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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 847 records · Page 47
All sourcesNASA NTRSDOE OSTI
NASA NTRS1973

Results of the Apollo 15 and 16 X-ray experiment

Except for some minor modifications the Apollo 16 X-ray fluorescence experiment was similar to that flown aboard Apollo 15. The Apollo 16 provided data for a number of features not previously covered such as Mare Cognitum, Mare Nubium, Ptolemaeus, Descartes, Mendeleev, and other areas. Many data points were obtained by the X-ray experiments, so that comparisons could be drawn between Apollo 15 and 16 flights. The agreement was generally within about 10%. Al/Si concentration ratios ranged from 0.38% in Mare Cognitum to 0.67% in the Descartes area highlands. A comparison of the Apollo 16 data Al/Si values with optical albedo values along the ground tracks showed the same positive correlation as in the Apollo 15 flight. A reexamination of the detector and collimator geometries showed that the spatial resolution was better by almost a factor of two than the initial estimates.

Adler, I.↗
NASA NTRS1983

Geologic mapping of the Bauru Group in Sao Paulo state by LANDSAT images

The occurrence of the Bauru Group in Sao Paulo State was studied, with emphasis on the western plateau. Regional geological mapping was carried out on a 1:250.000 scale with the help of MSS/LANDSAT images. The visual interpretation of images consisted basically of identifying different spectral characteristics of the geological units using channels 5 and 7. Complementary studies were made for treatment of data with an Interative Image (I-100) analyser in order to facilitate the extraction of information, particularly for areas where visual interpretation proved to be difficult. Regional characteristics provided by MSS/LANDSAT images, coupled with lithostratigraphic studies carried out in the areas of occurrence of Bauru Group sediments, enabled the homogenization of criteria for the subdivision of this group. A spatial distribution of the mapped units was obtained for the entire State of Sao Paulo and results were correlated with proposed stratigraphic divisions.

Parada, N. D. J.↗
NASA NTRS1983

Study on spectral/radiometric characteristics of the Thematic Mapper for land use applications

Previous characterization of scan-related low-frequency noise was extended and refined through detailed analysis of shutter calibration data on CCT-ADDS tapes and reflective-band data from nighttime acquisitions. A recommended correction procedure was identified that uses calibration shutter data both as a diagnostic and to obtain correction values. Through comparison of coincident TM and MSS data, illustrations of the added information content of TM data for agricultural applications were developed. The capability of improved spatial resolution to better define boundaries and to resolve spatial details is shown. Spectral analysis of tasseled-cap transformations of TM and MSS data shows high correlation between greenness features, greater signal range for TM, and indications that a subset of TM bands could accurately simulate MSS data, if required.

Malila, W. A.↗
NASA NTRS1983

Solar wind deceleration and MHD turbulence in the earth's foreshock region - ISEE 1 and 2 and IMP 8 observations

The interaction of the solar wind with ions backstreaming from the earth's bow shock is investigated using plasma and magnetic field measurements on ISEE 1 and 2 and IMP 8 at widely separated positions in the earth's foreshock. This technique separates temporal and spatial variations within the foreshock. It is found that the solar wind acceleration associated with backstreaming ions is correlated with the amplitude of the MHD turbulence, and that the largest decelerations are seen close to the bow shock. The density of the backstreaming ion beam is strongly correlated with distance from the shock, and decreases by about a factor of three in a distance of about 3R(e).

Bonifazi, C.↗
NASA NTRS1990

Venturi Air-Jet Vacuum Ejector For Sampling Air

Venturi air-jet vacuum ejector pump light in weight, requires no electrical power, does not contribute heat to aircraft, and provides high pumping speeds at moderate suctions. High-pressure motive gas required for this type of pump bled from compressor of aircraft engine with negligible effect on performance of engine. Used as source of vacuum for differential-absorption CO-measurement (DACOM), modified to achieve in situ measurements of CO at frequency response of 10 Hz. Provides improvement in spatial resolution and potentially leads to capability to measure turbulent flux of CO by use of eddy-correlation technique.

