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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 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1972

Meteorological and ecological monitoring of the stratosphere and mesosphere

A concept for determining the constituent densities of ozone, atomic oxygen, aerosols, and neutral density in the 20 to 1000 km region of the atmosphere from a satellite was developed. The concept includes the daytime measurement of solar scattering at the earth's limb in selected narrow spectral bands of the ultraviolet and visible regions, and the measurement of selected (dayglow) emissions. Nighttime measurements of the atmospheric extinction of stellar energy in selected bands are also considered as are simultaneous measurements of the 5577 airglow and molecular oxygen emission in the Herzberg band. Radiative-transfer models and recursive inversion algorithms are developed for the measurements, and the accuracy of the concept is assessed.

Newell, R. E.↗
NASA NTRS1987

Identification and spectral characteristics of hydrothermal alteration on Landsat TM imagery of north Chile

This study examines the application of Landsat TM data to the identification of hydrothermal alteration in the arid terrain of the El Salvador region of north Chile. Numerical reflectance values were extracted from the digital Landsat TM data for a variety of rock surfaces, including four parts of the El Salvador gossan, for each of six spectral bands. These reflectance values were analyzed statistically in order to select the three spectral bands, combined as a color composite image, that are most efficient in discriminating different varieties of alteration and for general geological interpretation. The most cost effective composite image for this area is a combination of bands 1, 4 and 7 as the blue, green and red components respectively, with simple contrast enhancement. This image is superior to some much more expensive enhancement techniques and allows unambiguous identification of areas of hydrothermal alteration larger than about 50 m. The display includes a practical guide to the use of Landsat TM imagery for volcanic gold exploration.

Baker, Michael C. W.↗
NASA NTRS1972

Pulsed electromagnetic gas acceleration

Photographs of the exhaust plume of a pulsed MPD discharge through selected narrow band spectral filters reveal a species structure related to the location of the argon mass injection ports. This species structure provides the key to interpretation of time-resolved interferometric velocity measurements in the exhaust. The resulting exhaust velocity increases monotonically from 8500 m/sec at a position 5 cm downstream of the anode face to 16,500 m/sec 40 cm downstream. The latter value is approximately twice the Alfven critical speed for argon. The growth of the axial electric field near the downstream face of the anode indicates that the discharge operates in a starved mode. Data from biased double probes imply an electron temperature of 0.8 eV in the exhaust plume.

Jahn, R. G.↗
NASA NTRS1971

Reflectance and transmittance characteristics of several selected green and blue-green unialgae.

Obtained reflectance properties of green and blue-green unialgae are evaluated for determining the feasibility of using selected wavelengths in differentiating between green and blue-green algae. The attempt is made to establish selected wavelengths and ratios that would delineate relative concentrations of the algal suspensions. The results should prove helpful in the selection of spectral bands usable in conjunction with multispectrum scanners for qualitative and quantitative studies of algae in bodies of water.

Gramms, L. C.↗
NASA NTRS1979

Identification and area estimation of agricultural crops by computer classification of Landsat MSS data

Landsat Multispectral Scanner (MSS) data covering a three-county area in northern Illinois were classified using computer-aided techniques as corn, soybeans, or 'other.' Recognition of test fields was 80% accurate. County estimates of the area of corn and soybeans agreed closely with those made by the USDA. Results of the use of a priori information in classification, techniques to produce unbiased area estimates, and the use of temporal and spatial features for classification are discussed. The extendability, variability, and size of training sets, wavelength band selection, and spectral characteristics of crops were also investigated.

Bauer, M. E.↗
NASA NTRS1981

Technologies for the multispectral mapping of earth resources

The application of solid-state detector array imaging to the remote sensing of the earth as a follow-on to currently planned Landsat missions provides the opportunity to achieve significantly increased performance. First-order advantages to be anticipated are higher sensitivity resulting in greater radiometric accuracies and improved geometric fidelity. The Multispectral Mapper design concept is responsive to a broad range of user needs by incorporating in-flight selection of spectral bands, instantaneous fields of view, and swath width. This versatility is achieved by the use of an imaging spectrometer which permits both spatial and spectral sampling in the image plane using area array detectors. Other improvements over the current Landsat multispectral scanner and Thematic Mapper include higher spatial resolution and inherently precise registration of the spectral bands. The key technologies required in order to realize these improvements include short-wavelength infrared detectors, wide field of view, broad spectral coverage optics, focal plane cooling, and high-speed onboard signal processing. Significant development activities will be required if an advanced remote sensing capability is to be implemented.

Wellman, J. B.↗
NASA NTRS1983

Contribution of LANDSAT-4 thematic mapper data to geologic exploration

The increased number of carefully selected narrow spectral bands and the increased spatial resolution of thematic mapper data over previously available satellite data contribute greatly to geologic exploration, both by providing spectral information that permits lithologic differentiation and recognition of alteration and spatial information that reveals structure. As vegetation and soil cover increase, the value of spectral components of TM data decreases relative to the value of the spatial component of the data. However, even in vegetated areas, the greater spectral breadth and discrimination of TM data permits improved recognition and mapping of spatial elements of the terrain. As our understanding of the spectral manifestations of the responses of soils and vegetation to unusual chemical environments increases, the value of spectral components of TM data to exploration will greatly improve in covered areas.

