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All sourcesNASA NTRSDOE OSTI
NASA NTRS2003

The Study of Biomass Emissions for Defining Radiative Forcing of Climate

Accurate quantification of the amounts of trace gases and particulate matter emitted from vegetation fires and other sources of biomass burning (agricultural waste and biofuels) on a regional and global basis is required by a number of users, including scientists studying a wide range of atmospheric processes, national governments who are required to report greenhouse gas emissions, and those interested in quantifying the sources of air pollution that affect human health at regional scales. Over the past decade, improvements in the ability to detect and map fires using a number of different satellite systems have been achieved, largely through efforts coordinated through working groups organized by the IGBP Data and Information System and Global Observation of Forest Cover (GOFC) projects. In addition, significant advances and improvement in or understanding of the emissions factors for biomass burning in different biomes has resulted through efforts by the Biomass Burning Experiment (BIBEX) organized through the International Global Atmospheric Chemistry project. A number of satellite-based fire data products have been generated, and a number of new products will shortly be available. These new data products will provide the basis for estimating emissions from biomass burning on a global basis. However, a number of issues remain concerning the availability of other data sets needed to generate these estimates. Recognizing these issues, the GOFC-Fire Satellite Validation Workshop (held in Lisbon, Portugal on 9-11 July 2001), recommended that a workshop focusing on Improving Global Estimates of Atmospheric Emissions from Biomass Burning be organized. This workshop was held from 17- 19 July 2002 on the campus of the University of Maryland, College Park, Maryland. This workshop served as the annual meeting of the GOFC/GOLD-Fire Program. The overall goals of the meeting were to review the information products generated from satellite imagery and other sources that are currently available for developing emission estimates from biomass burning, evaluate areas where improved or additional products would be beneficial, and recommend products for use by the atmospheric science community.

Penner, Joyce↗
NASA NTRS2022

The H2o Content of the Ureilite Parent Body

The fate of highly volatile elements (H, C, F, Cl and S) during planetary accretion and differentiation is debated. Recent analyses of water in non-carbonaceous chondrites (RC, OC, EC) and achondrites (angrites, eucrites) have been used to argue that inner solar system parent bodies accreted and retained their highly volatile element budgets from their primary feedstock without substantial loss during accretion, metamorphism and differentiation. An alternative model posits that differentiated inner solar system parent bodies (e.g., the angrite parent body, 4 Vesta, Earth) derived the majority of their water from a carbonaceous chondrite-like source, delivered during the final stages of accretion. In order to add new constraints to this debate, we have measured water in nominally anhydrous minerals, melt inclusions, and interstitial glass in ureilites, the largest group of primitive achondrites in the terrestrial meteorite collection. Primitive achondrites did not experience global melting and homogenization. Therefore, these meteorites capture part of the transition from chondritic to achondritic parent bodies, allowing us to constrain the fate of water during the earliest stages of differentiation. Our nano-scale secondary ion mass spectrometry (nanoSIMS) analyses allow us to assess the viability of ureilite-like material as a potential source of terrestrial water. Analyses of pigeonite in main group ureilites yield a range of 2.0 – 6.0 µg/g H2O, and analyses of high-Ca pyroxene and glass (glassy melt inclusions and interstitial glass) in the Almahata Sitta ureilitic trachyandesite yield ranges of 13 – 19 µg/g H2O and 44 – 216 µg/g H2O, respectively. Mass balance, incremental melting, and batch melting calculations yield a preferred ureilite parent body H2O content of 2 – 20 µg/g, similar to previous estimates of water in the eucrite parent body (4 Vesta), but lower than estimates of Earth’s water budget. With these data, we demonstrate that 1) the ureilite parent body is H2O-depleted relative to the Earth; 2) ureilite-like material is unlikely to be a primary source of H2O to the Earth; 3) C and H are not necessarily coupled elements during planetary accretion and thermal processing; and 4) accretion, heating, partial melting, and degassing of rocky planetesimals likely results in significant depletion of H2O.

