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At least 973 records · Page 54
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Stellar populations in the edge-on spiral galaxy NGC 4565. I - Surface brightness and color distributions

Results are presented for photographic and photoelectric photometry of the edge-on Sb galaxy NGC 4565. Major-axis, minor-axis, and perpendicular surface brightness profiles are determined, along with color gradients parallel and perpendicular to the plane of the galaxy. It is found that the galaxy's light can be deconvolved naturally into five components: (1) a starlike nucleus located at the center of the bulge and the edge of the dust lane; (2) a thin disk containing the gas and dust, the young OB stars, and the spiral arms; (3) a thick disk that may be a locally isothermal sheet of old Population I metal-rich stars; (4) a bulge that merges smoothly into the thick disk at a radial distance of about 2.9 kpc; and (5) a corona whose light dominates the perpendicular profiles from about 2.9 to at least 8.2 kpc above the galactic plane.

Jensen, E. B.↗
NASA NTRS1982

Classification of surface units in the equatorial region of Mars based on Viking Orbiter color, albedo, and thermal data

Clusters corresponding to mappable surface units are sought in Viking Orbiter color, albedo, and thermal inertia data for the equatorial region of Mars. A principal components analysis indicated that 84% of the variance within the data for this region can be carried along two vector directions which typify the dominant trend of Martian surface materials. These dominant trends were deemphasized by stretching the data from a five-dimensional elliptical swarm into a hypersphere, through the use of principal component techniques. The decorrelated data were then plotted in a triangle diagram with red/violet, albedo and thermal inertia apices to facilitate inherent cluster discrimination. As many as eight clusters can be identified, with important mixing between them. The three major clusters consist of red and grey material extremes, along with intermediate value materials.

Arvidson, R. E.↗
NASA NTRS1983

OSTA-1/Ocean Color Experiment

Ocean Color Experiment (OCE) on the OSTA-1 mission acquired ocean images at several widely separated locations on the earth. Digital computer enhancement and band ratioing techniques were used to emphasize patterns of chlorophyll and sediment distribution in the Yellow Sea and, in one case, of bottom topography in the Great Bahama Bank. Two scenes in the Gulf of Cadiz from orbits 30 and 32 were geometrically corrected to show the movement of plankton patches. This technique enabled ocean current velocities to be deduced. A duplicate of the OCE instrument mounted on a DFVLR aircraft was flown over an area of the Atlantic Ocean off the coast of Portugal during the Shuttle mission.

Kim, H. H.↗
NASA NTRS1983

Eight-color photometry of Hyperion, Iapetus, and Phoebe

The Phoebe, Hyperion and Iapetus Saturn satellites are discussed in light of eight-color spectrophotometry, which together with observed V magnitudes and Voyager spacecraft-derived diameters yields geometric albedos of 0.07 for Iapetus, 0.06 for Phoebe, and maximum- and minimum-dimension based limits of 0.19 and 0.25 respectively for Hyperion. While both Hyperion and Iapetus have similar, very reddish spectra, it is noted that Hyperion has a much higher albedo than the dark side of Iapetus. The mean spectrum of Phoebe is much flatter, with a broad absorption feature near 1 micron. The determination of these optical differences between the surface materials of Phoebe and the dark side of Iapetus constrains the possible interaction modes between Phoebe and the other two satellites.

Tholen, D. J.↗
NASA NTRS1983

The rotation, color, phase coefficient, and diameter of 1915 Quetzalcoatl

Photoelectric observations of 1915 Quetzalcoatl on March 2, 1981 show that this asteroid has a rotational period of 4.9 + or - 0.3 hr and a lightcurve amplitude of 0.26 magnitudes. B-V and U-B colors are found to be 0.83 + or - 0.04 and 0.43 + or - 0.03, respectively, consistent with Quetzalcoatl being an S-type asteroid. Additional observations from March 31, 1981, give a linear phase coefficient of 0.033 mag/deg and a mean B(1,0) magnitude of 20.10. The resulting estimated mean diameter for Quetzalcoatl is only 0.37 km, making it one of the smallest asteroids for which physical observations have yet been made.