Everett, J. R.↗
NASA NTRS2000

Mineralogical and Geochemical Analyses of Antarctic Lake Sediments: A Reflectance and Moessbauer Spectroscopy Study with Applications for Remote Sensing on Mars

Lakebottom sediments from the Dry Valleys region of Antarctica have been analyzed here in order to study the influence of water chemistry on the mineralogy and geochemistry of these sediments, as well as to evaluate techniques for remote spectral identification of potential biomarker minerals on Mars. Lakes from the Dry Valleys region of Antarctica have been investigated as possible analogs for extinct lake environments on early Mars. Sediment cores were collected in the present study from perennially ice-covered Lake Hoare in the Taylor Valley. These sediments were taken from a core in an oxic region of the lake and another core in an anoxic zone. Differences between the two cores were observed in the sediment color, Fe(II)/Fe(III) ratio, the presence of pyrite, the abundance of Fe, S and some trace elements, and the C, N and S isotope fractionation patterns. The results of visible-infrared reflectance spectroscopy (0.3-25 microns) Mossbauer spectroscopy (77 and 4 K) and X-ray diffraction are combined to determine the mineralogy and composition of these samples. The sediments are dominated by plagioclase, K-feldspar, quartz and pyroxene. Algal mats grow on the bottom of the lake and organic material has been found throughout the cores. Calcite is abundant in some layers of the aerobic core (shallow region) and pyrite is abundant in some layers of the anaerobic core (deep region). Analysis of the spectroscopic features due to organics and carbonates with respect to the abundance of organic C and carbonate contents was performed in order to select optimal spectral bands for remote identification of these components in planetary regoliths. Carbonate bands near 4 and 6.8 microns (approx.2500 and 1500/cm) were detected for carbonate abundances as low as 0.1 wt.% CO2. Organic features at 3.38, 3.42 and 3.51 microns (2960, 2925 and 2850/cm) were detected for organic C abundances as low as 0.06 wt.% C. The d13C trends show a more complex organic history for the anaerobic sediments than for the aerobic sediments. The biogenic pyrite found in the anaerobic core is associated with lighter d34S values and high organic C levels and could be used as a biomarker mineral for paleolakes on Mars.

Froeschl, Heinz↗
NASA NTRS2004

Spatially modulated interferometer and beam shearing device therefor

A spatially modulated interferometer incorporates a beam shearing system having a plurality of reflective surfaces defining separate light paths of equal optical path length for two separate output beams. The reflective surfaces are arranged such that when the two beams emerge from the beam shearing system they contain more than 50 percent of the photon flux within the selected spectral pass band. In one embodiment, the reflective surfaces are located on a number of prism elements combined to form a beam shearing prism structure. The interferometer utilizing the beam sharing system of the invention includes fore-optics for collecting light and focusing it into a beam to be sheared, and a detector located at an exit pupil of the device. In a preferred embodiment, the interferometer has no moving parts.

Reininger, Francis M.↗
NASA NTRS1976

Evaluation of transmittance of selected infrared bands

Computer programs were developed for evaluating homogeneous path transmittance with line-by-line and quasi-random band model formulations. Spectral transmittances for some selected bands of different gases (CO, N2O, CO2, H2O) were obtained using these programs. Results of theoretical computations are compared with available experimental measurements. Significant errors are observed in the results obtained from a quasi-random band model formulation, indicating that it is inadequate to meet the accuracy requirements for atmospheric work.

Gupta, S. K.↗
NASA NTRS1990

MODIS-N - Moderate Resolution Imaging Spectrometer-Nadir

The Moderate Resolution Imaging Spectrometer-Nadir (MODIS-N) for the Earth Observing System (EOS) is intended to provide daily global surveys for the atmosphere, the oceans, and the land. To achieve this capability, MODIS-N requires an at-least 2300-km swath width, and provides geometric-instantaneous-fields-of-view (GIFOVs) that are either 856 m, 428 m, or 214 m in size with reference to a 705 km satellite altitude. The 214 m GIFOV may or may not be used depending on total data rate impact assessments traded with science needs. To achieve the data for the multiplicity of science investigations MODIS-N provides nominally 36 spectral bands that are selected for specific locations and bandpasses in the spectral range from the visible to the long wave infrared. Another driver of this instrument combination is the need for long term spectral and radiometric calibration stability. Specific calibration capabilities are to be built into MODIS-N to achieve calibration knowledge over a 5 year operational life.

