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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 541 records · Page 30
All sourcesNASA NTRSDOE OSTI
NASA NTRS1983

An Empirical Bayes Approach to Spatial Analysis

Multi-channel LANDSAT data are collected in several passes over agricultural areas during the growing season. How empirical Bayes modeling can be used to develop crop identification and discrimination techniques that account for spatial correlation in such data is considered. The approach models the unobservable parameters and the data separately, hoping to take advantage of the fact that the bulk of spatial correlation lies in the parameter process. The problem is then framed in terms of estimating posterior probabilities of crop types for each spatial area. Some empirical Bayes spatial estimation methods are used to estimate the logits of these probabilities.

Morris, C. N.↗
NASA NTRS1983

Self-correcting electronically scanned pressure sensor

A multiple channel high data rate pressure sensing device is disclosed for use in wind tunnels, spacecraft, airborne, process control, automotive, etc., pressure measurements. Data rates in excess of 100,000 measurements per second are offered with inaccuracies from temperature shifts less than 0.25% (nominal) of full scale over a temperature span of 55 C. The device consists of thirty-two solid state sensors, signal multiplexing electronics to electronically address each sensor, and digital electronic circuitry to automatically correct the inherent thermal shift errors of the pressure sensors and their associated electronics.

Gross, C.↗
NASA NTRS1982

Grapevine canopy reflectance and yield

Field spectroradiometric and airborne multispectral scanner data were applied in a study of Concord grapevines. Spectroradiometric measurements of 18 experimental vines were collected on three dates during one growing season. Spectral reflectance, determined at 30 intervals from 0.4 to 1.1 microns, was correlated with vine yield, pruning weight, clusters/vine, and nitrogen input. One date of airborne multispectral scanner data (11 channels) was collected over commercial vineyards, and the average radiance values for eight vineyard sections were correlated with the corresponding average yields. Although some correlations were significant, they were inadequate for developing a reliable yield prediction model.

Minden, K. A.↗
NASA NTRS1982

Space station communications and tracking equipment management/control system

Design details of a communications and tracking (C and T) local area network and the distribution system requirements for the prospective space station are described. The hardware will be constructed of LRUs, including those for baseband, RF, and antenna subsystems. It is noted that the C and T equipment must be routed throughout the station to accommodate growth of the station. Configurations of the C and T modules will therefore be dependent on the function of the space station module where they are located. A block diagram is provided of a sample C and T hardware distribution configuration. A topology and protocol will be needed to accommodate new terminals, wide bandwidths, bidirectional message transmission, and distributed functioning. Consideration will be given to collisions occurring in the data transmission channels.

Kapell, M. H.↗
NASA NTRS1985

Short meridional scale anomalies in the lower stratosphere and upper troposphere

Consequences of the discovery of short-meridional scale anomalies (SMSAs) in the lower stratospheric temperature field in the analyses of Microwave Sounding Unit channel 4 data are examined. The time scales of these features, their presence in the u-wind, v-wind, and geopotential, and the heat and momentum fluxes resulting from the SMSAs are investigated. The SMSAs are not regularly propagating features. Latitudinal movement occurs in both northern and southern directions. Both eastward movement and stationarity are observed in the zonal direction. In episodes, SMSAs require a few days to grow, persist from a few days to two weeks, and then decay over a few days. Heat fluxes are small. It is suggested that the SMSAs are possibly caused by secondary effects of baroclinic disturbances.

Newman, P. A.↗
NASA NTRS1985

Multipolarization SAR data for surface feature delineation

This paper presents the techniques and the utility of multipolarization Synthetic Aperture Radar (SAR) data for surface feature delineation. Three channels of ratioed data (VV/HH, VH/HH, and VH/VV) are generated from the HH, VV, and VH polarization data (V = vertical, H = horizontal). The technique assumes redundancy of the VH and HV polarization and only VH polarization is used. The ratioed data are linearly stretched to yield a digital number within a range of 0 to 255. Based on the separability measure for two-class delineation, it was found that (1) the ratioed data resulted in a better delineation of surface features with high like (HH or VV) polarization digital number, and (2) the use of ratioed data provided further information not available from the original three-polarization data. The results suggest an advantage in using the ratioed data and the original three-polarization data for surface feature delineation.

Wu, S. T.↗
NASA NTRS1986

Angular dependence of reflectance of land cover surfaces

Preliminary results are discussed from an investigation into the effects of the solar zenith angle on the surface reflectances of cloud types being categorized in the International Satellite Cloud Climatology Project. The analysis is based on AVHRR channel one data at 0.6 micron over the period July 1983-July 1984. Subsatellite scenes of eight geographically separated targets distinguished by their predominant vegetation type were examined pixel-by-pixel. Attempts were made to discover any spatial variability index in each pixel to classify pixels representing clouds by the recorded brightness temperature.

