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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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Detector monitors gamma dose rate at particular position in a radiation facility where a mixed neutron-gamma environment exists, thus determining reactor power level changes. Device also maps gamma intensity profile across a neutron-gamma beam.
New observations at submillimeter wavelengths of the Orion Nebula and NGC 2024 are shown to provide a rather detailed map of the Orion Nebula at these wavelengths. The Orion Nebula emission is attributed to optically thin thermal radiation from dust grains in the molecular cloud with peak emission centered in the Kleinmann-Low nebula source.
The southern H II region G333.6-0.2, which has a total luminosity of 3.3 million solar luminosities (for an assumed distance of 4 kpc) was mapped at 2.2, 10, 30, 50, and 100 microns. At all wavelengths, the surface brightness of the infrared radiation is unusually high and the structure of the source is compact and symmetrical. The present observations, along with previous data, suggest that G333.6-0.2 is excited by a single luminous object or a very compact cluster, which has formed on the front surface of a dense molecular cloud as seen from the earth. It is shown that the spectral and spatial characteristics of the infrared radiation can be understood in terms of this blister model.
A procedure is developed for calculating atmospheric extinction characteristics (optical thickness, scattering height, single scattering albedo) and surface albedo from radiometric images made at satellite altitudes. The procedure - a fast, computerized method - is suitable for the high-volume processing of satellite imagery data and thus can be used to map temporal and spatial distributions of aerosol parameters. Based on an analytical approximate solution to the equation of radiative transfer in a plane parallel atmosphere, the procedure is primarily applicable to the 0.4-micron to 0.8-micron wavelength range for solar zenith angles from 10 deg to 60 deg, surface albedos between 0.03 and about 0.5, and atmospheric optical thicknesses from 0.2 to 2. With a step-like change in the surface albedo (for example, a seashore or river bank or other similar change of terrain), both surface reflectivity and atmospheric optical thickness can be derived from radiance measurements. In this case, the resultant optical thickness is not based on a known surface reflectivity and is in essence independent of the radiometer calibration.
Imaging spectrometer for use in crop and mineral resource-mapping experiments is scaled-down version. Compact imaging spectrometer uses Schmidt/Littrow optics with single spherical primary mirror. Radiation from scene strikes reflecting Schmidt corrector plate located near center of curvature of primary spherical mirror.
The Solar Backscatter Ultraviolet and Total Ozone Mapping Spectrometer (SBUV/TOMS) onboard the Nimbus 7 satellite is an atmospheric ozone measuring experiment from solar backscattered ultraviolet radiation off the earth atmosphere. The excellent spatial coverage and long lifetime of SUBV/TOMS makes this experiment viable for the long term monitoring of the global ozone. A technique used in the in-orbit calibration of SUBV/TOMS for the ozone data processing is presented. This technique employs a model to explain and correct the observed instrument output due to degradation. From the analyses with the corrected data to verify the model, it is concluded that the in-orbit instrument calibration for the ozone measurement is accurate within 2 percent for the first four years of the instrument operation.
In the past year we have been investigating a new algorithm for the derivation of column sulfur dioxide, column ozone, and aerosol optical depth from the Total Ozone Mapping Spectrometer (TOMS) High Density TOMS (HDT) archived albedos. Simulations of the measured albedos were made using a radiative transfer model, and a technique developed to separate the effects of the aerosol optical depth from the absorption optical depth. The retrieval adopted obtained values from the three parameters with high accuracy. This retrieval was then applied to the TOMS data.
The preliminary results obtained with the solar extreme ultraviolet spectrometer, onboard the Solar and Heliospheric Observatory (SOHO), are reported on. The solar ultraviolet measurement of emitted radiation (SUMER) instrument established a long time series of the network evolution in following the solar rotation. The maps of the network evolution were obtained in lines spanning from 10(sup 4) K to 6 x 10(sup 6) K. Line profiles were also recorded with a sampling of 1 x 0.76 sq arcsec over the entire field. The progress analysis of this set of data is underlined and the velocity distribution in the cell network is considered.