Primitive achondrites↗
NASA NTRS1984

The nature of the embedded population in the Rho Ophiuchi dark cloud - Mid-infrared observations

In combination with previous IR and optical data, the present 10-20 micron observations of previously identified members of the embedded population of the Rho Ophiuchi dark cloud allow determinations to be made of the broadband energy distributions for 32 of the 44 sources. The majority of the sources are found to emit the bulk of their luminosity in the 1-20 micron range, and to be surrounded by dust shells. Because they are, in light of these characteristics, probably premain-sequence in nature, relatively accurate bolometric luminosities for these objects can be obtained through integration of their energy distributions. It is found that 44 percent of the sources are less luminous than the sun, and are among the lowest luminosity premain-sequence/protostellar objects observed to date.

Lada, C. J.↗
NASA NTRS1987

Discrete X-ray sources and the X-ray background

Since the discovery of a highly uniform X-ray background (XRB) in the 2 to 10 keV range, its nature is not yet fully explained. It appears clear from the results of Einstein medium and deep surveys that at least 50% of the XRB is due to individual extragalactic sources when their contribution is integrated to Z = 3. This includes contribution from Quasi Stellar Objects (QSOs), Active Galactic Nuclei (AGNs), galaxies, and clusters of galaxies. The average spectrum of each of the individual contributing sources is softer than that of the observed XRB. Therefore, the remaining contribution must have a rather hard spectrum of alpha nearly equal to 0.0 to 0.2. It is unlikely that this spectrum can be produced by diffuse processes. Therefore, the remainder of the XRB must be due to individual sources with the appropriate spectrum. This requires either that the spectrum of the already identified sources changes at early epochs or a new class of objects. Advanced X-ray Astrophysics Facility (AXAF) observations will extend survey sensitivity to limiting fluxes of order of 3 x 10 to the minus 16 erg/sq cm/s, some 50 times fainter than any previous survey. There will be sufficient sensitivity and angular resolution to permit identification and study of these objects.

Giacconi, Riccardo↗
NASA NTRS1992

The structure of horizontal-branch models. I - The zero-age horizontal branch

A detailed study of the structure of zero-age horizontal-branch (ZAHB) models is studied in order to show how the hydrostatic structure of these models changes with the input parameters and determines the H-R diagram location of a given model. The properties of composite polytropes on the homology-invariant (U,V)-plane are demonstrated. A variety of test models and sequences were constructed to elucidate the underlying factors that give rise to the wide variation in HB model properties with composition. The roles of the CNO elements as nuclear catalysts and of the envelope sources, as well as the envelope helium abundance are reexamined. It is found that, for stars of a fixed range of mass arriving on the HB, the stellar distribution is determined mainly by CNO for low metallicities (Fe/H of less than about -1), but mainly by opacity sources for high metallicities. The value of Fe/H where CNO ceases to dominate depends significantly on the adopted opacity and will decrease if and when opacity estimates are revised upward.

Dorman, Ben↗
NASA NTRS2022

The Zn, S, and Cl Isotope Compositions of Mare Basalts: Implications for the Effects of Eruption Style and Pressure on Volatile Element Stable Isotope Fractionation on the Moon

