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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 1,135 records · Page 63
All sourcesNASA NTRSDOE OSTI
NASA NTRS1984

The spatial evolution of t he directional wave spectrum in the Southern Ocean: Its relation to extreme waves in Agulhas Current

An experiment using the Shuttle Imaging Radar-B (SIR-B) to monitor certain properties of the ocean wave directional spectrum and to track the long swell systems as they propagate northward to encounter the Agulhas near the southeastern coast of Africa is discussed. The experiment is designed around the unique capability of SIR-B to overcome key limitations of the Seasat synthetic aperture radar data set, and to extend the existing Seasat results into new areas. Ocean wave systems will be tracked. The variable-incidence-angle capability to examine wave imaging quality will be utilized. Doppler current measurements will be attempted. An effort will be made to verify that the lower range-to-velocity ratio of SIR-B will lead to the improved response of azimuth-traveling wave systems.

Beal, R. C.↗
NASA NTRS1984

Structural investigation of the Canadian Shield by orbital radar and LANDSAT

Canadian Shield were studied by orbital radar. The primary objective of the study is scientific: to investigate and clarify the tectonic relationships of the Churchill, Superior, and Grenville Provinces, concentrating on their geologic boundaries, the Nelson and Grenvill Fronts. Theories about its origin range from in-situ regional metamorphism to tectonic sutures resulting from terrain accretion. The SIR-B investigation clarifies this problem. Secondary objectives are technique development, and include: (1) evaluation of the use of orbital radar in high altitude Precambrian terrains; (2) evaluation of look-azimuth biasing in radar and LANDSAT imagery; and (3) investigation of the synergistic use of radar, LANDSAT, and geophysical data in Precambrian studies.

Lowman, P. D., Jr.↗
NASA NTRS1984

Structural investigation of the Grenville Province by radar and other imaging and nonimaging sensors

The structural investigation of the Canadian Shield by orbital radar and LANDSAT, is outlined. The area includes parts of the central metasedimentary belt and the Ontario gneiss belt, and major structures as well-expressed topographically. The primary objective is to apply SIR-B data to the mapping of this key part of the Grenville orogen, specifically ductile fold structures and associated features, and igneous, metamorphic, and sedimentary rock (including glacial and recent sediments). Secondary objectives are to support the Canadian RADARSAT project by evaluating the baseline parameters of a Canadian imaging radar satellite planned for late in the decade. The baseline parameters include optimum incidence and azimuth angles. The experiment is to develop techniques for the use of multiple data sets.

Lowman, P. D., Jr.↗
NASA NTRS1985

Information for space radar designers: Required dynamic range vs resolution and antenna calibration using the Amazon rain forest

Calibration of the vertical pattern of the antennas for the SEASAT scatterometer was accomplished using the nearly-uniform radar return from the Amazon rain forest. A similar calibration will be attempted for the SIR-B antenna. Thick calibration is important to establish the radiometric calibration across the swath of the SIR-B, and the developed methodology will provide an important tool in the evaluation of future spaceborne imaging radars. This calibration was made by the very-wide-beam SEASAT scatterometer antennas because at 14.65 GHz the scattering coefficient of the rain forest is almost independent of angle of incidence. It is expected that the variation in scattering coefficient for the rain forest across the relatively narrow vertical beam of the SIR-B will be very small; even at L band the forest should be essentially impenetrable for radar signals, the volume scatter from the treetops will predominate as at higher frequencies. The basic research elements include: (1) examination of SIR-B images over the rain forest to establish the variability of the scattering coefficient at finer resolutions than that of the SEASAT scatterometer; (2) analysis of the variability of SIR-B data detected prior to processing for either azimuth compression or; possibly, range compression so that averages over relatively large footprints can be used; (3) processing of data of the form of (2) using algorithms that can recover the vertical pattern of the antenna.

Moore, R. K.↗
NASA NTRS1985

Antenna Axis Drive Torques for the 70-meter Antenna

Antenna axis speeds versus wind speeds are given in terms of dish size, hydraulic motor size, and the number of servo valves. An increase in the dish diameter of antenna is usually accompanied by increases in the axis torques required to drive the antenna against wind. The proposed increase in the diameters of the 64-m antenna dishes to 70 m (plus a noise shield) does require increased axis torques. The increased dish diameter causes the maximum azimuth and elevation torques to increase 48% and 43% respectively.

Mcginness, H. D.↗
NASA NTRS1985

Dilution jet configurations in a reverse flow combustor

Results of measurements of both temperature and velocity fields within a reverse flow combustor are presented. Flow within the combustor is acted upon by perpendicularly injected cooling jets introduced at three different locations along the inner and outer walls of the combustor. Each experiment is typified by a group of parameters: density ratio, momentum ratio, spacing ratio, and confinement parameter. Measurements of both temperature and velocity are presented in terms of normalized profiles at azimuthal positions through the turn section of the combustion chamber. Jet trajectories defined by minimum temperature and maximum velocity give a qualitative indication of the location of the jet within the cross flow. Results of a model from a previous temperature study are presented in some of the plots of data from this work.