Weber, Richard R.↗
NASA NTRS2009

Progressive Band Selection

Progressive band selection (PBS) reduces spectral redundancy without significant loss of information, thereby reducing hyperspectral image data volume and processing time. Used onboard a spacecraft, it can also reduce image downlink time. PBS prioritizes an image's spectral bands according to priority scores that measure their significance to a specific application. Then it uses one of three methods to select an appropriate number of the most useful bands. Key challenges for PBS include selecting an appropriate criterion to generate band priority scores, and determining how many bands should be retained in the reduced image. The image's Virtual Dimensionality (VD), once computed, is a reasonable estimate of the latter. We describe the major design details of PBS and test PBS in a land classification experiment.

Fisher, Kevin↗
DOE OSTI2025

Full Device Evaluation of Metal Halide Perovskite Solar Cells in Low Earth Orbit Aboard the International Space Station

This study investigates how sustained low Earth orbit (LEO) exposure affects metal halide perovskite (MHP) thin films and perovskite solar cells (PSCs). It examines samples deployed on the Materials International Space Station Experiment (MISSE) 15 and 16 missions. Five methylammonium lead iodide (MAPI) thin films are deployed on MISSE-16, each with distinct UV filters to selectively attenuate AM0 spectral bands. While post-flight optical analysis reveals that the least UV-exposed film exhibits the highest emission and lowest non-radiative recombination rate, no clear correlation is observed among the rest, and all MAPI films maintained excellent integrity throughout the mission. MISSE-15 deployed eight PSCs with diverse structures, MHP compositions, and contact materials. Post-flight analysis reveals stable, highly emissive MHPs, but damaged contacts due to ion migration, which caused loss of electrical response. The MISSE missions demonstrate MHPs' suitability for space applications, while highlighting the need for improved interfacial layers and contact materials to enhance charge carrier mobility, prevent ion migration, and improve charge carrier extraction efficiency.

14 SOLAR ENERGY↗
NASA NTRS1976

Documentation of procedures for textural/spatial pattern recognition techniques

A C-130 aircraft was flown over the Sam Houston National Forest on March 21, 1973 at 10,000 feet altitude to collect multispectral scanner (MSS) data. Existing textural and spatial automatic processing techniques were used to classify the MSS imagery into specified timber categories. Several classification experiments were performed on this data using features selected from the spectral bands and a textural transform band. The results indicate that (1) spatial post-processing a classified image can cut the classification error to 1/2 or 1/3 of its initial value, (2) spatial post-processing the classified image using combined spectral and textural features produces a resulting image with less error than post-processing a classified image using only spectral features and (3) classification without spatial post processing using the combined spectral textural features tends to produce about the same error rate as a classification without spatial post processing using only spectral features.

Haralick, R. M.↗
NASA NTRS1976

A very-long-baseline interferometer system for geodetic applications

A very-long-baseline interferometer system was designed and built for geodetic applications. Each interferometer terminal records a 360-kHz spectral band of noise from a compact extragalactic radio source. The center frequency of the spectral band can be selected to sample sequentially bands covering a much wider frequency range to obtain subnanosecond accuracy in group-delay measurements. A tunnel-diode pulse generator is used to calibrate the delays in the receiver. The necessary sets of algorithms and computer programs have been developed to analyze the data and have allowed the system to be employed to make accurate determinations of vector baselines, radio-source positions, polar motion, and universal time.

Whitney, A. R.↗
NASA NTRS1991

Regional exploration in desert terrains - A guide to the use of Landsat Thematic Mapper imagery

This paper provides a guide for the acquisition, processing, and interpretation of Landsat Thematic Mapper (TM) imagery of desert terrains for use in regional exploration. Sun angle considerations, data quality cautions, noise suppression routines, band selections, data calibration, spectral enhancements, perceptual considerations of displays, and general interpretation guidelines are all discussed as components of an image-information extraction procedure.

Crippen, Robert E.↗
NASA NTRS1980

Remote sensing of surface mines - A comparative study of sensor systems

The application of remote sensing to the inventory of coal surface mines and to the monitoring of mine reclamation in the eastern United States was investigated. Data were acquired during spring and autumn by several sensor systems over study areas located within the bituminous coal fields of Pennsylvania. Data sources were the Landsat MSS, an airborne multispectral scanner (Daedalus DS-1260), the airborne Thematic Mapper Simulator, and high-altitude color and color infrared aerial photography. A comparison of the data sets was conducted by a quantitative assessment of area measurement accuracy. Landsat data were found most suitable for a synoptic inventory of mines on a regional basis. High-altitude aerial photography was considered the best source of the detailed information required for reclamation monitoring. Nine channels of data from the airborne scanner were evaluated to select the most useful spectral bands for discriminating among the land cover types associated with surface mines. Four bands were selected in the following order by a stepwise linear discriminant procedure: 0.60-0.65 micron, 0.92-1.10 microns, 0.80-0.89 micron, and 8-14 microns. The data corresponding to these four bands were used for the thematic mapping of land cover.

Irons, J. R.↗