Hill, Gerald F.↗
NASA NTRS1994

A high resolution atlas of the galactic plane at 12 microns and 25 microns

High resolution images of the 12 micron and 25 micron IRAS survey data from each HCON crossing the Galactic Plane are being created for those regions that the original IRAS processing labeled as confused. This encompasses the area within 100 deg longitude of the Galactic Center and within 3 deg to 10 deg of the Plane. The procedures used to create the images preserve the spatial resolution inherent in the IRAS instrument. The images are separated into diffuse and point source components and candidate sources are extracted from the point source image after non-linear spatial sharpening. Fluxes are estimated by convolving the candidate sources with the point response function and cross-correlating with the original point source image. A source is considered real if it is seen on at least two HCON's with a rather generous flux match but a stringent position criterion. A number of fields spanning a range of source densities from low to high have been examined. Initial analysis indicates that the imaging and extraction works quite well up to a source density of about 100 sources per square degree or down to roughly 0.8 Janskys.

Price, Stephan D.↗
NASA NTRS1995

Preliminary results of the analysis of CaII K spectroheliograms

The preliminary results of the photometry of CaII K spectroheliograms are presented. From the spectrograms for 1992, plages, the magnetic network, intranetwork elements and the chromospheric background were separated using the histogram method. The intensity and area of these separated features, as well as the full disk intensity, were derived. The spatial K index was compared to the spectral CaII K index derived from line profiles. It was found that the spatial K index and intensity of plages, the network elements and the intranetwork and background regions were highly correlated with the MgII h and k c/w ratio.

Kariyappa, R.↗
NASA NTRS1996

The Three-Dimensional Spatial Structure of Cirrus Clouds Determined from Lidar Satellite Observations

Simultaneous imagery from the University of Wisconsin Volume Imaging Lidar (VIL) and meteorological satellites were used to quantify the spatial structure of cirrus clouds with 60 m resolution. This data was used to determine the spatial distributions of cloud base altitude, cloud top altitude, and mid-cloud altitude. Two dimensional auto-correlation functions describing the mean shape of cirrus clouds were computed. Because cirrus clouds seldom have distinct edges, these correlation functions are derived as a function of a threshold value which defines the cloud edge.

Eloranta, E. W.↗
NASA NTRS2000

Microwave Sensing of Ocean Winds Including the Use of SAR Imagery

This paper presents aircraft measurements of near-surface atmospheric boundary layer wind roll signatures and radar-derived sea surface roughness. These data are completely coincident in space and time and this unique feature supports attempts to definitively link SAR backscatter signatures to boundary layer roll impacts. The open-ocean data were collected at an altitude of 20 m from NOAA's Long-EZ aircraft using its turbulence probe and down-looking Ka-band radar scatterometer. Several flight legs of 20-30 km were flown with a heading across the wind direction, which is also roughly perpendicular to the roll vortices. We find remarkable correlation between measured modulations in the along-wind component of wind speed and radar backscatter for the spatial scale of 1 to 1.5 km. Close agreement between normalized modulation amplitudes suggests the radar-inferred surface slope variance is changing linearly with wind speed. These data were collected within 30 minutes of a RADARSAT SAR overpass where apparent boundary layer impacts of the same orientation and spatial dimension are prevalent in the SAR backscatter image. Quantitative comparison between modulations in the aircraft and satellite radar data will be discussed.

Vandemark, Douglas↗
NASA NTRS2000

Measured Correlation Between Roll-Vortex Signatures and Radar-Inferred Sea Surface Roughness

This paper presents aircraft measurements of near-surface atmospheric boundary layer roll signatures and radar-derived sea surface roughness. These data are completely coincident in space and time and this unique feature supports attempts to definitively link SAR backscatter signatures to boundary layer roll impacts. The open-ocean data were collected at an altitude of 20 in from NOAA's Long-EZ aircraft using its turbulence probe and down-looking Ka-band radar scatterometer, Several flight legs of 20-30 km were flown with a heading across the wind direction, which is also roughly perpendicular to the roll vortices. We find remarkable correlation between measured modulations in the along-wind component of wind speed and radar backscatter for the spatial scale of I to 1.5 kin. Close agreement between normalized modulation amplitudes suggests the radar-inferred surface slope variance is changing linearly with wind speed. These data were collected within 30 minutes of a RADARSAT SAR overpass where apparent boundary layer impacts of the same orientation and spatial dimension are prevalent in the SAR backscatter image. Quantitative comparison between modulations in the aircraft and satellite radar data will be discussed.

