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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 217 records · Page 12
All sourcesNASA NTRSDOE OSTI
NASA NTRS1981

The C I opacity and physical structure of cool, very dense plasma in the solar corona

The physical structure of the cool material in the volume of the solar corona is investigated. The observational evidence is summarized in a table giving the brightness contrast in optical and EUV radiations. The state of ionization and the opacity sources are discussed, and a physical model is described that is consistent with the EUV and optical data. It is noted that a comparison of the EUV raster pictures with H-alpha and Ca K photoheliograms indicates that the material is commonly injected from below into relatively low-lying magnetic loops (fibrils) seen near sunspots and plages.

Foukal, P.↗
NASA NTRS1981

Sulfur dioxide and other cloud-related gases as the source of the microwave opacity of the middle atmosphere of Venus

Spacecraft radio occultation measurements imply the presence of a nonuniformly mixed gaseous absorber within, but mostly below, the main cloud layer of sulfuric acid-water droplets measured by Pioneer-Venus. Preliminary considerations of the amount, distribution, and effects of sulfur dioxide and other gases, which apparently are associated with and produce the cloud, indicate that they constitute an important, and probably the predominant, source of the observed microwave opacity of the middle atmosphere of Venus.

Steffes, P. G.↗
NASA NTRS1981

Mars atmospheric opacity effects observed in the Northern Hemisphere by Viking orbiter imaging

Viking orbiter television camera observations of Mars contrasts show variations of atmospheric opacity in the Southern Hemisphere. The study is extended into the Northern Hemisphere, over a longer time period, and results in a detailed description of photometric changes at the lander sites, as seen from orbit. During the period of January 1977 to April 1978, a series of four storms at 202 deg, 264 deg, 40 deg and 86 deg latitudes have provided photometric changes and planetwide aerosol distributions for 18 months. It is found that the large, forward-scattering particles did not enter the atmosphere at the storm's onsets. A reduction of atmospheric transmission by over 20% at visual wavelengths remained for nearly one Martian year.

Thorpe, T. E.↗
NASA NTRS1986

Retrieval of ammonia abundances and cloud opacities on Jupiter from Voyager IRIS spectra

Gaseous ammonia abundances and cloud opacities are retrieved from Voyager IRIS 5- and 45-micron data on the basis of a simplified atmospheric model and a two-stream radiative transfer approximation, assuming a single cloud layer with 680-mbar base pressure and 0.14 gas scale height. Brightness temperature measurements obtained as a function of emission angle from selected planetary locations are used to verify the model and constrain a number of its parameters.

Conrath, B. J.↗
NASA NTRS1987

Opacity project - Astrophysical and fusion applications

An overview is presented of a project to calculate large quantities of accurate atomic data for radiative processes of importance in the precise determination of opacities in stellar atmospheres, and for astrophysical and laboratory applications in general. Work is in progress on the oscillator strengths, photoionization cross sections, damping constants, etc., for all atoms and ions in hydrogen through neon isoelectronic sequences going up to iron.

Pradhan, A. K.↗
NASA NTRS1987

Laboratory measurements of the microwave opacity of gaseous ammonia (NH3) under simulated conditions for the Jovian atmosphere

Microwave opacity measurements have been conducted for gaseous ammonia simulating Jovian atmosphere conditions at five frequencies from 18.5 to 1.38 cm, at temperatures from 178 to 300 K and 1-6 atm pressures. The atmospheric composition is 90-percent H/10-percent He. In the 1.38-18.5 cm wavelength range, ammonia absorption is well expressed by Berge and Gulkis' (1976) lineshape. The results obtained suggest that either an ammonia abundance 1.5-2.0 times greater than solar must be present at less than 1-2 bar, or some other microwave absorber is present.

Steffes, Paul G.↗
NASA NTRS1987

OH and CH continuous opacity in solar and stellar atmospheres

Continuous absorption cross sections of OH and CH have been computed for the temperature range 1000 K to 9000 K. Both OH and CH produce significant ultraviolet opacity in the sun and cool stars. CH is also significant in the visible at 400 nm.

