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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 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

Two-beam interferometer for optical constants measurements at near-millimeter wavelengths

A simple and versatile instrument for the measurement of optical constants in the near millimeter spectral region is described. Studies of quasi-optical components used in this instrument for effective beam transmission and control are reported. These studies include transmission characteristics of dielectric waveguides and performance of a variable coupler based on frustrated total internal reflection. Operation of this instrument as a two-beam interferometer for determining the index of refraction or as a device to measure transmission for determining the absorption coefficient are described. Values measured with this instrument at 245 GHz, using an optically pumped molecular laser as the source, are reported for several low-loss materials. Appropriate corrections and error estimates are discussed. The potential for improvement and increased accuracies are discussed.

Jones, C. R.↗
NASA NTRSDate not supplied

Assessing Uncertainties and Variability 34 Years of Surface Radiative Fluxes Using GEWEX SRB Release4-IP

The NASA/GEWEX Surface Radiation Budget (SRB) project produces 3-hrly shortwave and longwave surface and top of atmosphere radiative fluxes for the 1983-near present time period. The new Release 4 Integrated Product (IP) uses the newly recalibrated and processed ISCCP HXS product as its primary input for cloud and radiance data, replacing ISCCP DX with a ninefold increase in pixel count (10 km instead of 30 km). This first version retains a 1°x1° resolution enabling intercomparison against previous versions and other data sets such as CERES, but spans 34 years from July 1983 through June 2017 and was announced by Kummerow et al. 2019 (GEWEX News). This new IP product also uses an atmospheric temperature and moisture dataset known as nnHIRS and other parameters such as near surface and skin temperatures from SeaFlux and LandFlux data sets. In addition to the input data improvements, several important algorithm improvements have been made since Release 3. These include recalculated SW atmospheric transmissivities and reflectivities, updated ocean and snow/ice albedos, and variable total solar irradiance consistent with SORCE measurements. The LW code has been updated to improve the optical property treatment for clouds and aerosols are included in this version. Radiative treatment of ice clouds is also improved in the LW. The variable aerosol optical properties for the SW and LW are specified using a detailed aerosol history from the Max Planck Institute Aerosol Climatology (MAC). Here we present an assessment of the LW radiative fluxes and the uncertainty of those fluxes relative to the various inputs to surface SW/LW flux measurements from BSRN and PMEL buoys measurements. We review the validation of the SW and LW fluxes and then in terms of time series and then assess the products in terms of their long-term variability of the surface SW and LW net fluxes compared to multiple other data products including atmospheric reanalysis products. The comparisons of radiative estimates to observations are performed at various temporal scales and aimed at investigation of agreement at longer time averages but accessing potential change in diurnal magnitude and daily variability. Utilizing this uncertainty information, to access long-term variability of surface radiation components at selected region and global scales, considering satellite sampling/calibration “artifacts” as necessary. At the longer time scales, the net SW and net LW the TOA and surface have implications toward closure of the energy budgets at the surface, we assess these compared to other studies on energy budget closure for the same selected global and regional scales.

Paul W Stackhouse↗
NASA NTRS1990

Planetary astronomy of Mars. Mars data reduction

Grant #NAGW-1408 was specifically awarded to obtain telescopic visible and near-IR spectral imaging of Mars during the 1988 apparition (9/28/88). The observing program was highly successful producing approximately 2 Gbytes of data, but was only funded for one year and virtually all of the funds were spent in data acquisition. The follow-up grant was funded the following year for reduction of these data into a scientifically productive form, which because of the size and nature of our observations, was a non-trivial task. A more detailed scientific analysis of these data (fully reduced) is in progress now and will take a number of years. Extended geologic analyses of the astronomical data are being funded by the NASA Planetary Geology and Geophysics program. The objective was to produce detailed reflectance spectra for contiguous, spatially resolved surface elements covering most of the planet (about +50 degrees to -90 degrees latitude, all longitudes). A total of 6 observing runs, of 3-4 days duration each, were conducted on the University of Arizona's 1.5m telescope on Mt. Bigelow. We present a sketch map showing the approximate total extent of our spectral image coverage. Nearly all of Mars south of 40 degrees N was observed at least once. About half of the area shown was observed multiple times. South of 65 degrees S, including the south polar cap, our coverage is heavily redundant. The first run was conducted June 29 - July 1, 1988 (all dates are UT) to serve as a baseline prior to possible dust storm activity on Mars. The other observing runs were closer to opposition: Sept. 3-6, 13-15, 24-26, and Oct. 5-7 and 16-18. The September and October observations were scheduled to provide maximum longitudinal coverage. This was also intended to provide a balance between surface observations and observations of predicted dust storm activity. No global dust storm developed in 1988, so we have a large volume of data for the surface of Mars.