Vandemark, Douglas↗
NASA NTRS1983

The correlation of coronal mass ejections with energetic flare proton events

Proton events of energies of at least 4 MeV presumed due to solar flares are compared with coronal mass ejections (CMEs) observed with an orbiting coronagraph. H alpha flares are associated with 27 of the 50 flare proton events of the study. Each of these 27 flares is then associated temporally and spatially with a CME, confirming the earlier conclusion, based on Skylab data, that a CME may be a necessary condition for a flare proton event. Peak 4-22 MeV proton fluxes correlate with both the speeds and the angular sizes of the associated CMEs. CMEs of larger angular sizes are more likely to be loops or fans rather than jets or spikes and are more likely to intersect the ecliptic.

Kahler, S. W.↗
NASA NTRS2019

Multi-Channel Correlator Array-Fed Microwave Radiometer

New antenna feed technology is needed for microwave radiometers as aperture sizes continue to increase. Capability for contiguous coverage and spatial Nyquist sampling can be achieved using a multi-beam array-fed reflector architecture adapted from radio astronomy. In this ACT (Advanced Component Technology), a wideband feed array for use in a multi-channel (X-W bands) scanning microwave radiometer is in development. The team, including array provider Nuvotronics Inc., is also developing a laboratory instrument to demonstrate the performance of the array-fed architecture at 36.5 gigahertz using an 80-centimeter projected aperture. The feed array is an 11-element line array based on a microfabricated 8-40 gigahertz feed. Multiple beams are generated by exciting overlapping groups of elements with each group shifted by one element spacing within the array. The modeled antenna patterns reveal six beams with 0.8-degree beamwidth and 0.3-degree spacing. This configuration is also a 1:26 electromagnetic scale model of a 1.41 gigahertz radiometer with a 21-meter aperture. The array-fed architecture for microwave radiometers has the potential to solve the developing need for high-spatial resolution, large aperture instruments. The objective relevancy scenario is a 6-meter aperture X-W band scanning radiometer purposed for high-resolution all-weather imaging of Earth's atmosphere and land, ice and ocean surfaces.

Microwave Radiometer↗
NASA NTRS1978

A Fourier approach to cloud motion estimation

A Fourier phase-difference technique for cloud motion estimation from pairs of pictures is described, and results obtained using this technique are compared with the results of a Fourier-domain cross-correlation scheme. The phase-difference technique makes use of the phase of the cross-spectral density and allows motion estimates to be made for individual spatial frequencies, which are related to cloud pattern dimensions. When objects being tracked do not change their shape, size, and orientation to more than a limited degree, both techniques are effective. The phase difference technique is relatively sensitive to the presence of mixtures of motions, changes in cloud shape, and edge effects; in these circumstances, the cross-correlation scheme is preferable. It is suggested that the Fourier transform phase difference estimation methods can be applied in problems such as landmark matching.

Arking, A.↗
NASA NTRS2011

Remote Sensing the Vertical Profile of Cloud Droplet Effective Radius, Thermodynamic Phase, and Temperature

Cloud-aerosol interaction is a key issue in the climate system, affecting the water cycle, the weather, and the total energy balance including the spatial and temporal distribution of latent heat release. Information on the vertical distribution of cloud droplet microphysics and thermodynamic phase as a function of temperature or height, can be correlated with details of the aerosol field to provide insight on how these particles are affecting cloud properties and their consequences to cloud lifetime, precipitation, water cycle, and general energy balance. Unfortunately, today's experimental methods still lack the observational tools that can characterize the true evolution of the cloud microphysical, spatial and temporal structure in the cloud droplet scale, and then link these characteristics to environmental factors and properties of the cloud condensation nuclei. Here we propose and demonstrate a new experimental approach (the cloud scanner instrument) that provides the microphysical information missed in current experiments and remote sensing options. Cloud scanner measurements can be performed from aircraft, ground, or satellite by scanning the side of the clouds from the base to the top, providing us with the unique opportunity of obtaining snapshots of the cloud droplet microphysical and thermodynamic states as a function of height and brightness temperature in clouds at several development stages. The brightness temperature profile of the cloud side can be directly associated with the thermodynamic phase of the droplets to provide information on the glaciation temperature as a function of different ambient conditions, aerosol concentration, and type. An aircraft prototype of the cloud scanner was built and flew in a field campaign in Brazil.