Binzel, R. P.↗
NASA NTRS1983

Spas color camera

The procedures to be followed in assessing the performance of the MOS color camera are defined. Aspects considered include: horizontal and vertical resolution; value of the video signal; gray scale rendition; environmental (vibration and temperature) tests; signal to noise ratios; and white balance correction.

Toffales, C.↗
NASA NTRS1983

Description of algorithms for processing Coastal Zone Color Scanner (CZCS) data

The algorithms for processing coastal zone color scanner (CZCS) data to geophysical units (pigment concentration) are described. Current public domain information for processing these data is summarized. Calibration, atmospheric correction, and bio-optical algorithms are presented. Three CZCS data processing implementations are compared.

Zion, P. M.↗
NASA NTRS1981

Development of Great Lakes algorithms for the Nimbus-G coastal zone color scanner

A series of experiments in the Great Lakes designed to evaluate the application of the Nimbus G satellite Coastal Zone Color Scanner (CZCS) were conducted. Absorption and scattering measurement data were reduced to obtain a preliminary optical model for the Great Lakes. Available optical models were used in turn to calculate subsurface reflectances for expected concentrations of chlorophyll-a pigment and suspended minerals. Multiple nonlinear regression techniques were used to derive CZCS water quality prediction equations from Great Lakes simulation data. An existing atmospheric model was combined with a water model to provide the necessary simulation data for evaluation of the preliminary CZCS algorithms. A CZCS scanner model was developed which accounts for image distorting scanner and satellite motions. This model was used in turn to generate mapping polynomials that define the transformation from the original image to one configured in a polyconic projection. Four computer programs (FORTRAN IV) for image transformation are presented.

Tanis, F. J.↗
NASA NTRS1983

The application of a color, raster scan, programmable display generator in the generation of multiple cockpit display formats

A description is provided of the application of the raster-scan, color programmable display generator (PDG) in the generation of multiple, simultaneous cockpit display formats at medium resolution, and their display on conventional R-G-B monitors and on recently developed thin film electroluminescent (TFEL) panels. The Graphics Display System of the Cockpit Systems Branch is discussed, taking into account hardware and software. Questions of system utilization are explored, giving attention to simultaneous display generation, scan standards, flat panel displays, and display enhancement software. Aspects of system performance are also examined, and an outline of future research plans is provided.

Montoya, R. J.↗
NASA NTRS1985

Vision Screening by Color Photography

Screening test developed for detecting a range of vision defects in eye, including common precursors to amblyopia. Test noninvasive, safe, and administered easily in field by operator with no medical training. Only minimal momentary cooperation of subject required: Thus, test shows promise for use with very young children. Test produces color-slide images of retinas of eyes under specially-controlled lighting conditions. Trained observer screens five children per minute.

Jayroe, R.↗
NASA NTRS1986

Algorithms for Coastal-Zone Color-Scanner Data

Software for Nimbus-7 Coastal-Zone Color-Scanner (CZCS) derived products consists of set of scientific algorithms for extracting information from CZCS-gathered data. Software uses CZCS-generated Calibrated RadianceTemperature (CRT) tape as input and outputs computer-compatible tape and film product.

Source record↗
NASA NTRS1985

Characteristic vector analysis of inflection ratio spectra: New technique for analysis of ocean color data

Characteristic vector analysis applied to inflection ratio spectra is a new approach to analyzing spectral data. The technique applied to remote data collected with the multichannel ocean color sensor (MOCS), a passive sensor, simultaneously maps the distribution of two different phytopigments, chlorophyll alpha and phycoerythrin, the ocean. The data set presented is from a series of warm core ring missions conducted during 1982. The data compare favorably with a theoretical model and with data collected on the same mission by an active sensor, the airborne oceanographic lidar (AOL).