We compare the stable isotope compositions of Zn, S, and Cl for Apollo mare basalts to better constrain the sources and timescales of lunar volatile loss. Mare basalts have broadly elevated yet limited ranges in δ(66)Zn, δ(34)S, and δ(37)Cl_(SBC+WSC) values of 1.27 ± 0.71, 0.55 ± 0.18, and 4.1 ± 4.0‰, respectively, compared to the silicate Earth at 0.15, –1.28, and 0‰, respectively. We find that the Zn, S, and Cl isotope compositions are similar between the low- and high-Ti mare basalts, providing evidence of a geochemical signature in the mare basalt source region that is inherited from lunar formation and magma ocean crystallization. The uniformity of these compositions implies mixing following mantle overturn, as well as minimal changes associated with subsequent mare magmatism. Degassing of mare magmas and lavas did not contribute to the large variations in Zn, S, and Cl isotope compositions found in some lunar materials (i.e., 15‰ in δ(66)Zn, 60‰ in δ(34)S, and 30‰ in δ(37)Cl). This reflects magma sources that experienced minimal volatile loss due to high confining pressures that generally exceeded their equilibrium saturation pressures. Alternatively, these data indicate effective isotopic fractionation factors were near unity. Our observations of S isotope compositions in mare basalts contrast to those for picritic glasses (Saal and Hauri 2021), which vary widely in S isotope compositions from –14.0 to 1.3‰, explained by extensive degassing of picritic magmas under high-P/P_(Sat) values (>0.9) during pyroclastic eruptions. The difference in the isotope compositions of picritic glass beads and mare basalts may result from differences in effusive (mare) and explosive (picritic) eruption styles, wherein the high-gas contents necessary for magma fragmentation would result in large effective isotopic fractionation factors during degassing of picritic magmas. Additionally, in highly vesiculated basalts, the δ(34)S and δ(37)Cl values of apatite grains are higher and more variable than the corresponding bulk-rock values. The large isotopic range in the vesiculated samples is explained by late-stage low-pressure “vacuum” degassing (P/P-(Sat) ~ 0) of mare lavas wherein vesicle formation and apatite crystallization took place post-eruption. Bulk-rock mare basalts were seemingly unaffected by vacuum degassing. Degassing of mare lavas only became important in the final stages of crystallization recorded in apatite—potentially facilitated by cracks/fractures in the crystallizing flow. We conclude that samples with wide-ranging volatile element isotope compositions are likely explained by localized processes, which do not represent the bulk Moon.

Halogens↗
NASA NTRS1987

Crew activity and motion effects on the space station

Among the significant sources of internal disturbances that must be considered in the design of space station vibration control systems are the loads induced on the structure from various crew activities. Flight experiment T013, flown on the second manned mission of Skylab, measured force and moment time histories for a range of preplanned crew motions and activities. This experiment has proved itself invaluable as a source of on-orbit crew induced loads that has allowed a space station forcing function data base to be built. This will enable forced response such as acceleration and deflections, attributable to crew activity, to be calculated. The flight experiment, resultant database and structural model pre-processor, analysis examples and areas of combined research shall be described.

Rochon, Brian V.↗
NASA NTRS1996

Predicted Turbine Heat Transfer for a Range of Test Conditions

Comparisons are shown between predictions and experimental data for blade and endwall heat transfer. The comparisons of computational domain parisons are given for both vane and rotor geometries over an extensive range of Reynolds and Mach numbers. Comparisons are made with experimental data from a variety of sources. A number of turbulence models are available for predicting blade surface heat transfer, as well as aerodynamic performance. The results of an investigation to determine the turbulence model which gives the best agreement with experimental data over a wide range of test conditions are presented.

Boyle, R. J.↗
NASA NTRSDate not supplied

Landslide Runout Analysis Using Remote Sensing for Lower and Upper Barun Lakes

Landslides are recognized as common triggers of glacial lake outburst floods in high mountain regions, but the remoteness of dangerous glacial lakes makes monitoring and disaster management very difficult. Using a very high resolution digital elevation model produced from a series of stereo satellite images, we simulate debris flows and rock avalanche runout around two very dangerous lakes in high mountain Nepal. We constrain particularly likely sources of these slope failures to simulate 79,800 potential debris flows and rock avalanches of volumes ranging from 1,000 m3 to 1,000,000 m3. This allowed us to identify zones in and around dangerous glacial lakes that are most exposed to landslide runout hazards, along with the most frequent source areas that produced landslides that may run into either of the two glacial lakes. Although our empirical-statistical model presented limitations that numerical models attempt to overcome, our probabilistic approach combined with a very high resolution DEM may shed new light on how to identify sources and impact areas of debris flows and rock avalanches that may cascade into downstream disasters.