Singer, Robert B.↗
NASA NTRS1973

The Nimbus-4 backscatter ultraviolet (BUV) atmospheric ozone experiment two years operation

The Backscatter Ultraviolet (BUV) experiment aboard the Nimbus-4 satellite is discussed. This double monochromator experiment measures ultraviolet terrestrial radiance at 12 discrete wavelengths between 2550 A and 3400 A. Approximately 100 scans covering a 230 kilometer square are made between terminator crossings on the daylight side of the earth. A colinear photometer channel with the same field of view is used to derive the Lambert reflectivity of the lower boundary of the scattering atmosphere. The extraterrestrial solar irradiance is measured at the northern terminator. The instrument has currently produced almost three years of nearly continuous data which are being used to infer the high-level ozone distribution and total ozone on a global basis. The high-level ozone data have been verified by independent coincident rocket ozone soundings, and the total ozone values show good agreement with Dobson spectrophotometer determinations as well as those made with the Infrared Interferometer Spectrometer also on Nimbus-4.

Heath, D. F.↗
NASA NTRS1999

The Radio Plasma Imager Investigation on the IMAGE Spacecraft

Radio plasma imaging uses total reflection of electromagnetic waves from plasmas whose plasma frequencies equal the radio sounding frequency and whose electron density gradients are parallel to the wave normals. The Radio Plasma Imager (RPI) has two orthogonal 500-m long dipole antennas in the spin plane for near omni-directional transmission. The third antenna is a 20-m dipole. Echoes from the magnetopause, plasmasphere and cusp will be received with three orthogonal antennas, allowing the determination of their angle-of-arrival. Thus it will be possible to create image fragments of the reflecting density structures. The instrument can execute a large variety of programmable measuring programs operating at frequencies between 3 kHz and 3 MHz. Tuning of the transmit antennas provides optimum power transfer from the 10 W transmitter to the antennas. The instrument can operate in three active sounding modes: (1) remote sounding to probe magnetospheric boundaries, (2) local (relaxation) sounding to probe the local plasma, and (3) whistler stimulation sounding. In addition, there is a passive mode to record natural emissions, and to determine the local electron density and temperature by using a thermal noise spectroscopy technique.

Reinisch, Bodo W.↗
NASA NTRS1986

Comparison of in situ measurements of forest decline symptoms in Vermont (USA) and the Schwarzwald (FRG)

Field analyses were conducted at spruce/fir sites in the U.S. and Germany undergoing forest decline. Data gathered from common branch samples included reflectance curves, fluorescence measurements, and pigment concentrations. Similar reflectance signatures are seen for specimens from all sites. Reflectance spectra from specimens collected from high damage sites in both countries show a characteristic reflectance drop in the near infrared and a shift (5 nm) of the red edge to shorter wavelengths. Fluorescence data suggest altered state of health of photosynthetic pigments only in specimens from German high damage sites, and pigment extraction and analysis indicate a reduction in total chlorophyll, a decrease in chlorophyll b when compared with chlorophyll a, and a relative increase in carotenoids.

Rock, B. N.↗
NASA NTRS1992

Energy and radiation balance components for three grass surfaces near Kursk, Russia

The energy and radiation balance components were determined over three grass surfaces, located on the Streletskaya steppe during July 1991. The Bowen ratio energy balance method was used to determine the sensible and latent heat flux densities using six computer controlled systems. A total of 126 variables were sampled, including global, diffuse, and reflected solar radiation, long wave radiation (up and down), net radiation, photosynthetically active radiation above and below the vegetation, infrared surface temperatues, soil temperature and heat flow, air temperature and vapor pressure at two levels, wind speed and direction, and precipitation. The ranking of the sites from greatest to smallest for net radiation and latent heat flux density were preserve, mowed in 1990, and mowed in 1991. The ranking of the sites from greatest to smallest for sensible heat flux density were mowed in 1990, mowed in 1991, and preserve.