Kurucz, Robert L.↗
NASA NTRS1989

Analytical expressions for the Rosseland-mean opacity and electron scattering in stellar atmospheres

Simple analytical approximations for the calculations of the electron scattering coefficient, the Rosseland-mean opacity and the equation of state in the temperature range of 4000 to 50,000 K and the density range of 10 to the -13th to 10 to the -7th g/cu cm. These approximations are valid for a gas with 1, 0.1, and 0.01 times the solar metal abundances in LTE. The accuracy of the approximations is better than 5 percent over most of this temperature and density range.

Burger, P.↗
NASA NTRS1992

Laboratory measurements of the microwave and millimeter-wave opacity of gaseous sulfur dioxide (SO2) under simulated conditions for the Venus atmosphere

Laboratory measurements have been conducted of the opacity of gaseous SO2 in a CO2 atmosphere at 12.3 cm, 1.32 cm, and 0.32 cm, with a view to the effects of this gas on the mm-wave emission of the Venus atmosphere. Close agreement is noted between the results obtained and the absorptivity predicted from a Van Vleck-Weisskopf formalism at the two shortest wavelengths, but not at the longest. These results have been incorporated into a radiative transfer model in order to infer an abundance profile for gaseous SO2 in Venus' middle atmosphere, and are also used to ascertain the effects of a SO2/CO2 gaseous mixture on the mm-wavelength spectrum of Venus.

Fahd, Antoine K.↗
NASA NTRS1993

Evidence for dust transport in Viking IR thermal mapper opacity data

Global maps of 9-micron dust opacity derived from radiometric observations made by the Viking Orbiter IR Thermal Mapper instruments have revealed a wealth of new information about the distribution of airborne dust over 1.36 Mars years from 1976-1979. In particular, the changing dust distribution during major dust storms is of interest since the data provide a point of contact with both Earth-based observations of storm growth and with global circulation models.

Martin, Terry Z.↗
NASA NTRS1996

Development of a solar-cell dust opacity measurement instrument for Mars Pathfinder

The atmosphere of Mars has a considerable load of suspended dust. Over time, this dust is deposited out of the atmosphere. The mechanism and the temporal and geographical variation of this deposition are not well characterized. Measurements of settling rates and dust properties are of considerable scientific interest. Atmospheric dust affects the atmospheric solar absorption and thus the heat balance of Mars, as well as serving as nucleation sites for water and CO2 frost. Knowledge of dust properties is of critical interest to design and prediction of the lifetime and power output of solar arrays, and also to design of mechanical mechanisms and radiators. An instrument has been designed and fabricated to measure the dust accumulation during the course of the Mars Pathfinder rover mission. The solar-cell coverglass transmission experiment will measure the change in optical opacity of a transparent coverglass as dust settles on the surface, and a quartz crystal monitor will measure the mass deposited.

Geoffrey A. Landis↗
NASA NTRS1999

Development of Prototype Micro-Lidar using Narrow Linewidth Semiconductor Lasers for Mars Boundary Layer Wind and Dust Opacity Profiles

We have developed a compact Doppler lidar concept which utilizes recent developments in semiconductor diode laser technology in order to be considered suitable for wind and dust opacity profiling in the Mars lower atmosphere from a surface location. The current understanding of the Mars global climate and meteorology is very limited, with only sparse, near-surface data available from the Viking and Mars Pathfinder landers, supplemented by long-range remote sensing of the Martian atmosphere. The in situ measurements from a lander-based Doppler lidar would provide a unique dataset particularly for the boundary layer. The coupling of the radiative properties of the lower atmosphere with the dynamics involves the radiative absorption and scattering effects of the wind-driven dust. Variability in solar irradiance, on diurnal and seasonal time scales, drives vertical mixing and PBL (planetary boundary layer) thickness. The lidar data will also contribute to an understanding of the impact of wind-driven dust on lander and rover operations and lifetime through an improvement in our understanding of Mars climatology. In this paper we discuss the Mars lidar concept, and the development of a laboratory prototype for performance studies, using, local boundary layer and topographic target measurements.

