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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 109 records · Page 6
All sourcesNASA NTRSDOE OSTI
NASA NTRS1989

Doppler radar observations of the evolution of a small convective storm during Cohmex

Doppler radar observations of a deep convection that developed along the Alabama-Tennesse border on July 14, 1986 are analyzed. The evolution and structure of the convective storm are examined. Two convective cores are observed and both having a radius of about 1 km and maximum reflectivities of about 5 dBz; a third cell is also detected later in the region between the northern and southern cells. It is noted that the northern cell is the most dominant possessing an updraft through the region of maximum reflectivity. Diagrams of the vertical structure of the cells are provided.

Moore, Patrick D.↗
NASA NTRS2001

Radar Observations of the Icy Galilean Satellites During 2000 Opposition

We report results of radar observation campaigns of Europa, Ganymede, and Callisto carried out during the November/December 2000 Jovian opposition using the Arecibo 12.6 cm, Goldstone 3.5 cm, and Goldstone/VLA 3.5 cm bistatic radars. Additional information is contained in the original extended abstract.

Harcke, L. J.↗
NASA NTRS1985

Radar observations of asteroids and comets

Radar techniques for the observation of asteroids and comets are reviewed, emphasizing the logical basis for inferring physical properties from radar measurements. Results to date are reviewed, focusing on some recent highlights of the research to demonstrate the synergism between radar and other ground-based techniques. Particular attention is given to the asteroids 2 Pallas, 16 Psyche, 2101 Adonis, and the comet IRAS-Araki-Alcock.

Ostro, S. J.↗
NASA NTRS1980

Radar observations of Saturn's rings at intermediate tilt angles

The 12.6-cm-wavelength radar observations of Saturn's rings, corresponding to ring-plane tilt angles of 18.2, 11.7, and 5.6 degrees, respectively, are reported. Measurements of geometric albedo and circular polarization ratio are used to investigate acceptable ring models and radar scattering properties of individual particles. Attention is given to the dependence of the rings' polarization properties on wavelength or tilt angle, or both. All large-particle monolayer models of Saturn's rings are ruled out; however, extended-layer models postulating ice or metal particles are compatible with the radar albedo measurements and are less severely restricted by the polarization data.

Ostro, S. J.↗
DOE OSTI2026

Anisotropic Melt Inclusions as a Confounding Signal for Ice‐Penetrating Radar Observations

Ice-penetrating radar is a powerful geophysical tool for understanding the subsurfaces of Earth, Mars, and icy moons. Radar reflectivity, attenuation, and birefringence are used to infer subsurface hydrology, englacial temperature, water content, and crystal orientation fabric. However, conventional radar sounding analyses either ignore melt or use classical mixing models which assume spherical melt inclusions, obscuring anisotropic contributions of melt. Here, we use geometric mixing models to calculate the reflectivity, attenuation, and birefringence of temperate ice containing anisotropic melt. We find that anisotropic melt can introduce significant deviations in radar measurements. For instance, melt anisotropy may impact reflectivity-based estimates of water content by up to 30% volume fraction, while attenuation-based estimates may vary by up to 43%. Critically, a melt volume fraction of just $f$ ~ 10 -5 can reproduce birefringence signals previously attributed to ice fabric. We conclude that melt anisotropy may significantly impact analyses of englacial hydrology, subglacial hydrology, and ice fabric.

58 GEOSCIENCES↗
NASA NTRS1975

The problem of regime summaries of the data from radar observations

Peculiarities of the radar information about clouds are examined in comparison with visual data. An objective radar classification is presented and the relation of it to the meteorological classification is shown. The advisability of storage and summarization of the primary radar data for regime purposes is substantiated.

Divinskaya, B. S.↗
NASA NTRS1990

Venus - Improved spin vector from Goldstone radar observations

Twenty-one radar images of the surface of Venus obtained between 1972 and 1982 have been compared to follow the motion of 28 distinct features. The delays and Doppler shifts of these features with respect to the subradar points on the various days were used in a nonlinear least-squares parameter estimation algorithm to refine the period and pole orientation of Venus. The period is found to be -243.022 + or - 0.003 days; the right ascension and declination of the pole are: alpha = 272.816 + or - 0.14 deg; beta = 67.218 + or - 0.05 deg (B1950). These standard error estimates attempt to include effects of systematic errors.

Slade, M. A.↗
NASA NTRS1983

Disdrometer measurements during a unique rainfall event in central Illinois and their implication for differential reflectivity radar observations

Understanding of the natural variability of rainfall is essential in order to assess radar's ability to estimate rainfall characteristics such as rainfall rate, rainfall water content and drop size distribution parameters. The two most useful measurements of rainfall for this purpose derive from ground-based disdrometers and aircraft-borne drop size spectrometers. Accordingly, this paper examines a time series of disdrometer measurements obtained during a unique rainfall event which occurred in central Illinois on October 6, 1982. The measurements are used to predict the behavior of radar observables (reflectivity factor and differential reflectivity) for application to the estimation of rainfall parameters. The results support previous theoretical predictions (Seliga and Bringi, 1976) and experimental results (Seliga et al., 1979, 1981; Bringi et al., 1982; Hall et al., 1980; Goddard et al., 1982) based upon the differential reflectivity (ZDR) radar technique.

