Martian Relevance of Dehydration and Rehydration in the Mg-Sulfate System; 11) Formation of Martian Volcanic Provinces by Lower Mantle Flushing? 12) Can Glasses Help Us to Unravel the Origin of Barred Olivine Chondrules? 13) Loki Patera: A Magma Sea Story; 14) Compositions of Partly Altered Olivine and Replacement Serpentine in the CM2 Chondrite QUE93005; 15) Model of Light Scattering by Lunar Regolith at Moderate Phase Angles: New Results; 16) Radiation Resistance of a Silicone Polymer Grease Based Regolith Collector for the HERA Near-Earth Asteroid Sample Return Mission; 17) Analysis of the Tectonic Lineaments in the Ganiki Planitia (V14) Quadrangle, Venus; 18) Nanometer-sized Diamonds from AGB Stars; 19) Quantifying Exact Motions Along Lineaments on Europa; 20) Geometry of Thrust Faults Beneath Amenthes Rupes, Mars; 21) Mapping of the Physical Characteristics and Mineral Composition of a Superficial Layer of the Moon or Mars and Ultra-Violet Polarimetry from the Orbital Station; 22) Negative Searches for Evidence of Aqueous Alteration on Asteroid Surfaces; 23) What Processes Have Shaped Basalt Boulders on Earth and Mars? Studies of Feature Persistence Using Facet Mapping and Fractal Analysis; 24) The Popigai Fluidizites: Dense Water Inclusions in Lechatelierite; Evidence for Shock-generated Carbonate and Hydrous Silicate Melts; 25) Missing Xenon Problem and Climate of the Early Earth; and 26) More on Magnetic Spectra from Correlated Crustal Sources on Mars

Source record↗
NASA NTRS2006

Precipitation links (PrecipLinks) - a prototype directory for precipitation information

This poster describes a web directory of research oriented precipitation links. In this era of sophisticated search engines and web agents, it might seem counterproductive to establish such a directory of links. However, entering precipitation into a search engine like google will yield over one million hits. To further exacerbate this situation many of the returned links are dead, duplicates of other links, incomplete, or only marginally related to research precipitation or even the broader precipitation area. Sometimes connecting the linked URL causes the browser to lose context and not be able to get back to the original page. Even using more sophisticated search engines query parameters or agents while reducing the overall return doesn't eliminate all of the other issues listed. As part of the development of the measurement-based Precipitation Processing System (PPS) that will support Tropical Rainfall Measuring Mission (TRMM) version 7 reprocessing and the Global Precipitation Measurement (GPM) mission a precipitation links (PrecipLinks) facility is being developed. PrecipLinks is intended to share locations of other sites that contain information or data pertaining to precipitation research. Potential contributors can log-on to the PrecipLinks website and register their site for inclusion in the directory. The price for inclusion is the requirement to place a link back to PrecipLinks on the webpage that is registered. This ensures that users will be able to easily get back to PrecipLinks regardless of any context issues that browsers might have. Perhaps more importantly users while visiting one site that they know can be referred to a location that has many others sites with which they might not be familiar. PrecipLinks is designed to have a very flat structure. This poster summarizes these categories (information, data, services) and the reasons for their selection. Providers may register multiple pages to which they wish to direct users. However, each page may be attached to only one of these categories. Each page to which they refer users will also have a return link to PrecipLinks. The poster describes the operation of the system both the automated and the human processes. It also provides images for the various steps in the registration and use.

Velanthapillia, Balendran↗
NASA NTRS1995

(abstract) A Polarimetric Model for Effects of Brine Infiltrated Snow Cover and Frost Flowers on Sea Ice Backscatter

A polarimetric scattering model is developed to study effects of snow cover and frost flowers with brine infiltration on thin sea ice. Leads containing thin sea ice in the Artic icepack are important to heat exchange with the atmosphere and salt flux into the upper ocean. Surface characteristics of thin sea ice in leads are dominated by the formation of frost flowers with high salinity. In many cases, the thin sea ice layer is covered by snow, which wicks up brine from sea ice due to capillary force. Snow and frost flowers have a significant impact on polarimetric signatures of thin ice, which needs to be studied for accessing the retrieval of geophysical parameters such as ice thickness. Frost flowers or snow layer is modeled with a heterogeneous mixture consisting of randomly oriented ellipsoids and brine infiltration in an air background. Ice crystals are characterized with three different axial lengths to depict the nonspherical shape. Under the covering multispecies medium, the columinar sea-ice layer is an inhomogeneous anisotropic medium composed of ellipsoidal brine inclusions preferentially oriented in the vertical direction in an ice background. The underlying medium is homogeneous sea water. This configuration is described with layered inhomogeneous media containing multiple species of scatterers. The species are allowed to have different size, shape, and permittivity. The strong permittivity fluctuation theory is extended to account for the multispecies in the derivation of effective permittivities with distributions of scatterer orientations characterized by Eulerian rotation angles. Polarimetric backscattering coefficients are obtained consistently with the same physical description used in the effective permittivity calculation. The mulitspecies model allows the inclusion of high-permittivity species to study effects of brine infiltrated snow cover and frost flowers on thin ice. The results suggest that the frost cover with a rough interface significantly increases the backscatter from thin saline ice and the polarimetric signature becomes closer to the isotropic characteristics. The snow cover also modifies polarimetric signatures of thin sea ice depending on the snow mixture and the interface condition.