Fritschen, Leo J.↗
NASA NTRSDate not supplied

Calibration of Landsat 8 Aquatic Reflectance Band Data to Spatial Variations in Chlorophyll a, Suspended Sediment, N, and P in Coastal Estuaries of Southern Louisiana

Nutrient enrichment of coastal estuaries is a proven causal agent of harmful algal blooms, fish kills, and hypoxic zones. To enable regional mapping in coastal estuaries of southern Louisiana of Chlorophyll a, suspended sediment, N, and P concentrations, monthly water sample data collected at over 30 stations along a 129 km transect in the Barataria Basin by Turner et al. (2019) were correlated with Landsat 8 aquatic reflectance (ar) band 3 and 4 image data (2013-2016). Results showed significant non-linear correlations (R2 > 0.2) of Landsat ar band 4 values with measured concentrations of Chlorophyll a, total suspended sediment, N, and P. The strongest correlations were revealed between Landsat ar band 4 reflectances and total P concentrations, periodically at R2 values > 0.6. Landsat ar band images revealed detailed variations in total N and P concentrations that were consistent with the measured nutrient declines associated with dilution of freshwater as sampling locations progressed toward more coastal saline waters. Regional map images of ar band 4 in 2019 and 2020 confirmed that recent openings of Bonnet Carre Spillway could have resulted in damage to oyster beds in the brackish Gulf waters near Lake Borgne and the Mississippi River Delta, possibly due to reduced salinity levels and enhanced sediment deposition.

Calibration↗
NASA NTRS1977

Remote sensing of the atmosphere from environmental satellites

Various applications of satellite remote sensing of the earth are reviewed, including (1) the use of meteorological satellites to obtain photographic and radiometric data for determining weather conditions; (2) determination of the earth radiation budget from measurements of reflected solar radiation and emitted long wave terrestrial radiation; (3) the use of microwave imagery for measuring ice and snow cover; (4) LANDSAT visual and near infrared observation of floods and crop growth; and (5) the use of the Nimbus 4 backscatter ultraviolet instrument to measure total ozone and vertical ozone distribution. Plans for future activities are also discussed.

Allison, L. J.↗
NASA NTRS2007

Aerosol Source Plume Physical Characteristics from Space-based Multiangle Imaging

Models that assess aerosol effects on regional air quality and global climate parameterize aerosol sources in terms of amount, type, and injection height. The multiangle imaging spectroradiometer (MISR) aboard NASA's Terra satellite retrieves total column aerosol optical thickness (AOT), and aerosol type over cloud-free land and water. A stereo-matching algorithm automatically retrieves reflecting-layer altitude wherever clouds or aerosol plumes have discernable spatial contrast, with about 500-m accuracy, at 1.1-km horizontal resolution. Near-source biomass burning smoke, volcanic effluent, and desert dust plumes are observed routinely, providing information about aerosol amount, particle type, and injection height useful for modeling applications. Compared to background aerosols, the plumes sampled have higher AOT, contain particles having expected differences in Angstrom exponent, size, single-scattering albedo, and for volcanic plume and dust cloud cases, particle shape. As basic thermodynamics predicts, thin aerosol plumes lifted only by regional winds or less intense heat sources are confined to the boundary layer. However, when sources have sufficient buoyancy, the representative plumes studied tend to concentrate within discrete, high-elevation layers of local stability; the aerosol is not uniformly distributed up to a peak altitude, as is sometimes assumed in modeling. MISR-derived plume heights, along with meteorological profile data from other sources, make it possible to relate radiant energy flux observed by the moderate resolution imaging spectroradiometer (MODIS), also aboard the Terra spacecraft, to convective heat flux that plays a major role in buoyant plume dynamics. A MISR climatology of plume behavior based on these results is being developed.

aerosol plumes↗
NASA NTRS1978

Evaluation of glass resin coatings for solar cell applications

Using a variety of non-vacuum deposition techniques coatings were implemented on silicon solar cells and arrays of cells interconnected on Kapton substrates. The coatings provide both antireflection optical matching and environmental protection. Reflectance minima near 2% was achieved at a single wavelength in the visible. Reflectance averaging below 5% across the useful collection range was demonstrated. The coatings and methods of deposition were: (1) Ta2O5 spun, dipped or sprayed; (2) Ta2O5.SiO2 spun, dipped or sprayed; (3) GR908 (SiO2) spun, dipped, or sprayed. Total coating thickness were in the range of 18 microns to 25 microns. The coatings and processes are compatible with single cells or cells mounted on Kapton substrates.