Zizelman, J.↗
NASA NTRS1985

Progress on Experimental Impact Studies

Experimental impact studies were undertaken. Ejecta velocity distributions and related results from regolith targets were studied. The velocity distributions, energy partitioning, and related properties from 14 impacts at speeds 5 to 2321 m/s in vacuo into regolith-like fine powders were derived. Data are analyzed on: velocity and mass distributions as a function of azimuth around the crater during oblique impacts catastrophic disruption of spherical targets of variable strength, and catastrophic disruption of irregular-shaped natural rock targets and artificial granular aggregate targets.

Hartmann, W. K.↗
NASA NTRS1985

Interaction of Martian Flow Ejecta Blankets with Pre-existing Impact Craters: Morphological Observations

The evidence of interaction between impact flow ejecta blankets and pre-existing landforms such as craters, scarps, and wrinkle ridges may yield important clues as to the nature of the ejecta emplacement process. The morphology of flow ejecta blankets and the interactions of these blankets with pre-emplacement impact craters were characterized. About 80 small satellite craters on or in 3 well-expressed low ejecta parent impact craters were recognized. Interaction of the blanket with pre-existing structures was studied, and several types were described. These are: (1) infilling; (2) encroachment; (3) overflow; and (4) breaching. Examination of the overall morphology of three ejecta blankets reveals a range of thickness, from depths sufficient to completely bury craters in the 5 km diameter range in distal areas of the blankets, to very thin blankets which allow subtle pre-existing topography to be visible within a half the diameter of the parent crater. Radial and azimuthal symmetries appear to exist within the blankets over a range of morphologies. It also appears that there is a weak linear correlation between the diameter of craters with nearly 100% infilling and distance from the center of the parent crater.

Pieri, D. C.↗
NASA NTRS1985

Tectonics of the Valhalla Structure on Callisto

The surficial morphology of Callisto is dominated by large concentric patterns of ridges, scarps, and furrows. The largest one, Valhalla, shows a smooth central area 350 km in radius, surrounded by concentric sinuous ridges which extend as far as 600km from the center. Beyond the ridged area, scarps and furrows are observed as far as 2000 km. The global azimuthal distribution of the scarps and furrows of the outer ring (beyond 700 km from the center) was analyzed. It is proposed that the local geometry and the global distribution of scarps and furrows around Valhalla are the results of the reactivation of an old pattern by the Valhalla event. The coincidence of these local directions of a preexisting pattern (NW-SE and NE-SW) with the directions of the grids observed on most bodies observed so far in the solar system would indicate that this local pattern is a part of a global calistean grid.

Thomas, P. G.↗
NASA NTRS1985

Viking Lander Mosaics of Mars

The Viking Lander 1 and 2 cameras acquired many high-resolution pictures of the Chryse Planitia and Utopia Planitia landing sites. Based on computer-processed data of a selected number of these pictures, eight high-resolution mosaics were published by the U.S. Geological Survey as part of the Atlas of Mars, Miscellaneous Investigation Series. The mosaics are composites of the best picture elements (pixels) of all the Lander pictures used. Each complete mosaic extends 342.5 deg in azimuth, from approximately 5 deg above the horizon to 60 deg below, and incorporates approximately 15 million pixels. Each mosaic is shown in a set of five sheets. One sheet contains the full panorama from one camera taken in either morning or evening. The other four sheets show sectors of the panorama at an enlarged scale; when joined together they make a panorama approximately 2' X 9'.

Morris, E. C.↗
NASA NTRS1984

Development and testing of Parabolic Dish Concentrator No. 1

Parabolic Dish Concentrator No. 1 (PDC-1) is a 12-m-diameter prototype concentrator with low life-cycle costs for use with thermal-to-electric energy conversion devices. The concentrator assembly features panels made of a resin transfer molded balsa core/fiberglass sandwich with plastic reflective film as the reflective surface and a ribbed framework to hold the panels in place. The concentrator assembly tracks in azimuth and elevation on a base frame riding on a circular track. It is shown that the panels do not exhibit the proper parabolic contour. However, thermal gradients were discovered in the panels with daily temperature changes. The PDC-1 has sufficient optical quality to operate satisfactorily in a dish-electric system. The PDC-1 development provides the impetus for creating innovative optical testing methods and valuable information for use in designing and fabricating concentrators of future dish-electric systems.

Dennison, E. W.↗
NASA NTRS1982

A model containing blobs for the A ring of Saturn

Observations of the brightness distribution of Saturn's ring A from four separate years, including azimuthal variations, are calibrated and interpreted through the use of a scattering model. In this model the A ring is composed of elongated density enhancements (blobs) embedded in a ring of uniform density. The blobs are approximated by biaxial ellipsoids. Intensity observations at one tilt angle can be used in the model to predict the intensity at other tilt angles. Analysis shows that there must be matter between blobs characterized by an optical thickness = 0.45 and single scattering albedo = 0.70. A rough estimate, based on what appears to be shadowing of one blob by another, gives the ring area occupied by blobs as 5%.

