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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 811 records · Page 45
All sourcesNASA NTRSDOE OSTI
NASA NTRS1977

Multispectral remote observations of hydrologic features on the North Slope of Alaska

Visible and near-infrared Landsat satellite imagery and active and passive aircraft microwave data are used to analyze some hydrologic features in Arctic Alaska. Lake studies using passive microwave imagery reveal that an increase in the microwave brightness temperature correlates with an increase in ice thickness. Synthetic Aperture Radar (SAR) imagery allows determination of lakes that are frozen to the bottom under certain conditions. Landsat imagery of lakes can be used to study summer ice cover dissipation, an indicator of lake depth. River channel morphometry and morphology studies are accomplished using SAR data with good (25 m) resolution. Landsat imagery is shown to be useful for analyzing interannual variations in the extent of river icings (aufeis). Snow depth variations are shown to be potentially discernable using passive microwave data. Finally, the present and potential applications of these remote sensing studies are discussed; these data are useful for locating potable water sources, planning construction in good locations, and for analyzing interannual climate fluctuations.

Hall, D. K.↗
NASA NTRS1979

Lunar multispectral maps - Part II of the lunar nearside

Images of the lunar surface are being obtained at several wavelengths using a silicon vidicon imaging system and ground-based telescopes. These images are recorded and processed in digital form so that quantitative information is preserved; their photometric precision has been shown to be 1% or better. Ratio images, calculated by dividing those obtained at two wavelengths (0.40/0.56 and 0.95/0.56 micron), were presented in an earlier article, and more are presented here for a total coverage of about 60% of the lunar frontside. Spatial resolution is about 2 km at the subearth point. A complex of distinct units is evident in the images. Earlier work with the reflectance spectrum of lunar materials indicates that for the most part these units are compositionally distinct. These digital images are being used by lunar geologists to interpret the history of the lunar surface.

Mccord, T. B.↗
NASA NTRS1980

Improved multispectral solar cell array

Solar-collector system projects oval-shaped color-band images onto solar cells designed to be most efficient at specific wavelength. Image size can be altered by changing width of reflecting mirror of power of lens. Image intensity is thus kept at optimum level, preventing cells from overheating.

Redmann, J. J.↗
NASA NTRS1979

Determination of noise equivalent reflectance for a multispectral scanner: A scanner sensitivity study

The methods used to calculate the sensitivity parameter noise equivalent reflectance of a remote-sensing scanner are explored, and the results are compared with values measured over calibrated test sites. Data were acquired on four occasions covering a span of 4 years and providing various atmospheric conditions. One of the calculated values was based on assumed atmospheric conditions, whereas two others were based on atmospheric models. Results indicate that the assumed atmospheric conditions provide useful answers adequate for many purposes. A nomograph was developed to indicate sensitivity variations due to geographic location, time of day, and season.

Gibbons, D. E.↗
NASA NTRS1979

On-board radiometric preprocessing for multispectral linear arrays /MLA/

A program that was undertaken to design, fabricate, and test a real-time hardwired data preprocessor is described, which applies a calibration normalization to each detector in a 576-element linear photodiode array. Various calibration problems were uncovered, such as those (1) due to system noise in recording the calibration tables, or (2) due to thermal drift and (3) due to the original quantization process. It was determined that in this experiment, noise and thermal drift led to fixed errors in the normalization of responses on the order of + or - 10 counts, out of 255 counts for many of the detectors.

Thompson, L. L.↗
NASA NTRS1979

Lunar multispectral imaging at 2.26 microns - First results

The first results of line-scan imaging of the moon at 2.26 microns and 0.56 micron are presented. Among the many features observed in the 2.26 micron/0.56 micron ratio image, fresh rock and immature soils stand out as dark (i.e., low ratio) due to their infrared absorption bands. Also notable in this image are several strikingly bright (high 2.26 micron/0.56 micron ratio) areas which are likely to contain pyroclastic, glass-related materials. Some of these bright areas correspond to dark mantling material. Others (e.g., Sulpicius Gallus, Aristarchus Plateau) are distinctly different in their overall spectral reflectance and it is suggested that these localities contain varieties of pyroclastic glass-related materials which were not sampled by Apollo 17 but which are relatively abundant elsewhere on the moon.

Davies, D. W.↗
NASA NTRS1979

A parametric model for multispectral scanners

A set of test statistics are specified and the corresponding output quantities computed by the characteristic function. Two sets of classification accuracies, one at the input and one at the output are estimated. The scanner's instantaneous field of view is changed and the variation of the output classification performance is monitored.

Mobasseri, B. G.↗
NASA NTRS1980

Trophic classification of Tennessee Valley area reservoirs derived from LANDSAT multispectral scanner data

LANDSAT MSS data from four different dates were extracted from computer tapes using a semiautomated digital data handling and analysis system. Reservoirs were extracted from the surrounding land matrix by using a Band 7 density level slice of 3; and descriptive statistics to include mean, variance, and ratio between bands for each of the four bands were calculated. Significant correlations ( 0.80) were identified between the MSS statistics and many trophic indicators from ground truth water quality data collected at 35 reservoirs in the greater Tennessee Valley region. Regression models were developed which gave significant estimates of each reservoir's trophic state as defined by its trophic state index and explained in all four LANDSAT frames at least 85 percent of the variability in the data. To illustrate the spatial variations within reservoirs as well as the relative variations between reservoirs, a table look up elliptical classification was used in conjunction with each reservoir's trophic state index to classify each reservoir on a pixel by pixel basis and produce color coded thematic representations.

Meinert, D. L.↗