landslides↗
NASA NTRS2009

GEMS

The prime scientific objectives of the Gravity and Extreme Magnetism SMEX, GEMS, are to determine the effects of the spin of black holes, the configurations of the magnetic fields of magnetars, and the structure of the supernova shocks which accelerate cosmic rays. In the cases of both stellar black holes and supermassive black holes, sensitivity to 1% polarization is needed to make diagnostic measurements of the net polarizations predicted for probable disk and corona models. GEMS can reach this goal for several Seyferts and quasars and measure the polarizations of representatives of a variety of other classes of X-ray sources, such as rotation-powered and accretion-powered pulsars. GEMS uses foil mirrors to maximize the collecting area achievable within the SMEX constraints. The polarimeters at the mirror foci are Time Projection Chambers which use the photoelectic effect to measure the polarization of the incident photon. We have built laboratory models with good efficiency and modulation in the 2-10 keV range. An attached small student experiment would add 0.5 keV sensitivity for bright soft sources. The instrument has a point spread function which allows measurement of structures in the brighter nearby supernova remnants. GEMS' Orbital Sciences spacecraft will rotate at a rate of 0.1 revolutions per minute during observations, so that systematic errors due to the detector can be detected and corrected. A program of 35 sources can be observed in 9 months. GEMS is designed for a two year lifetime which will allow a General Observer program that would more than double the number of sources measured. For subsets of black holes, neutron stars and supernova remnants, GEMS will measure the polarization of several sources, solving important questions while establishing the sensitivity required for future missions.

Swank, Jean↗
NASA NTRS2004

Miniature Radioisotope Thermoelectric Power Cubes

Cube-shaped thermoelectric devices energized by a particles from radioactive decay of Cm-244 have been proposed as long-lived sources of power. These power cubes are intended especially for incorporation into electronic circuits that must operate in dark, extremely cold locations (e.g., polar locations or deep underwater on Earth, or in deep interplanetary space). Unlike conventional radioisotope thermoelectric generators used heretofore as central power sources in some spacecraft, the proposed power cubes would be small enough (volumes would range between 0.1 and 0.2 cm3) to play the roles of batteries that are parts of, and dedicated to, individual electronic-circuit packages. Unlike electrochemical batteries, these power cubes would perform well at low temperatures. They would also last much longer: given that the half-life of Cm-244 is 18 years, a power cube could remain adequate as a power source for years, depending on the power demand in its particular application.

Patel, Jagdish U.↗
NASA NTRS2001

Preliminary Design of a Lightning Optical Camera and ThundEr (LOCATE) Sensor

The preliminary design of an optical/acoustical instrument is described for making highly accurate real-time determinations of the location of cloud-to-ground (CG) lightning. The instrument, named the Lightning Optical Camera And ThundEr (LOCATE) sensor, will also image the clear and cloud-obscured lightning channel produced from CGs and cloud flashes, and will record the transient optical waveforms produced from these discharges. The LOCATE sensor will consist of a full (360 degrees) field-of-view optical camera for obtaining CG channel image and azimuth, a sensitive thunder microphone for obtaining CG range, and a fast photodiode system for time-resolving the lightning optical waveform. The optical waveform data will be used to discriminate CGs from cloud flashes. Together, the optical azimuth and thunder range is used to locate CGs and it is anticipated that a network of LOCATE sensors would determine CG source location to well within 100 meters. All of this would be accomplished for a relatively inexpensive cost compared to present RF lightning location technologies, but of course the range detection is limited and will be quantified in the future. The LOCATE sensor technology would have practical applications for electric power utility companies, government (e.g. NASA Kennedy Space Center lightning safety and warning), golf resort lightning safety, telecommunications, and other industries.