Menzies, Robert T.↗
NASA NTRS2001

Research on Spectroscopy, Opacity, and Atmospheres

With this funding I produced a web site kurucz.harvard.edu that can also be accessed by FTP. it has a 73GB disk that holds all of my atomic and diatomic molecular data, my tables of distribution function opacities, my grids of model atmospheres, colors, fluxes, etc., my programs that are ready for distribution, and most of my recent papers. Atlases and computed spectra will be added as they are completed. New atomic and molecular calculations will be added as they are completed.

Kurucz, Robert L.↗
NASA NTRS2003

Calculation of Free-Free Opacities

Free-free absorption is an important contribution to the opacity for radiation transport through hot materials Temperatures can be as high as several keV, such that it becomes a computational challenge to solve the Schrodinger equation efficiently for rapidly oscillating continuum functions for high angular momenta. Several groups\footnots, including ours, have studied the phase amplitude solution (PAS) of the Schrodinger equation, in which one solves equations for the wave function amplitude and phase, which are: smooth functions of the electron energy. It is also important to have an accurate Schroudinger benchmark for the development of the PAS method. We present results for dipole matrix elements, Gaunt factors, and cross sections for the absorption of radiation at various energies for Cs XIX at temperature=100 eV and density=0.187 g/cc for our newly developed PAS and Schrodinger benchmark.

Bhatia, A. K.↗
NASA NTRS2002

Molecular Line and Continuum Opacities for Modeling of Extrasolar Giant Planet and Cool Stellar Atmospheres

The molecular line and continuum opacities are investigated in the atmospheres of cool stars and Extrasolar Giant Planets (EGPs). Using a combination of ab inito and experimentally derived potential curves and dipole transition moments, accurate data have been calculated for rovibrationally-resolved oscillator strengths and photodissociation cross sections in the B' (sup 2)Sigma+ (left arrow) X (sup 2)Sigma+ and A (sup 2)Pi (left arrow) X (sup 2)Sigma+ band systems in MgH. We also report our progress on the study of the electronic structure of LiCl and FeH.

Weck, P. F.↗
NASA NTRS2011

NASCA Report 2: Longitudinal Study of Relationship of Exposure to Space Radiation and Risk of Lens Opacity

The NASA Study of Cataract in Astronauts (NASCA) was a five-year longitudinal study of the effect of space radiation exposure on the severity/progression of nuclear (N), cortical (C), and posterior subcapsular (PSC) lens opacities. It began in 2003 and was completed in December, 2009. Participants included 171 consenting astronauts who flew at least one mission in space, and comparison subjects consisted of three groups, a) 53 astronauts who had not flown in space, b) 95 military aircrew personnel, and c) 99 non-aircrew, ground-based subjects.

Chylack, Leon T., Jr.↗
NASA NTRS2010

Characterization of Forest Opacity Using Multi-Angular Emission and Backscatter Data

This paper discusses the results from a series of field experiments using ground-based L-band microwave active/passive sensors. Three independent approaches are employed to the microwave data to determine vegetation opacity of coniferous trees. First, a zero-order radiative transfer model is fitted to multi-angular microwave emissivity data in a least-square sense to provide "effective" vegetation optical depth. Second, a ratio between radar backscatter measurements with the corner reflector under trees and in an open area is calculated to obtain "measured" tree propagation characteristics. Finally, the "theoretical" propagation constant is determined by forward scattering theorem using detailed measurements of size/angle distributions and dielectric constants of the tree constituents (trunk, branches, and needles). The results indicate that "effective" values underestimate attenuation values compared to both "theoretical" and "measured" values.

Kurum, Mehmet↗
NASA NTRS2012

A Determination of the Intergalactic Redshift Dependent UV-Optical-NIR Photon Density Using Deep Galaxy Survey Data and the Gamma-Ray Opacity of the Universe

We calculate the intensity and photon spectrum of the intergalactic background light (IBL) as a function of red shift using an approach based on observational data obtained at in different wavelength bands from local to deep galaxy surveys. Our empirically based approach allows us, for the firs.t time, to obtain a completely model independent determination of the IBL and to quantify its uncertainties. Using our results on the IBL, we then place upper and lower limits on the opacity of the universe to gamma-rays, independent of previous constraints.

Stecker, Floyd W.↗