In this paper we derive the average configuration of the ring current as a function of the state of the magnetosphere as indicated by the Dst index. We sort magnetic field data from the Combined Release and Radiation Effects Satellite (CRRES) by spatial location and by the Dst index in order to produce magnetic field maps. From these maps we calculate local current systems by taking the curl of the magnetic field. NN7e find both the westward (outer) and the eastward (inner) components of the ring current. We find that the ring current intensity varies linearly with D.St as expected, and that the ring current is asymmetric for all Dst values. The azimuthal peak of the ring current is located in the afternoon sector for quiet conditions, and near midnight for disturbed conditions. The ring current also moves closer to the Earth during disturbed conditions. We are able to recreate the Dst index by integrating the magnetic perturbations caused by the ring current. We find that we needed to apply a 20 nT offset to Dst, and assume a perfectly conducting Earth to obtain an optimal agreement between the computed and the observed Dst. We interpret the 20 nT offset as the magnetic field generated by the quiet time ring current used as baseline in computing Dst.
The combustion and extinction behavior of a diffusion flame around a solid fuel cylinder (PMMA) in low-speed forced flow in zero gravity was studied numerically using a quasi-steady gas phase model. This model includes two-dimensional continuity, full Navier Stokes' momentum, energy, and species equations with a one-step overall chemical reaction and second-order finite-rate Arrhenius kinetics. Surface radiation and Arrhenius pyrolysis kinetics are included on the solid fuel surface description and a parameter Phi, representing the percentage of gas-phase conductive heat flux going into the solid, is introduced into the interfacial energy balance boundary condition to complete the description for the quasi-steady gas-phase system. The model was solved numerically using a body-fitted coordinate transformation and the SIMPLE algorithm. The effects of varying freestream velocity and Phi were studied. These parameters have a significant effect on the flame structure and extinction limits. Two flame modes were identified: envelope flame and wake flame. Two kinds of flammability limits were found: quenching at low-flow speeds due to radiative loss and blow-off at high flow speeds due to insufficient gas residence time. A flammability map was constructed showing the existence of maximum Phi above which the solid is not flammable at any freestream velocity.
Global distribution of aeolian dust is simulated from 1981 to 1996 with the Goddard Ozone Chemistry Aerosol Radiation and Transport (GOCART) model. The results are assessed with in-situ measurements and the Total Ozone Mapping Spectrometer (TOMS) aerosol products. The annual budget over the different continents and oceans are analyzed. It is found that there is a maximum of 25% difference of global annual emission from the minimum in 1996 to the maximum in 1988. There is a downward trend of dust emission over Africa and East Asia, of 6 and 2 Tg/yr, respectively. The inter-annual variability of dust distribution is analyzed over the North Atlantic and Africa. It is found that in winter most of the North Atlantic and Africa dust loading is correlated with the North Atlantic Oscillation. The GOCART model indicates that a controlling factor of such correlation can be attributed to dust emission from the Sahel. The Bodele depression is the major dust source in winter and its inter-annual variability is highly correlated with the NAO. However, it is not possible to conclude without further analysis that the North Atlantic Oscillation is forcing the inter-annual variability of dust emission and in-turn dust concentration over the North Atlantic.
The National Aeronautics and Space Administration (NASA) Wallops Flight Facility (WFF) P-3B Orion is a medium-lift, four engine turbo-prop aircraft that has been reconfigured from a military aircraft to an Earth Science research platform. The aircraft has a long history of supporting science missions, flying on average over 200 hours per year. Examples of research missions that have been flown aboard the aircraft are remote sensing flights to study geophysical parameters including ice-sheet topography and periodic change, soil moisture content, atmospheric aerosol constituents, and beach erosion. Missions are conducted for the purposes of calibration/validation of various NASA and international satellites that monitor climate change as well as process studies and the test of new prototype remote sensing instruments. In recent y ears the focus has been on ice surveys of the Arctic and Antarctic, soil moisture research, and measurements of atmospheric chemistry and radiation sciences. The aircraft has been conducting ice surveys of Greenland since 1993 for the purposes of topographic mapping of both the surface and basal topography. Another application of the aircraft has been for soil moisture research. Research has also been conducted using microwave radiometers and radars over various agricultural and forest lands. Recently, a mission was flown in the spring over the High-Arctic to collect air samples of haze and boreal forest fires in an effort to determine anthropogenic amounts and sources of pollution. This pa per will provide an overview of the P-3B platform and highlight recent science missions.