Phanord, Dieudonne D.↗
NASA NTRS2007

All Source Solution Decision Support Products Created for Stennis Space Center in Response to Hurricane Katrina

In the aftermath of Hurricane Katrina and in response to the needs of SSC (Stennis Space Center), NASA required the generation of decision support products with a broad range of geospatial inputs. Applying a systems engineering approach, the NASA ARTPO (Applied Research and Technology Project Office) at SSC evaluated the Center's requirements and source data quality. ARTPO identified data and information products that had the potential to meet decision-making requirements; included were remotely sensed data ranging from high-spatial-resolution aerial images through high-temporal-resolution MODIS (Moderate Resolution Imaging Spectroradiometer) products. Geospatial products, such as FEMA's (Federal Emergency Management Agency's) Advisory Base Flood Elevations, were also relevant. Where possible, ARTPO applied SSC calibration/validation expertise to both clarify the quality of various data source options and to validate that the inputs that were finally chosen met SSC requirements. ARTPO integrated various information sources into multiple decision support products, including two maps: Hurricane Katrina Inundation Effects at Stennis Space Center (highlighting surge risk posture) and Vegetation Change In and Around Stennis Space Center: Katrina and Beyond (highlighting fire risk posture).

Ross, Kenton W.↗
NASA NTRS2010

High-resolution three-dimensional imaging radar

A three-dimensional imaging radar operating at high frequency e.g., 670 GHz, is disclosed. The active target illumination inherent in radar solves the problem of low signal power and narrow-band detection by using submillimeter heterodyne mixer receivers. A submillimeter imaging radar may use low phase-noise synthesizers and a fast chirper to generate a frequency-modulated continuous-wave (FMCW) waveform. Three-dimensional images are generated through range information derived for each pixel scanned over a target. A peak finding algorithm may be used in processing for each pixel to differentiate material layers of the target. Improved focusing is achieved through a compensation signal sampled from a point source calibration target and applied to received signals from active targets prior to FFT-based range compression to extract and display high-resolution target images. Such an imaging radar has particular application in detecting concealed weapons or contraband.

Cooper, Ken B.↗
NASA NTRS2009

Lunar Neutral Exposphere Properties from Pickup Ion Analysis

Composition and structure of neutral constituents in the lunar exosphere can be determined through measurements of phase space distributions of pickup ions borne from the exosphere [1]. An essential point made in an early study [ 1 ] and inferred by recent pickup ion measurements [2, 3] is that much lower neutral exosphere densities can be derived from ion mass spectrometer measurements of pickup ions than can be determined by conventional neutral mass spectrometers or remote sensing instruments. One approach for deriving properties of neutral exospheric source gasses is to first compare observed ion spectra with pickup ion model phase space distributions. Neutral exosphere properties are then inferred by adjusting exosphere model parameters to obtain the best fit between the resulting model pickup ion distributions and the observed ion spectra. Adopting this path, we obtain ion distributions from a new general pickup ion model, an extension of a simpler analytic description obtained from the Vlasov equation with an ion source [4]. In turn, the ion source is formed from a three-dimensional exospheric density distribution, which can range from the classical Chamberlain type distribution to one with variable exobase temperatures and nonthermal constituents as well as those empirically derived. The initial stage of this approach uses the Moon's known neutral He and Na exospheres to deriv e He+ and Na+ pickup ion exospheres, including their phase space distributions, densities and fluxes. The neutral exospheres used are those based on existing models and remote sensing studies. As mentioned, future ion measurements can be used to constrain the pickup ion model and subsequently improve the neutral exosphere descriptions. The pickup ion model is also used to estimate the exosphere sources of recently observed pickup ions on KAGUYA [3]. Future missions carrying ion spectrometers (e.g., ARTEMIS) will be able to study the lunar neutral exosphere with great sensitivity, yielding the necessary ion velocity spectra needed to further analysis of parent neutral exosphere properties.