Martins, J. V.↗
NASA NTRS2013

High Resolution Aerosol Data from MODIS Satellite for Urban Air Quality Studies

The Moderate Resolution Imaging Spectroradiometer (MODIS) provides daily global coverage, but the 10 km resolution of its aerosol optical depth (AOD) product is not suitable for studying spatial variability of aerosols in urban areas. Recently, a new Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm was developed for MODIS which provides AOD at 1 km resolution. Using MAIAC data, the relationship between MAIAC AOD and PM(sub 2.5) as measured by the 27 EPA ground monitoring stations was investigated. These results were also compared to conventional MODIS 10 km AOD retrievals (MOD04) for the same days and locations. The coefficients of determination for MOD04 and for MAIAC are R(exp 2) =0.45 and 0.50 respectively, suggested that AOD is a reasonably good proxy for PM(sub 2.5) ground concentrations. Finally, we studied the relationship between PM(sub 2.5) and AOD at the intra-urban scale (10 km) in Boston. The fine resolution results indicated spatial variability in particle concentration at a sub-10 kilometer scale. A local analysis for the Boston area showed that the AOD-PM(sub 2.5) relationship does not depend on relative humidity and air temperatures below approximately 7 C. The correlation improves for temperatures above 7 - 16 C. We found no dependence on the boundary layer height except when the former was in the range 250-500 m. Finally, we apply a mixed effects model approach to MAIAC aerosol optical depth (AOD) retrievals from MODIS to predict PM(sub 2.5) concentrations within the greater Boston area. With this approach we can control for the inherent day-to-day variability in the AOD-PM(sub 2.5) relationship, which depends on time-varying parameters such as particle optical properties, vertical and diurnal concentration profiles and ground surface reflectance. Our results show that the model-predicted PM(sub 2.5) mass concentrations are highly correlated with the actual observations (out-of-sample R(exp 2) of 0.86). Therefore, adjustment for the daily variability in the AOD-PM(sub 2.5) relationship provides a means for obtaining spatially-resolved PM(sub 2.5) concentrations.

remote sensing↗
NASA NTRS2019

Radiative Feedbacks Associated with the Madden-Julian Oscillation

Radiative kernels derived from CloudSat/CALIPSO measurements are used to diagnose radiative feedbacks induced by the Madden-Julian oscillation (MJO). Over the Indo-Pacific warm pool, positive cloud and water vapor feedbacks are coincident with the convective envelope of the MJO during its active phases, whereas the lapse rate feedback shows less obvious correlation to the propagating disturbance. During phase 2/3, when the convective envelope is over the Indian Ocean, water vapor exhibits a vertically coherent response, with the largest anomalies and strongest feedback in the middle troposphere. Though spatial structures of the feedbacks vary, the most prominent difference lies in the magnitude. Cloud changes induce the largest radiative perturbations associated with the MJO. We also find that for individual MJO events, cloud feedback and precipitation are highly correlated, suggesting that the strength of individual MJO events is largely dictated by the magnitude of cloud radiative heating of the atmosphere. In addition, stronger radiative heating due to water vapor and clouds helps the MJO survive the barrier effect of the Maritime Continent, leading to further eastward propagation. These results offer process-oriented metrics that could help to improve model simulations and predictions of the MJO in the future.

radiative feedbacks↗
NASA NTRS2012

Variance of the Quantum Dwell Time for a Nonrelativistic Particle

Munoz, Seidel, and Muga [Phys. Rev. A 79, 012108 (2009)], following an earlier proposal by Pollak and Miller [Phys. Rev. Lett. 53, 115 (1984)] in the context of a theory of a collinear chemical reaction, showed that suitable moments of a two-flux correlation function could be manipulated to yield expressions for the mean quantum dwell time and mean square quantum dwell time for a structureless particle scattering from a time-independent potential energy field between two parallel lines in a two-dimensional spacetime. The present work proposes a generalization to a charged, nonrelativistic particle scattering from a transient, spatially confined electromagnetic vector potential in four-dimensional spacetime. The geometry of the spacetime domain is that of the slab between a pair of parallel planes, in particular those defined by constant values of the third (z) spatial coordinate. The mean Nth power, N = 1, 2, 3, . . ., of the quantum dwell time in the slab is given by an expression involving an N-flux-correlation function. All these means are shown to be nonnegative. The N = 1 formula reduces to an S-matrix result published previously [G. E. Hahne, J. Phys. A 36, 7149 (2003)]; an explicit formula for N = 2, and of the variance of the dwell time in terms of the S-matrix, is worked out. A formula representing an incommensurability principle between variances of the output-minus-input flux of a pair of dynamical variables (such as the particle s time flux and others) is derived.

Hahne, Gerhard↗