This article combined several infrared datasets to study the vertical properties of Saturn's northern springtime storm. Spectroscopic observations of Saturn's northern hemisphere at 0.5 and 2.5 / cm spectral resolution were provided by the Cassini Composite Infrared Spectrometer (CIRS, 17). These were supplemented with narrow-band filtered imaging from the ESO Very Large Telescope VISIR instrument (16) to provide a global spatial context for the Cassini spectroscopy. Finally, nightside imaging from the Cassini Visual and Infrared Mapping Spectrometer (VIMS, 22) provided a glimpse of the undulating cloud activity in the eastern branch of the disturbance. Each of these datasets, and the methods used to reduce and analyse them, will be described in detail below. Spatial maps of atmospheric temperatures, aerosol opacity and gaseous distributions are derived from infrared spectroscopy using a suite of radiative transfer and optimal estimation retrieval tools developed at the University of Oxford, known collectively as Nemesis (23). Synthetic spectra created from a reference atmospheric model for Saturn and appropriate sources of spectroscopic line data (6, 24) are convolved with the instrument function for each dataset. Atmospheric properties are then iteratively adjusted until the measurements are accurately reproduced with physically-realistic temperatures, compositions and cloud opacities.
The Origins Spectral Interpretation Resource Identification Security Regolith Explorer (OSIRIS-REx) mission is a NASA New Frontiers mission launching in 2016 to rendezvous with the small, Earth-crossing asteroid (101955) Bennu in late 2018, and ultimately return a sample of regolith to Earth. Approximately 3 months before the encounter with Bennu, the asteroid finally becomes detectable in the narrow field PolyCam imager. The spacecraft's rendezvous with Bennu begins with a series of four Asteroid Approach Maneuvers, which slow the spacecraft's speed relative to Bennu beginning two and a half months prior to closest approach, ultimately delivering the spacecraft to a point 18 km from Bennu on Nov 18, 2018. An extensive campaign of proximity operations activities to characterize the properties of Bennu and select a suitable sample site will follow. This paper will discuss the challenges of navigating near a small 500-m diameter asteroid. The navigation at close proximity is dependent on the accurate mathematical model or digital terrain map of the asteroids shape. Predictions of the spacecraft state are very sensitive to spacecraft small forces, solar radiation pressure, and mis-modeling of Bennu's gravity field. Uncertainties in the physical parameters of the central body Bennu create additional challenges. The navigation errors are discussed and their impact on science planning will be presented.
A new multilayer IST-albedo Moderate Resolution Imaging Spectroradiometer (MODIS) product of Greenland was developed to meet the needs of the ice sheet modeling community. The multiple layers of the product enable the relationship between IST and albedo to be evaluated easily. Surface temperature is a fundamental input for dynamical ice sheet models because it is a component of the ice sheet radiation budget and mass balance. Albedo influences absorption of incoming solar radiation. The daily product will combine the existing standard MODIS Collection-6 ice-surface temperature, derived melt maps, snow albedo and water vapor products. The new product is available in a polar stereographic projection in NetCDF format. The product will ultimately extend from March 2000 through the end of 2017.
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The morphology, kinematics, and ionization state of the nuclear extended narrow-line region (ENLR) of the Seyfert 2 galaxy Mrk 573 are studied using narrow-band images of a grid of long-slit spectra. The entire ENLR is mapped spectroscopically, and velocity structure is studied. The velocity field map shows a typical galactic rotation picture with some important deviations. A simple geometric model, in accordance with the 'unified schemes', is employed to study the effects of various parameters of the observed picture. The best match is achieved when a biconical radiation field illuminates the ISM of the host galaxy that takes part in a normal galaxy rotation but also has radial motions close to the nucleus. The emission-line images reveal an ENLR elongated along the radio axis in the northwest-southeast direction, but a map of the flux ratio forbidden O III 5007/(H-alpha + forbidden N II) shows a different structure, with the highest excitation peak offset by about 4 arcsec along the radio axis to the southeast.
A simple algorithm and computer program were developed for determining the actual surface temperature from the effective brightness temperature as measured remotely by a radiation thermometer called PRT-5. This procedure allows the computation of atmospheric correction to the effective brightness temperature without performing detailed radiative transfer calculations. Model radiative transfer calculations were performed to compute atmospheric corrections for several values of the surface and atmospheric parameters individually and in combination. Polynomial regressions were performed between the magnitudes or deviations of these parameters and the corresponding computed corrections to establish simple analytical relations between them. Analytical relations were also developed to represent combined correction for simultaneous variation of parameters in terms of their individual corrections.