Hartle, R. E.↗
NASA NTRS1984

Stray light analysis of the Diffuse Infrared Background Experiment (DIRBE)

The straylight analysis of the diffuse infrared background experiment (DIRBE) on the cosmic background explorer (COBE) mission is discussed. From the statement of work (SOW), the purpose of DIRBE is to measure, or set upper limits on, the spectral and spatial character of the diffuse extra galactic infrared radiation. Diffuse infrared sources within our own galaxy are measured. The required reduction of the unwanted radiation imposes severe design and operating restrictions on the DIRBE instrument. To accomplish its missions, it will operate at a multitude of wavelengths ranging from 1.25 um out to 200 to 300 microns. The operating bands and the required point source normalized irradiance transmittance (PSNIT) are shown. The important straylight concepts in the DIRBE design are reviewed. The model and assumptions used in APART analysis are explained. The limitations due to the scalar theory used in the analysis are outlined.

Breault, R. P.↗
NASA NTRS2016

The Sample at Mars Analysis (SAM) Detections of CO2 and CO in Sedimentary Material from Gale Crater, Mars: Implications for the Presence of Organic Carbon and Microbial Habitability on Mars

Sedimentary rock samples heated to 860 C in the SAM instrument evolved CO2 and CO indicating the presence of organic-carbon(C) in Gale Crater materials. Martian or exogenous (meteoritic, interplanetary dust) CO2 and CO could be derived from combustion of simple organics (less than 300 C), complex refractory organics/amorphous carbon (300-600 C), and/or magmatic carbon (greater than 600 C) as result of thermal decomposition of Gale Crater perchlorates, and sulfates present that produce O2. Oxidized organic compounds could also evolve CO2 and CO over broad temperature range (150 to 800 C) and such organics are expected on Mars via exogenous sources. Alternatively, organic-C could also have been oxidized to carboxylic acids [e.g, mellitic acid (RCOOH), acetate (CH3CO2(-)), and oxalates ((2)C2O4(-))] by oxidative radiolytic weathering, or other oxidation processes. The presence of oxidized organics is consistent with the limited detection of reduced organic-C phases by the SAM-gas chromatography. Organic-C content as determined by CO2 and CO contents could range between 800 and 2400 ppm C indicating that substantial organic-C component is present in Gale Crater. There are contributions from SAM background however, even in worse case scenarios, this would only account for as much as half of the detected CO2 and CO. Nevertheless, if organic-C levels were assumed to have existed in a reduced form on ancient Mars and this was bioavailable C, then less than 1% of C in Gale Crater sediments could have supported an exclusively heterotrophic microbial population of 1 x 10(exp 5) cells/g sediment (assumes 9 x 10(exp -7) microgram/cell and 0.5 micrograms C/microgram cell). While other essential nutrients (e.g., S and P) could be limiting, organic-C contents, may have been sufficient to support limited heterotrophic microbial populations on ancient Mars.

Sutter, Brad↗
NASA NTRS1992

Compton backscattered annihilation line emission: A new diagnostic of accreting compact sources

It is shown that Compton scattering of 511 keV electron-positron annihilation radiation produces a line like feature at approx. 170 keV from backscattered photons. Assuming a simple model of an accretion disk around a compact source, the spectrum is explored of the spectrum of Compton scattered annihilation line emission for a range of conditions. It is further shown that such Compton baskscattering of annihilation line emission from the inner edge of an accretion disk could account for the previously unidentified 170 keV line emission and high energy continuum observed from a variable, compact source, or sources, of annihilation radiation near the Galactic Center. Identification of the observed 170 keV line as an annihilation line reflection feature provides strong new evidence that the source of the emission is an accreting compact object. Further study of these features in existing spectra and in forthcoming GRO observation of these and other sources can provide unique new diagnostics of the innermost regions of accretion disks around compact objects.

Lingenfelter, Richard E.↗