Thompson, W.↗
NASA NTRS1982

Infrared observations of the Uranian rings

Maps of the Uranian rings at 2.2 microns and spectrophotometric observations covering 2.0 to 2.4 and 2.9 to 3.9 microns are discussed. The maps reveal a 2:1 azimuthal brightness variation whose amplitude and phase are consistent with the width variation and apsidal precession of the epsilon ring. Comparison with models based on stellar occultation data leads to an upper limit of 0.01 on the normal optical depth of any broad (5000 km wide), diffuse component of the ring system. A significant east-west asymmetry, corresponding to a brightening of the near side of the rings relative to the far side, is unexplained. The spectrum of the rings is flat over the range 2.1 to 3.9 microns. There is no spectroscopic evidence for the presence of H2O.

Nicholson, P. D.↗
NASA NTRS1985

Magnetic and thermodynamic structure of the solar corona during sunspot minimum

A model of the solar corona during sunspot minimum was constructed. It was suggested that pole-equator asymmetry is caused by interaction of global azimuthal electric currents in the corona and potential magnetic fields originating below the corona. The problem was reduced to a nonlinear ordinary differential equation for a structural function. Taking the difference in electron density between the equatorial plane and the polar direction from observations, the basic equation was solved and the global electric current distribution around the Sun along with the magnetic and thermodynamic structures of the solar corona was derived. The asymmetry between the two hemispheres, which can be due to the magnetic quadrupole, is considered in detail. It is shown that an additional quadrupole term in the magnetic field representation affects the position of polar coronal hole boundaries differently in the two hemispheres. As a result, the outflow from the two polar regions is found to be different.

Osherovich, V. A.↗
NASA NTRS1985

Comparisons of simultaneous vector magnetograms

Simultaneous vector magnetograms were obtained with the different magnetographs of the Okayama Astrophysical Observatory and the Sayan Mountain Observatory in October 1983. The data obtained show a good correspondence in general. The comparison makes clear something on the measuring accuracy of each magnetograph. Good correspondence is shown in circular and linear polarizations, and, in and near sunspots, of the velocity field. The azimuth of the magnetic fields show good agreement.

Makita, M.↗
NASA NTRS1984

Canadian Astronautics Limited's SARSAT ground stations

The SARSAT Local User Terminal (LUT) is described. The RF receiving subsystem is based on a conventional 3 m dish antenna mounted on an elevation-over-azimuth pedestal to permit tracking of the low altitude, near polar satellites. Only program tracking is used since orbit parameters and time must always be known precisely for use in position location. Operation of the LUT is split into real-time mode during which Doppler data are generated and stored, and post-pass during which data are sorted and position located. Location accuracy is to within 20 km.

Taylor, J. D.↗
NASA NTRS1984

Millstone Hill radar: Capabilities for S/T observations

During the past several years, the 440-MHz radar at Millstone Hill has been modified to detect coherent echoes from clear-air turbulence in the stratosphere/troposphere (S/T) over the altitude range 4-25 km. Two distinct modes of data acquisition have been developed, and data reduction programs have been completed for one of these modes. This mode (I-mode) transmits a 10 microsec (1.5 km) pulse on the fully steerable antenna. Typically, the antenna is set at a low elevation angle (e.g., 15 deg.) to reduce the altitude resolution to approximately 1 km., and power spectra are collected at some 40 range gates. The antenna may be scanned in azimuth to obtain the total wind vector, held fixed to monitor wave motion, or scanned in elevation to monitor the horizontal extent of the turbulent activity. This steerability gives Millstone a flexible system to focus on localized events, such as lee waves or convective storms. An additional advantage at low elevations is the relatively large Doppler shift of the signal, since the LOS velocity contains a large component of the horizontal velocity. This shift separates the turbulence signal sufficiently far from the ground clutter to allow the spectral moments to be readily inferred. Some 500 hours of S/T I-mode data have been reduced to geophysical parameters, and reside on a data base at Millstone Hill.

Loriot, G. B.↗
NASA NTRS1985

Source energy spectra from demodulation of solar particle data by interplanetary and coronal transport

The data on source energy spectra of solar cosmic rays (SCR), i.e. the data on the spectrum form and on the absolute SCR are of interest for three reasons: (1) the SCR contain the energy comparable to the total energy of electromagnetic flare radiation (less than or equal to 10 to the 32nd power ergs); (2) the source spectrum form indicates a possible acceleration mechanism (or mechanism); and (3) the accelerated particles are efficiently involved in nuclear electromagnetic and plasma processes in the solar atmosphere. Therefore, the data on SCR source spectra are necessary for a theoretical description of the processes mentioned and for the formulation of the consistent flare model. Below it is attempted to sound solar particle sources by means of SCR energy spectrum obtained near the Sun, at the level of the roots of the interplanetary field lines in the upper solar corona. Data from approx. 60 solar proton events (SPE) between 1956-1981. These data were obtained mainly by the interplanetary demodulation of observed fluxes near the Earth. Further, a model of coronal azimuthal transport is used to demodulate those spectra, and to obtain the source energy spectra.

Perez-Peraza, J.↗