Field, M. B.↗
NASA NTRS1991

Retrieval of total precipitable water over high latitude regions using radiometric measurements near 90 and 183 GHz

The functional dependence of brightness temperature, at frequencies near 183 and 90 GHz, on total precipitable water in the range less than 0.5 g/cm is examined by means of radiative transfer calculations of a number of observed temperature and relative humidity profiles over both ocean and land surfaces. A wide range of land and sea surface reflectivities is assumed in the calculations. Both sensitivity and precision of total precipitable water estimates are derived from these calculations. The estimated values in the Southern Hemisphere showed a gradual decrease toward the polar region, as expected. Radiative transfer calculations were made with a number of radiosonde data sets for a wide range of surface reflectivity and temperature. The calculated results are used to estimate total precipitable water from the airborne radiometric measurements over Alaska. Reflectivities at both 92 and 193 GHz are found to be mostly in the range of 0.2-0.4. High reflectivity is attributed to scattering by the snow particles on the ground.

Wang, J. R.↗
NASA NTRS1990

A parameterization for the shortwave transmissivity of stratiform water clouds based on empirical data and radiative transfer theory

Surface measurements of solar flux and total integrated liquid-water content, radiosonde data, and infrared satellite images are analyzed in conjunction with radiative transfer calculations to derive an empirical parameterization for the shortwave transmissivity of continental stratiform water clouds. The data were collected near Denver, Colorado, over a period of six years. A multiple reflection radiative transfer model is employed to estimate stratus cloud transmissivity in terms of the measurable liquid-water path (LWP). A nonlinear fit of estimated transmissivities to the corresponding observations of LWP yields close agreement with a previous, more complicated parameterization. The derived expression for cloud transmissivity is used to predict mean daily surface fluxes for 61 days during which periods of stratiform clouds were observed over the Denver area. A comparison between predicted and measured fluxes shows agreement to within + or - 4 percent, with best agreement for clouds of moderate optical thickness. Potential sources of error are identified with sensitivity studies.

Derr, V. E.↗
NASA NTRS1992

Remote sensing of water vapor in the near IR from EOS/MODIS

Consideration is given to the selection of spectral channels in the near-infrared IR which are to be employed for the derivation of total column water vapor using the MODIS instrument on the NASA's Earth Observing System. Data obtained show that the three near-IR water vapor channels on the MODIS instrument enable remote sensing of the total column water vapor with an absolute accuracy of +/- 13 percent. An absolute accuracy of +/-7 percent can be obtained if additional MODIS channels are used to decrease the effect of uncertainty in the spectral reflectance of the surface, subpixel clouds, haze, and temperature profile on the derived water vapor.

Kaufman, Yoram J.↗
NASA NTRS1997

An Assessment of Ozone Photochemistry in the Extratropical Western North Pacific: Impact of Continental Outflow During the Late Winter/Early Spring

This study examines the influence of photochemical processes on tropospheric ozone distributions over the extratropical western North Pacific. The analysis presented here is based on data collected during the Pacific Exploratory Mission-West Phase B (PEM-West B) field study conducted in February-March 1994. Sampling in the study region involved altitudes of 0-12 km and latitudes of 10deg S to 50deg N. The extratropical component of the data set (i.e., 20-50deg N) was defined by markedly different photochemical environments north and south of 30deg N. This separation was clearly defined by an abrupt decrease in the tropopause height near 30deg N and a concomitant increase in total O3 column density. This shift in overhead O3 led to highly reduced rates of O3 formation and destruction for the 30-50deg N latitude regime. Both latitude ranges, however, still exhibited net O3 production at all altitudes. Of special significance was the finding that net O3 production prevailed even at boundary layer and lower free tropospheric altitudes (e.g., less than 4 km), a condition uncommon to Pacific marine environments. These results reflect the strong impact of continental Outflow of O3 precursors (e.g., NO and NMHCS) into the northwestern Pacific Basin. Comparisons with PEM-West A, which sampled the same region in a different season (September-October), revealed major differences at altitudes below 4 km, the altitude range most influenced by continental outflow. The resulting net rate of increase in the tropospheric O3 column for PEM-West B was 1-3 % per day, while for PEM-West A it was approximately zero. Unique to the PEM-West B study is the finding that even under wintertime conditions substantial column production of tropospheric O3 can occur at subtropical and mid-latitudes. While such impacts may not be totally unexpected at near coast locations, the present study suggests that the impact from continental outflow on the marine BL could extend out to distances of more than 2000 km from the Asian Pacific Rim.