Grew, G. W.↗
NASA NTRS1985

Theoretical and experimental analyses of the performance of two-color laser ranging systems

The statistical properties of the signals reflected from the retroreflector equipped satellites were studied. It is found that coherence interference between pulse reflections from retroreflectors of different ranges on the array platform is the primary cause of signal fluctuations. The performance of a cross-correlation technique to estimate the differential propagation time is analyzed by considering both shot noise and speckle. For the retroreflector arrays, timing performance is dominated by interference induced speckle, and the differential propagation time cannot be resolved to better than the pulse widths of the received signals. The differential timing measurements obtained over a horizontal path are analyzed. The ocean-reflected pulse measurements obtained from the airborne two-color laser altimeter experiment are presented.

Im, K. E.↗
NASA NTRS1984

Comparison of atmospheric correction algorithms for the Coastal Zone Color Scanner

Before Nimbus-7 Costal Zone Color Scanner (CZC) data can be used to distinguish between coastal water types, methods must be developed for the removal of spatial variations in aerosol path radiance. These can dominate radiance measurements made by the satellite. An assessment is presently made of the ability of four different algorithms to quantitatively remove haze effects; each was adapted for the extraction of the required scene-dependent parameters during an initial pass through the data set The CZCS correction algorithms considered are (1) the Gordon (1981, 1983) algorithm; (2) the Smith and Wilson (1981) iterative algorityhm; (3) the pseudooptical depth method; and (4) the residual component algorithm.

Tanis, F. J.↗
NASA NTRS1984

Satellite color observations of the phytoplankton distribution in the eastern Equatorial Pacific during the 1982-1983 El Nino

Images provided by the Coastal Zone Color Scanner (CZCS) onboard Nimbus-7 show the effect of the 1982-1983 El Nino upon the phytoplankton distribution around the Galapagos Islands, located on the equator. The CZCS scenes document a major redistribution of phytoplankton around the Galapagos Island during a period when sea-surface temperatures (SST) were anomalously high (28 to 29 C). The mixed layer was unusually thick for this region, and the winds and both the surface and subsurface flows changed directions. It is pointed out that the El Nino is characterized as one of the most spectacular examples of a large-amplitude, interannual response of the ocean to atmospheric forcing. The 1982-1983 El Nino is the best documented event of its kind to date, and details of its effects are discussed.

Feldman, G.↗
NASA NTRS1983

Coastal Zone Color Scanner data of rich coastal waters

Comparisons of chlorophyll concentrations and diffuse attenuation coefficients measured from ships off the central California coast were made with satellite derived estimates of the same parameters using data from the Coastal Zone Color Scanner. Very high chlorophyll concentrations were encountered in Monterey Bay. Although lower chlorophyll values acquired off Pt. Sur agreed satisfactorily with the satellite data, the high chlorophyll values departed markedly from agreement. Two possible causes for the disagreement are suggested. Comparison of diffuse attenuation coefficients from the same data sets showed closer agreement.

Wrigley, R. C.↗
NASA NTRS1985

Color measurement and discrimination

The present investigation is concerned with new results which show that for test lights with slow temporal modulations, and thus little effect on the luminance system, the vector-difference hypothesis represents an adequate characterization of discrimination data. It is pointed out that for certain experimental conditions color measurements can be successfully extended to include a difference measure which predicts the discriminability of pairs of lights. When discrimination depends principally on opponent-channel responses, discrimination thresholds can be predicted from the detection contour alone. Attention is given to discriminations with a 6-Hz Gabor function, the categorization of stimulus regions, and the nature of the visual mechanisms.

Wandell, B. A.↗
NASA NTRS1985

Direct-detection optical communication with color coded pulse position modulation signaling

The performance characteristics of a direct-detection optical communication system which is based on a laser transmitter which produces single light pulses at selected nonoverlapping optical center frequencies are discussed. The signal format, called color coded pulse position modulation (CCPPM), uses more of the total available response bandwidth characteristics of the photodetector than does ordinary PPM signaling. The advantages of CCPPM signaling are obtained at the expense of an increased optical bandwidth of the transmitted signal and a more complicated transmitter and receiver structure. When the signal format is used in conjunction with block length Reed-Solomon codes, high data rates and reliable high-speed optical communications under conditions of optimal energy efficiency are obtained.

Davidson, F.↗