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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 613 records · Page 34
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Far Infrared Observations of Molecular Clouds in the Outer Galaxy

The existence of molecular clouds in the outer galaxy allows the study of star formation at large galactocentric radii. The study of these clouds has two aims. A systematic survey is underway to study the large scale distribution of the molecular clouds outside the solar circle. To understand the physical conditions in the clouds, fully sampled maps were (and are being) made in CO and other molecules. The continuum emission is also being mapped. The main objective in doing an infrared study was to obtain information on the luminosity of the stars formed in these clouds. Assuming all energy radiated from the star is absorbed by the dust and then re-radiated in the infrared, one can get an estimate of the star's luminosity by integrating the flux over the source and converting it to a luminosity. Until these observations, the only way of judging stellar luminosities was from peak CO temperatures. Accounting for beam dilution, Kutner and Mead inferred from these that the heat sources were late B or later stars. The Kupier Airborne Observatory was used to search 9 sources in 5 clouds for far infrared emission.

Mead, K. N.↗
NASA NTRS1988

Advancing-side directivity and retreating-side interactions of model rotor blade-vortex interaction noise

Acoustic data are presented from a 40 percent scale model of the four-bladed BO-105 helicopter main rotor, tested in a large aerodynamic wind tunnel. Rotor blade-vortex interaction (BVI) noise data in the low-speed flight range were acquired using a traversing in-flow microphone array. Acoustic results presented are used to assess the acoustic far field of BVI noise, to map the directivity and temporal characteristics of BVI impulsive noise, and to show the existence of retreating-side BVI signals. The characterics of the acoustic radiation patterns, which can often be strongly focused, are found to be very dependent on rotor operating condition. The acoustic signals exhibit multiple blade-vortex interactions per blade with broad impulsive content at lower speeds, while at higher speeds, they exhibit fewer interactions per blade, with much sharper, higher amplitude acoustic signals. Moderate-amplitude BVI acoustic signals measured under the aft retreating quadrant of the rotor are shown to originate from the retreating side of the rotor.

Martin, R. M.↗
NASA NTRS1991

Bow shock models of ultracompact H II regions

This paper presents models of ultracompact H II regions as the bow shocks formed by massive stars, with strong stellar winds, moving supersonically through molecular clouds. The morphologies, sizes and brightnesses of observed objects match the models well. Plausible models are provided for the ultracompact H II regions G12.21 - 0.1, G29.96 - 0.02, G34.26 + 0.15, and G43.89 - 0.78. To do this, the equilibrium shape of the wind-blown shell is calculated, assuming momentum conservation. Then the shell is illuminated with ionizing radiation from the central star, radiative transfer for free-free emission through the shell is performed, and the resulting object is visualized at various angles for comparison with radio continuum maps. The model unifies most of the observed morphologies of ultracompact H II regions, excluding only those objects with spherical shells. Ram pressure confinement greatly lengthens the life of ultracompact H II regions, explaining the large number that exist in the Galaxy despite their low apparent kinematic ages.

Mac Low, Mordecai-Mark↗
NASA NTRS1991

Extreme Ultraviolet Explorer. Long look at the next window

The Extreme Ultraviolet Explorer (EUVE) will map the entire sky to determine the existence, direction, brightness, and temperature of thousands of objects that are sources of so-called extreme ultraviolet (EUV) radiation. The EUV spectral region is located between the x-ray and ultraviolet regions of the electromagnetic spectrum. From the sky survey by EUVE, astronomers will determine the nature of sources of EUV light in our galaxy, and infer the distribution of interstellar gas for hundreds of light years around the solar system. It is from this gas and the accompanying dust in space that new stars and solar systems are born and to which evolving and dying stars return much of their material in an endless cosmic cycle of birth, death, and rebirth. Besides surveying the sky, astronomers will make detailed studies of selected objects with EUVE to determine their physical properties and chemical compositions. Also, they will learn about the conditions that prevail and the processes at work in stars, planets, and other sources of EUV radiation, maybe even quasars. The EUVE mission and instruments are described. The objects that EUVE will likely find are described.