thin sea ice radar backscatter frost flowers snow ↗
NASA NTRS2007

Liquid Metal Pump Technologies for Nuclear Surface Power

Multiple liquid metal pump options are reviewed for the purpose of determining the technologies that are best suited for inclusion in a nuclear reactor thermal simulator intended to test prototypical space nuclear system components. Conduction, induction, and thermoelectric electromagnetic pumps are evaluated based on their performance characteristics and the technical issues associated incorporation into a reactor system. The thermoelectric electromagnetic pump is recommended for inclusion in the present system based on favorable quantitative and qualitative measures relative to the other options under consideration.

Polzin, Kurt A.↗
NASA NTRS2007

Petrology and Geochemistry of New Ureilites and Ureilite Genesis

Ureilites are C-bearing, basalt-depleted olivine+pyroxene achondrites from a differentiated asteroid. The group is heterogeneous, exhibiting ranges in O isotopic composition, Fe/Mg, Fe/Mn, pyx/ol, siderophile and lithophile trace element content, and C content and isotopic composition [1]. Some of these characteristics are nebular in origin; others were strongly overprinted by asteroidal igneous processes. The consensus view is that most ureilites are melt-residues, but some are partial cumulates or have interacted with a melt [1,2]. An "unroofing" event occurred while the parent asteroid was hot that froze in mineral core com-positions and resulted in FeO reduction at olivine grain margins. We have studied several new ureilites, but will focus here on two anomalous stones; LAR 04315 and NWA 1241. LAR 04315 is texturally unusual. It contains olivine with angular subdomains, and low-Ca pyroxene riddled with wormy inclusions of metal+troilite, graphite, and possibly other phases, and irregular inclusions of high-Ca pyroxene. Reduction occurred along olivine grain margins and internal fractures, but not along subdomain boundaries. Although texturally odd, LAR 04351 is a typical ureilite in mineral and bulk composition. The olivine is Fo80.8 and falls on the ureilite Fe/Mn-Fe/Mg trend. Its olivine composition falls within the range of the majority of ureilites, and it is typical of these ureilites in bulk rock lithophile and siderophile element contents.

Mittlefehldt, David W.↗
NASA NTRS2007

Liquid-Metal Pump Technologies for Nuclear Surface Power

Multiple liquid-metal pump options are reviewed for the purpose of determining the technologies that are best suited for inclusion in a nuclear reactor thermal simulator intended to test prototypical space nuclear system components. Conduction, induction, and thermoelectric electromagnetic pumps are evaluated based on their performance characteristics and the technical issues associated with incorporation into a reactor system. The thermoelectric pump is recommended for inclusion in the planned system at NASA MSFC based on its relative simplicity, low power supply mass penalty, flight heritage, and the promise of increased pump efficiency over earlier flight pump designs through the use of skutterudite thermoelectric elements.

Polzin, K. A.↗
NASA NTRS2007

Aerosol Absorption and Radiative Forcing

We present a comprehensive examination of aerosol absorption with a focus on evaluating the sensitivity of the global distribution of aerosol absorption to key uncertainties in the process representation. For this purpose we extended the comprehensive aerosol-climate model ECHAM5-HAM by effective medium approximations for the calculation of aerosol effective refractive indices, updated black carbon refractive indices, new cloud radiative properties considering the effect of aerosol inclusions, as well as by modules for the calculation of long-wave aerosol radiative properties and instantaneous aerosol forcing. The evaluation of the simulated aerosol absorption optical depth with the AERONET sun-photometer network shows a good agreement in the large scale global patterns. On a regional basis it becomes evident that the update of the BC refractive indices to Bond and Bergstrom (2006) significantly improves the previous underestimation of the aerosol absorption optical depth. In the global annual-mean, absorption acts to reduce the shortwave anthropogenic aerosol top-of-atmosphere (TOA) radiative forcing clear-sky from -0.79 to -0.53 W m(sup -2) (33%) and all-sky from -0.47 to -0.13W m(sup -2 (72%). Our results confirm that basic assumptions about the BC refractive index play a key role for aerosol absorption and radiative forcing. The effect of the usage of more accurate effective medium approximations is comparably small. We demonstrate that the diversity in the AeroCom land-surface albedo fields contributes to the uncertainty in the simulated anthropogenic aerosol radiative forcings: the usage of an upper versus lower bound of the AeroCom land albedos introduces a global annual-mean TOA forcing range of 0.19W m(sup -2) (36%) clear-sky and of 0.12W m(sup -2) (92%) all-sky. The consideration of black carbon inclusions on cloud radiative properties results in a small global annual-mean all-sky absorption of 0.05W m(sup -2) and a positive TOA forcing perturbation of 0.02W m(sup -2). The long-wave aerosol radiative effects are small for anthropogenic aerosols but become of relevance for the larger natural dust and sea-salt aerosols.

Stier, Philip↗