Crawford, J.↗
NASA NTRS2003

Sensitivity Studies for Space-based Measurement of Atmospheric Total Column Carbon Dioxide Using Reflected Sunlight

A series of sensitivity studies is carried out to explore the feasibility of space-based global carbon dioxide (CO2) measurements for global and regional carbon cycle studies. The detection method uses absorption of reflected sunlight in the CO2 vibration-rotation band at 1.58 microns. The sensitivities of the detected radiances are calculated using the line-by-line model (LBLRTM), implemented with the DISORT (Discrete Ordinates Radiative Transfer) model to include atmospheric scattering in this band. The results indicate that (a) the small (approx.1%) changes in CO2 near the Earth's surface are detectable in this CO2 band provided adequate sensor signal-to-noise ratio and spectral resolution are achievable; (b) the radiance signal or sensitivity to CO2 change near the surface is not significantly diminished even in the presence of aerosols and/or thin cirrus clouds in the atmosphere; (c) the modification of sunlight path length by scattering of aerosols and cirrus clouds could lead to large systematic errors in the retrieval; therefore, ancillary aerosol/cirrus cloud data are important to reduce retrieval errors; (d) CO2 retrieval requires good knowledge of the atmospheric temperature profile, e.g. approximately 1K RMS error in layer temperature; (e) the atmospheric path length, over which the CO2 absorption occurs, must be known in order to correctly interpret horizontal gradients of CO2 from the total column CO2 measurement; thus an additional sensor for surface pressure measurement needs to be attached for a complete measurement package.

Mao, Jianping↗
NASA NTRS1980

Spectral reflectance and discrimination of plutonic rocks in the 0.45- to 2.45-micron region

Visible and near-infrared field spectral reflectance measurements of plutonic rocks were acquired in the 0.45- to 2.45-micron region with a portable field reflectance spectrometer. These spectra were used to determine spectral signatures for the various rock types and to evaluate the separability of these rocks based on their spectral characteristics. A total of 135 samples were divided into 11 groups based on their mineralogy. These 11 groups approximately correspond to traditional rock classifications and include five granitic groups, three gabbroic groups, and three ultramafic groups. The positions, intensity, and presence of iron, CO3(-2), and Al-OH and Mg-OH absorption bands varied among the 11 groups. Each rock group also had a range of albedos characteristic of the group. Stepwise linear discriminant analysis was performed on the spectral data to determine the separability of the 11 groups. Classification accuracy for 30 equally spaced wavelength bands between 0.45 and 2.45 microns was 78% with 10% serious misclassifications. The same analysis was repeated, limiting the spectral data to the wavelength regions corresponding to the proposed Landsat D thematic mapper scanner.

Blom, R. G.↗
NASA NTRS2004

Discoveries about Tropospheric Ozone Pollution from Satellite and Soundings

We have been producing near-red time tropospheric ozone satellite maps from the TOMS (Total Ozone Mapping Spectrometer) sensor since 1997. Maps for 1996-2000 for the operational Earth-Probe instrument are at: . Pollution in the tropics is influenced by biomass burning and by transport patterns that favor recirculation and in other cases reflect climate variability like the El-Nino-Southern Oscillation [Thompson et al., 2001]. The satellite view of chemical-dynamical interactions in tropospheric ozone is not adequate to capture vertical gradients in pollution. Thus, in 1998, NASA's Goddard Space Flight Center and a team of international sponsors established the SHADOZ (Southern Hemisphere ADditional OZonesondes) project to address the gap in tropical ozone soundings. SHADOZ augments launches and provides a public archive of ozonesonde data from twelve tropical stations at http://croc.gsfc.nasa.gov/shadoz. Further insights into the role of chemical and dynamical influences have emerged from the first 4-5 years of SHADOZ data (more than 2000 ozone profiles). Highly variable tropospheric ozone and a zonal wave-one pattern in tropospheric ozone suggest that dynamics is as important as pollution in determining tropical ozone distributions.

Thompson, Anne M.↗