Maran, Stephen P.↗
NASA NTRS1993

Three dimensional modeling of cirrus during the 1991 FIRE IFO 2: Detailed process study

A three-dimensional model of cirrus cloud formation and evolution, including microphysical, dynamical, and radiative processes, was used to simulate cirrus observed in the FIRE Phase 2 Cirrus field program (13 Nov. - 7 Dec. 1991). Sulfate aerosols, solution drops, ice crystals, and water vapor are all treated as interactive elements in the model. Ice crystal size distributions are fully resolved based on calculations of homogeneous freezing of solution drops, growth by water vapor deposition, evaporation, aggregation, and vertical transport. Visible and infrared radiative fluxes, and radiative heating rates are calculated using the two-stream algorithm described by Toon et al. Wind velocities, diffusion coefficients, and temperatures were taken from the MAPS analyses and the MM4 mesoscale model simulations. Within the model, moisture is transported and converted to liquid or vapor by the microphysical processes. The simulated cloud bulk and microphysical properties are shown in detail for the Nov. 26 and Dec. 5 case studies. Comparisons with lidar, radar, and in situ data are used to determine how well the simulations reproduced the observed cirrus. The roles played by various processes in the model are described in detail. The potential modes of nucleation are evaluated, and the importance of small-scale variations in temperature and humidity are discussed. The importance of competing ice crystal growth mechanisms (water vapor deposition and aggregation) are evaluated based on model simulations. Finally, the importance of ice crystal shape for crystal growth and vertical transport of ice are discussed.

Jensen, Eric J.↗
NASA NTRS2004

Lunar and Planetary Science XXXV: Venus

The session"Venus" included the following reports:Venera-Vega Geochemical Analyses: What Geologic Units are the Source of the Analyzed Material?; Mapping of Rift Zones on Venus, Preliminary Results: Spatial Distribution, Relationship with Regional Plains, Morphology of Fracturing, Topography and Style of Volcanism; An Effect of Stimulated Radiation Processes on Radio Emission from Major Planets; and Venusian Craters and the Origin of Coronae.

Source record↗
NASA NTRS2013

Airborne Particles: What We Have Learned About Their Role in Climate from Remote Sensing, and Prospects for Future Advances

Desert dust, wildfire smoke, volcanic ash, biogenic and urban pollution particles, all affect the regional-scale climate of Earth in places and at times; some have global-scale impacts on the column radiation balance, cloud properties, atmospheric stability structure, and circulation patterns. Remote sensing has played a central role in identifying the sources and transports of airborne particles, mapping their three-dimensional distribution and variability, quantifying their amount, and constraining aerosol air mass type. The measurements obtained from remote sensing have strengths and limitations, and their value for characterizing Earths environment is enhanced immensely when they are combined with direct, in situ observations, and used to constrain aerosol transport and climate models. A similar approach has been taken to study the role particles play in determining the climate of Mars, though based on far fewer observations. This presentation will focus what we have learned from remote sensing about the impacts aerosol have on Earths climate; a few points about how aerosols affect the climate of Mars will also be introduced, in the context of how we might assess aerosol-climate impacts more generally on other worlds.

aerosol-climate impacts↗
NASA NTRS1995

Remote sensing of smoke, clouds, and radiation using AVIRIS during SCAR experiments

During the past two years, researchers from several institutes joined together to take part in two SCAR experiments. The SCAR-A (Sulfates, Clouds And Radiation - Atlantic) took place in the mid-Atlantic region of the United States in July, 1993. remote sensing data were acquired with the Airborne Visible Infrared Imaging Spectrometer (AVIRIS), the MODIS Airborne Simulator (MAS), and a RC-10 mapping camera from an ER-2 aircraft at 20 km. In situ measurements of aerosol and cloud microphysical properties were made with a variety of instruments equipped on the University of Washington's C-131A research aircraft. Ground based measurements of aerosol optical depths and particle size distributions were made using a network of sunphotometers. The main purpose of SCAR-A experiment was to study the optical, physical and chemical properties of sulfate aerosols and their interaction with clouds and radiation. Sulfate particles are believed to affect the energy balance of the earth by directly reflecting solar radiation back to space and by increasing the cloud albedo. The SCAR-C (Smoke, Clouds And Radiation - California) took place on the west coast areas during September - October of 1994. Sets of aircraft and ground-based instruments, similar to those used during SCAR-A, were used during SCAR-C. Remote sensing of fires and smoke from AVIRIS and MAS imagers on the ER-2 aircraft was combined with a complete in situ characterization of the aerosol and trace gases from the C-131A aircraft of the University of Washington and the Cesna aircraft from the U.S. Forest Service. The comprehensive data base acquired during SCAR-A and SCAR-C will contribute to a better understanding of the role of clouds and aerosols in global change studies. The data will also be used to develop satellite remote sensing algorithms from MODIS on the Earth Observing System.