Brest, C. L.↗
NASA NTRS1988

Dehydration in the lower Antarctic stratosphere in late winter and spring

The history of minimum temperatures at 50 and 70 mb is examined from NMC, UK Met 0 and ECMWF analyses. MSU channel 24 data are similarly inspected. South Pole sonde data are used to calculate saturation humidity mixing ratio as a function of altitude and time throughout 1987. Saturation with respect to ice could be maintained for water mixing ratios of 3.5 ppmv for a period of about 80 days from mid-June to mid-September. Dehydration to mixing ratios of 1 ppmv or less was possible sporadically. Data from the ER-2 flights between 53 S and 72 S are used in conjunction with particle size measurements and air parcel trajectories to demonstrate the dehydration occurring over Antarctica. Water mixing ratios at the latitude of Punta Arenas (53 S), in conjunction with tracer measurements and trajectory analysis, show that at potential temperatures from about 325 to 400 K, the dryness (less than 3 ppmv) had its origin over Antarctica rather than in the tropics. Water mixing ratios within the Antarctic vortex varied from 1.5 to 3.8 ppmv, with a strong isentropic gradient being evident in the region of high potential vorticity gradients.

Kelly, K. K.↗
NASA NTRS1989

Lidar validation of VAS cirrus cloud height determinations

The determination of cirrus cloud pressure altitude and IR attenuation using CO2 channel radiometric data from the VISSR (Visible and Infrared Spin Scan Radiometer) Atmospheric Sounder (VAS) on board the GOES geostationary satellite is discussed. The independent ground-based determination of cirrus cloud altitude, thickness, and optical properties obtained with the High Spectral Resolution Lidar (HSRL) is described. HSRL cirrus cloud measurements are compared to VAS CO2 cloud top height retrievals generated for the First International Satellite Cloud Climatology Project Regional Experiment cirrus intensive Field Observations, held in Wisconsin in October and November of 1986.

Grund, Christian J.↗
NASA NTRS1989

Dehydration in the lower Antarctic stratosphere during late winter and early spring, 1987

The history of minimum temperatures at 50 and 70 mb is examined from NMC, UK Met O and ECMWF analyses. MSU channel 24 data are similarly inspected. South Pole sonde data are used to calculate saturation humidity mixing ratio as a function of altitude and time throughout 1987. Saturation with respect to ice could be maintained for water mixing ratios of 3.5 ppmv for a period of about 80 days from mid-June to mid-September. Dehydration to mixing ratios of 1 ppmv or less was possible sporadically. Data from the ER-2 flights between 53 S and 72 S are used in conjunction with particle size measurements and air parcel trajectories to demonstrate the dehydration occurring over Antarctica. Water mixing ratios at the latitude of Punta Arens (53 S), in conjunction with tracer measurements and trajectory analysis, show that at potential temperatures from about 325 to 400 K, the dryness (less than 3 ppmv) had its origin over Antarctica rather than in the tropics. Water mixing ratios within the Antarctic vortex varied from 1.5 to 3.8 ppmv, with a strong isentropic gradient being evident in the region of high potential vorticity gradients.

Kelly, K. K.↗
NASA NTRS1990

Mineral mapping at Cuprite, Nevada with a 63-channel imaging spectrometer

Geophysical and Environmental Research Imaging Spectrometer (GERIS) 63-channel scanner data covering the spectral region 0.4 to 2.5 microns were analyzed for the Cuprite mining district, Esmeralda and Nye Counties, Nevada. Individual and spatially averaged spectra extracted from the GERIS data were used to identify the minerals alunite, kaolinite, buddingtonite, and hematite by their spectral characteristics. The images were classified in the spectral domain to produce color-coded image maps of mineral distribution that clearly show the zoned nature of the hydrothermal system. Comparison of the thematic mineral maps with existing geologic and alteration maps demonstrates the utility of imaging spectrometers for producing detailed maps for mineral exploration.

Kruse, F. A.↗
NASA NTRS1989

NASA/GSFC program in direct detection optical communications for intersatellite links

NASA-Goddard has undertaken the development of direct-detection optical communications for space applications at the Gbps data rate channel capability level. The primary challenges to optical communications designers lie in the development of reliable optical power sources, as well as of high performance pointing/acquisition/tracking systems required by the narrow widths of the transmitted optical beams. GaAlAs diodes and their arrays are currently the most attractive technology for optical transmitters; pioneering work has also been conducted on dichroic and grating techniques for combining the power of several laser diodes. Attention is given to the performance obtained for an optical link acquisition and submicroradian tracking/pointing system.

