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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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Raman mapping is utilized to constrain the spatial distribution of fine scale shock effects previously reported from TEM studies. These effects include residual oxides from the formation of magnetite in carbonate and incipient amorphous silica and orthopyroxene.
The NASA/Goddard Space Flight Center Scanning Raman Lidar has made measurements of water vapor and aerosols for almost ten years. Calibration of the water vapor data has typically been performed by comparison with another water vapor sensor such as radiosondes. We present a new method for water vapor calibration that only requires low clouds, and surface pressure and temperature measurements. A sensitivity study was performed and the cloud base algorithm agrees with the radiosonde calibration to within 10-15%. Knowledge of the true atmospheric lapse rate is required to obtain more accurate cloud base temperatures. Analysis of water vapor and aerosol measurements made in the vicinity of Hurricane Bonnie are discussed.
Hi-Nicalon fiber reinforced celsian matrix composites were characterized by Raman spectroscopy and imaging, using several laser wavelengths. Composite #1 is reinforced by as-received fibers while coatings of p-BN and SiC protect the fibers in composite #2. The matrix contains traces of the hexagonal phase of celsian, which is concentrated in the neighborhood of fibers in composite #1. Some free silicon was evident in the coating of composite #2 which might involve a {BN + SiC yields BNC + Si} "reaction" at the p-BN/SiC interface. Careful analysis of C-C peaks revealed no abnormal degradation of the fiber core in the composites.
The NASA/GSFC Scanning Raman Lidar (SRL) was stationed on Andros Island in the Bahamas during August - September, 1998 as a part of the third Convection and Moisture Experiment (CAMEX-3) which focussed on hurricane development and tracking. During the period August 21 - 24, hurricane Bonnie passed near Andros Island and influenced the water vapor and cirrus cloud measurements acquired by the SRL. Two drying signatures related to the hurricane were recorded by the SRL and other sensors. Cirrus cloud optical depths (at 351 nm) were also measured during this period. Optical depth values ranged from less than 0.01 to 1.5. The influence of multiple scattering on these optical depth measurements was studied. A correction technique is presented which minimizes the influences of multiple scattering and derives information about cirrus cloud optical and physical properties. The UV/IR cirrus cloud optical depth ratio was estimated based on a comparison of lidar and GOES measurements. Simple radiative transfer model calculations compared with GOES satellite brightness temperatures indicate that satellite radiances are significantly affected by the presence of cirrus clouds if IR optical depths are approximately 0.005 or greater. Using the ISCCP detection threshold for cirrus clouds on the GOES data presented here, a high bias of up to 40% in the GOES precipitable water retrieval was found.
Band shifts on Raman spectra were used to assess, at a microscopic scale, the residual strain existing in Hi-Nicalon fibers reinforcing celsian matrix composites. Uncoated as well as p-BN/SiC- and p-B(Si)N/SiC-coated Hi-Nicalon fibers were used as the reinforcements. We unambiguously conclude that the fibers are in a state of compressive residual stress. Quantitative determination of the residual stress was made possible by taking into account the heating induced by laser probing and by using a reference line, of fixed wavenumber. We found fiber compressive residual stress values between 110 and 960 MPa depending on the fiber/matrix coating in the composite. A stress relaxation-like phenomenon was observed at the surface of p-BN/SiC-coated Hi-Nicalon fibers whereas the uncoated or p-B(Si)N/SiC-coated Hi-Nicalon fibers did not show any stress relaxation in the Celsian matrix composites.
The detection of reduced carbon in martian rocks and soils is important in the search for evidence of life. A Raman spectroscopic study of South Africa chert reveals that 50 ppm carbon or less can be determined by this technique. Additional information is contained in the original extended abstract.
The Mars Microbeam Raman Spectrometer can identify minerals in situ, determine rock types and textures, provide some mineral chemistry, detect organic and biogenic materials, and identify bound water. Additional information is contained in the original extended abstract.
A Raman survey on a flat-sawn rock slab provides the major mineralogy of martian meteorite Los Angeles. Three unreported accessory minerals and seven terrestrial alteration products and contaminants (organic and inorganic) were also found. Additional information is contained in the original extended abstract.
Martian meteorite EETA79001 contains abundant Fe-Ti oxides, which yield Raman spectra useful for the assignment of their structural and compositional features. Additional information is contained in the original extended abstract.
Raman lidar profiles of aerosol extinction and water vapor are used to characterize the vertical variability of aerosols and water vapor over northern Oklahoma.
The Mars Microbeam Raman Spectrometer, under development at Washington University and the Jet Propulsion Laboratory, can identify oxide, sulfide, and oxyanion minerals, bound water and OH, and organic and graphitic carbon in Mars rocks and soils in situ. Additional information is contained in the original extended abstract.
We are currently developing an atomic oxygen diagnostic to study the degree of oxygen dissociation in ground-based facilities. The absorption of the (sub 3)P - (sup 3)S(sup 0) resonance triplet in the vacuum ultraviolet is a direct measure of the ground state number density of atomic oxygen. Although the integrated line strength is well known for these transitions, the line profile is not. We report the results of a series of experiments in which the line profile is measured in shock-heated oxygen. An ArF excimer laser and a hydrogen Raman shifter generate tunable VUV radiation at the resonance wavelength. The test gas is dissociated oxygen, generated in the Electric Arc Shock Tube (EAST) Facility at NASA-Ames Research Center. By measuring the absorption of known concentrations of atomic oxygen, we are able to study the absorption line profile. The results will serve as a calibration to apply this diagnostic in other flowfields.
The ion implantation in a crystal such as silicon carbide will cause both damage in the ion track and in the substrate at the end of the ion track. We used both keV, and MeV Pd ions in fabricating electronic chemical sensors in silicon carbide, which can operate at elevated temperatures. In order to study the feasibility of fabricating an optical chemical sensor (litmus sensor), we need to understand the optical behavior of the embedded damage in the presence of hydrogen, as well as the potential chemical interaction of silicon carbide broken lattice bonds with the hydrogen dissociated from gas by palladium. Implanted samples of silicon carbide were studied using both Raman spectroscopy and FTIR (Fourier Transform-Infrared). The results of this work will be presented during the meeting.
The NASA/GSFC Scanning Raman Lidar (SRL) was deployed to the Department of Energy's (DOE) Cloud and Radiation Testbed site in northern Oklahoma September - December, 2000 for two DOE sponsored field campaigns: 1) the Water Vapor Intensive Operations Experiment 2000 and 2) the Atmospheric Radiations Measurement First International Satellite Cloud Climatology Experiment Experiment (AFWEX). WvIOP2000 focussed on water vapor measurements in the lower troposphere while AFWEX focussed on upper tropospheric water vapor. For the first time ever, four water vapor lidars were operated simultaneously: one airborne and three ground-based systems. Intercomparisons of these measurements and others will be presented at the meeting.
An understanding of the structural and compositional controls on the Raman features of the major types of phyllosilicates is presented. Additional information is contained in the original extended abstract.
Last May, a rover field test was conducted in the Mojave desert. This study shows what mineralogy a rover-deployed Raman spectrometer might have observed. Additional information is contained in the original extended abstract.
A breadboard of a miniaturized, simple, robust, easily deployed laser microbeam Raman spectrometer for on-surface mineralogy and carbon and water detection has been built. Here is what it can do on rocks. Additional information is contained in the original extended abstract.
In this paper, we explore the use of remote LIBS combined with pulsed-laser Raman spectroscopy for mineral analysis at a distance of 10 meters. Samples analyzed include: carbonates (both biogenic and abiogenic), silicates, and sulfates. Additional information is contained in the original extended abstract.