Gao, Bo-Cai↗
NASA NTRS1975

Thermal inertia mapping

A thermal model of the earth's surface has been developed and used to determine the thermal inertia of a test site in the Mojave Desert, California. The model, which includes meteorological heating terms as well as radiation and conduction heating terms, is used with remotely sensed surface temperature data to determine thermal inertia of materials. The thermal inertia is displayed in image form, and can aid in the differentiation of the various lithologic materials in the test site.

Kahle, A. B.↗
NASA NTRS1995

Initial vegetation species and senescience/stress indicator mapping in the San Luis Valley, Colorado using imaging spectrometer data

We analyzed AVIRIS data obtained over agricultural areas in the San Luis Valley of Colorado. The data were acquired on September 3, 1993. A combined method of radiative transfer modeling and ground calibration site reflectance was used to correct the flight data to surface reflectance. This method, called Radiative Transfer Ground Calibration, or RTGC, corrects for variable water vapor in the atmosphere and produces spectra free of artifacts with spectral channel to channel noise approaching the signal to noise of the raw data. The calibration site soil samples were obtained on the day of the overflight and measured on our laboratory spectrometer. The site was near the center of the AVIRIS scene and the spectra of the soil is spectrally bland, especially in the region of the chlorophyll absorption in the visible portion of the spectrum. The center of the scene is located at approximately 106 deg 03' longitude, 37 deg 23' latitude, and the scene covers about 92 square kilometers. This scene is one of 28 in the area for a general project to study the Summitville abandoned mine site, located in the mountains west of the San Luis Valley, and its effects on the surrounding environment.

Clark, Roger N.↗
NASA NTRS2013

Analysis of Saturn's Thermal Emission at 2.2-cm Wavelength: Spatial Distribution of Ammonia Vapor

This work focuses on determining the latitudinal structure of ammonia vapor in Saturn's cloud layer near 1.5 bars using the brightness temperature maps derived from the Cassini RADAR (Elachi et al., 2004) instrument, which works in a passive mode to measure thermal emission from Saturn at 2.2-cm wavelength. We perform an analysis of five brightness temperature maps that span epochs from 2005 to 2011, which are presented in a companion paper by Janssen et al. (2013a, this issue). The brightness temperature maps are representative of the spatial distribution of ammonia vapor, since ammonia gas is the only effective opacity source in Saturn's atmosphere at 2.2-cm wavelength. Relatively high brightness temperatures indicate relatively low ammonia relative humidity (RH), and vice versa. We compare the observed brightness temperatures to brightness temperatures computed using the Juno atmospheric microwave radiative transfer (JAMRT) program which includes both the means to calculate a tropospheric atmosphere model for Saturn and the means to carry out radiative transfer calculations at microwave frequencies. The reference atmosphere to which we compare has a 3x solar deep mixing ratio of ammonia (we use 1.352x10(exp -4) for the solar mixing ratio of ammonia vapor relative to H2; see Atreya, 2010) and is fully saturated above its cloud base. The maps are comprised of residual brightness temperatures-observed brightness temperature minus the model brightness temperature of the saturated atmosphere.