Fitzmaurice, M.↗
NASA NTRS1991

Low Reynolds number two-equation modeling of turbulent flows

A k-epsilon model that accounts for viscous and wall effects is presented. The proposed formulation does not contain the local wall distance thereby making very simple the application to complex geometries. The formulation is based on an existing k-epsilon model that proved to fit very well with the results of direct numerical simulation. The new form is compared with nine different two-equation models and with direct numerical simulation for a fully developed channel flow at Re = 3300. The simple flow configuration allows a comparison free from numerical inaccuracies. The computed results prove that few of the considered forms exhibit a satisfactory agreement with the channel flow data. The model shows an improvement with respect to the existing formulations.

Michelassi, V.↗
NASA NTRS1990

Mapping sea ice leads with a coupled numeric/symbolic system

A method is presented which facilitates the detection and delineation of leads with single-channel Landsat data by coupling numeric and symbolic procedures. The procedure consists of three steps: (1) using the dynamic threshold method, an image is mapped to a lead/no lead binary image; (2) the likelihood of fragments to be real leads is examined with a set of numeric rules; and (3) pairs of objects are examined geometrically and merged where possible. The processing ends when all fragments are merged and statistical characteristics are determined, and a map of valid lead objects are left which summarizes useful physical in the lead complexes. Direct implementation of domain knowledge and rapid prototyping are two benefits of the rule-based system. The approach is found to be more successfully applied to mid- and high-level processing, and the system can retrieve statistics about sea-ice leads as well as detect the leads.

Key, J.↗
NASA NTRS1991

Estimation of emittances and surface temperatures from AVHRR data

An approach to the estimation of surface temperatures and emissivities using AVHRR (Advanced Very High Resolution Radiometer) data acquired near noon is presented. Thermal data in channels 3, 4, and 5 were used to estimate the reflective component in 3. For three water bodies in Oregon the average emittances found for channels 3 and 4 were 0.979 and 0.991, respectively. Also studied were agricultural sites and forests, comprising both primary (PF) and secondary (SF) types. For the agricultural sites, the average emittances were 0.919 and 0.943 for channels 3 and 4. For the PF and SF the results were 0.976 and 0.983 for channel 3 and 0.988 and 0.995 for channel 4.

Schutt, John B.↗
NASA NTRS1992

Status of the NASA SETI Sky Survey microwave observing project

The Sky Survey observing program is one of two complementary strategies that NASA plans to use in its microwave Search for Extraterrestrial Intelligence (SETI). The primary objective of the Sky Survey is to search the entire sky over the frequency range 1000-10,000 MHz for evidence of narrow band signals of extraterrestrial, intelligent origin. Spectrum analyzers with upwards of 10 million channels and data rates in excess of 10 gigabits per second are required to complete the survey in less than 7 years. To lay the foundation for the operational SETI Sky Survey, a prototype system has been built to test and refine real time signal detection algorithms, to test scan strategies and observatory control functions, and to test algorithms designed to reject radio frequency interference. This paper presents a high level description of the prototype hardware and reports on the preparations to deploy the system to the 34-m antenna at the research and development station of NASA's Deep Space Communication Complex, Goldstone, California.

Klein, M. J.↗
NASA NTRS1992

In-flight detection of flow separation, stagnation, and transition

Flight tests were conducted to demonstrate the feasibility of simultaneous determination of: (1) boundary-layer instability and transition characteristics; (2) flow separation region; and (3) the location of the leading-edge stagnation point. Surface mounted, multi-element, micro-thin, hot-film sensors were used in conjunction with a bank of constant-temperature anemometers and a PC-based 8-channel simultaneous data acquisition system. Conventional techniques were used to determine the boundary-layer instability and transition characteristics while the flow separation and the stagnation points were determined through the presence of phase reversal signatures.

Mangalam, S. M.↗
NASA NTRS1993

The new face of Venus

The Magellan data on the Venus landscape which revealed volcanoes, shining mountains, relaxing plateaus, and craters on the surface of about 500 C, with an atmospheric pressure 90 times that of earth, are discussed. Venus is considered to be a planet that is both incredibly similar and dissimilar to earth. Venus might not exhibit plate tectonism but it might be dominated by catastrophes. The greenhouse around Venus has operated for at least the last 500 million years. The Magellan data revealed channels extending for thousands of kilometers, beautiful outflows surrounding impact craters, and odd volcanic constructs like the steep-sided domes.

Stofan, Ellen R.↗