Atmospheres↗
NASA NTRS1992

Chemistry in circumstellar disks - CS toward HL Tauri

High spatial and spectral resolution dust continuum and CS line-emission maps of the material immediately surrounding HL Tauri are presented. The 3.06-thermal dust map gives an upper limit to the source size of roughly 200 AU. When combined with previous millimeter continuum measurements, a beta value of 1.2 +/-0.3 is derived along with a disk mass of 0.1 solar mass, in agreement with previous disk radiative transfer models of the IR and submillimeter flux from HL Tau. The low dust emissivity index as compared to particles in the diffuse ISM is best explained by grain growth or composition evolution. The present observations of the CS and CO emission lines forming the molecular cloud surrounding HL Tauri are consistent with the 'canonical' temperatures, densities, and abundances derived in other Taurus cloud cores. In contrast, the CS emission in aperture synthesis maps at 650-AU spatial resolution is most consistent with CS/CO ratios at least 25-50 times lower in the gas immediately surrounding HL Tauri if the CS emission is optically thin. The continuum and spectral line results obtained are strong indicators of conditions thought to be similar to those in the presolar nebula some 4.5 AE ago.

Blake, Geoffrey A.↗
NASA NTRS1969

Surface temperature mapping with infrared photographic pyrometry

Infrared photographic pyrometry method measures and maps the temperature distribution on a heated surface with accuracy and precision. This method involves the collection, detection and measurement of a narrow bandwidth of emitted infrared radiation. Standard commercially-available equipment is used, together with systematic procedures.

Pollack, F. G.↗
NASA NTRS1980

An automatic locating system for cloud-to-ground lightning

Automatic locating systems which respond to cloud to ground lightning and which discriminate against cloud discharges and background noise are described. Subsystems of the locating system, which include the direction finder and the position analyzer, are discussed. The direction finder senses the electromagnetic fields radiated by lightning on two orthogonal magnetic loop antennas and on a flat plate electric antenna. The position analyzer is a preprogrammed microcomputer system which automatically computes, maps, and records lightning locations in real time using data inputs from the direction finder. The use of the locating systems for wildfire management and fire weather forecasting is discussed.

Krider, E. P.↗
NASA NTRS1985

Observations from 1 to 20 microns of low-luminosity active galaxies

The 1-20 micron photometry of Liners (Low Ionization Nuclear Emission-line Regions), star burst nuclei, and high-excitation (mostly Seyfert 2) nuclei are presented and discussed. Liners have strong, flattish 10-20 micron excesses but are dominated by a stellar population through 1-5 micron. By contrast, most type 2 Seyfert galaxies and all star-burst nuclei have flux distributions that are flat through 1-5 microns, and steeply rising through 10-20 microns. The 1-5 micron flux distributions of type 2 Seyfert galaxies and starburst nuclei can be explained by mixtures of stellar emission, recombination radiation, and hot dust, although a nonthermal component is likely in a few objects. One Liner, NGC 3079, was found to be extended to 10 microns. A map which shows the 10-micron and optical maxima to differ by 6 arcsec is presented.

Lawrence, A.↗
NASA NTRS1986

IRAS observations of giant molecular clouds in the Milky Way

The IRAS data base has been used to study infrared radiation from molecular clouds in our galaxy. The sample of clouds was restricted to those with reliably determined molecular masses from large area, multi-isotope CO maps. They were normalized to X(CO-13)= 2x10 to the -6. Flux densities at 60 microns and 100 microns were determined by integrating the flux density within rectangles drawn on the sky flux plates after subtracting a suitable background. The rectangles were chosen to be coextensive with the areas mapped in CO. Color corrections were made and luminosites calculated by assuming the optical depths were proportional to frequency. The flux densities were converted to dust masses with a value for 4a rho/3Q = .04 g/cm at 100 microns.

Mozurkewich, D.↗
NASA NTRS1991

A nonthermal radio halo surrounding M82

Radio maps at several frequencies are presented which reveal an extended halo of nonthermal emission surrounding the starburst galaxy M82. The origin of this halo is probably synchrotron radiation from relativistic electrons originally produced in SNR, swept out of the disk by the extensive wind associated with the galaxy. The halo appears to be asymmetrical, with an enhancement occurring about 1 arcmin to the south, and on a larger scale there is excess emission to the north. Possible causes of this effect are addressed. The spectral index measured using data at 6, 20, 49, and 90 cm is about -0.4 + or - 0.1 in the nucleus, steepening to about -1.0 in the halo. A simple model is invoked which involves outward convection of relativistic particles with electron energy losses by inverse Compton scattering against IR photons and adiabatic expansion.

Seaquist, E. R.↗