Seliga, T. A.↗
NASA NTRS1985

Topographic mapping from interferometric synthetic aperture radar observations

The production of high-resolution topographic maps derived from interferometric synthetic aperture radar observations of the Earth is reported. Topographic maps are typically determined from stereo-pair optical photographs. Vertical relief causes the same terrain to appear in a slightly different projection for differing look angles, and this shift in appearance is interpreted in terms of the height of the terrain. The radar interferometric approach is related to the stereo technique in that the terrain is viewed at two different angles; however, in this case, the angular separation of the antennas is extremely small, on the order of a milliradian or less, as compared to tens of degrees for the optical case. Thus, the geometrical distortion and subsequent rectification correction algorithms are much less severe in the reduction of interferometric data.

Zebker, H. A.↗
NASA NTRS1986

Topographic mapping from interferometric synthetic aperture radar observations

The production of high-resolution topographic maps derived from interferometric synthetic aperture radar observations of the earth is reported. Topographic maps are typically determined from stereo-pair optical photographs. Vertical relief causes the same terrain to appear in a slightly different projection for differing look angles, and this shift in appearance is interpreted in terms of the height of the terrain. The radar interferometric approach is related to the stereo technique in that the terrain is viewed at two different angles; however, in this case, the angular separation of the antennas is extremely small, on the order of a milliradian or less, as compared to tens of degrees for the optical case. Thus, the geometrical distortion and subsequent rectification correction algorithms are much less severe in the reduction of interferometric data.

Zebker, H. A.↗
NASA NTRS2002

The Surface of Titan: Arecibo Radar Observations

The Arecibo 12.6 cm radar system was used to observe Titan in 1999, 2000 and 2001. The mean value of the radar albedo is 0.16 and the polarization ratio is 0.35. For some longitudes the echo has a specular component although most of the echo power is contained in a diffuse component. Additional information is contained in the original extended abstract.

Campbell, D. B.↗
NASA NTRS2004

Radar observations of recent Mars landing sites

This paper will present results of terrestrial delay-Doppler radar observations of the landing sites, predictions for the surface properties that will be encountered, and, after successful landings, correlation between the predicted and observed surface properties. The in-situ observations made by both missions serve as ground truth for the validation of the high resolution radar mapping results.

Slade, M. A.↗
NASA NTRS1990

Radar observations of precipitation growth and evolution within the anvil region of a MCS

Doppler radar observations of the growth and evolution of precipitation (reflectivity factor) and associated mesoscale motions within the anvil region of an evolving mesoscale convective system (MCS) are presented. This MCS was observed during the Cooperative Huntsville Meteorological Experiment conducted over northern Alabama and central Tennessee during June and July, 1986. During the latter stages of the approximate eight-hour lifetime of this MCS, an extensive region of stratiform precipitation was observed. Attention is given to the initial appearance and subsequent evolution of precipitation within the stratiform region of the MCS, and the relation to the mesoscale flows that are seen within the system.

Knupp, Kevin R.↗
NASA NTRS1985

Design and benefits of a multibeam Earth Observing Radar

The oceanographic rationale is described for continuing to advance the state of the art in satellite radar altimetry, and the expected capabilities of a multibeam Earth Observing Radar are noted. At the end of this decade, there is the possibility that altimeters may be in orbit aboard the American TOPEX, the ESA ERS-1, and the French SPOT satellites at the same time. The TOPEX version will be the most precise altimeter yet built. Global ocean circulation will be measured by using TOPEX to monitor the elevation changes across the ocean basins due to oceanic currents. It will then be possible to monitor the 'mean' circulation patterns in the oceans. The multiple beams of EOR might be used to measure the curvature of the topographic surface. The use of curvature is especially beneficial because it is directly related to ocean circulation, which is a function only of the Laplacian of the topographic height field in a given area. With the EOR, that height field will be known and ocean circulation can be immediately computed.

Parsons, C. L.↗
NASA NTRS1986

Sondrestrom radar observations of the effect of the IMF B(y) component on polar cap convection

Sondrestrom incoherent-scatter radar measurements of plasma drift in the auroral oval and the polar cap are used to examine the effect of the IMF B(y) component in the dusk, midnight, and dawn sectors. The individual radar observations are briefly reviewed, and the average convection patterns obtained by binning the drift data for the two orientations of the IMF B(y) component are shown. These patterns are compared to the various models of convection that have been proposed. None of the models seem to reproduce the observed convections well, although some features of the models are seen in the radar data.

De La Beaujardiere, O.↗
NASA NTRS2002

Arecibo Radar Observations of Near-Earth Asteroids: A Study in Heterogeneity

Characterization of the rotation state and structure of near-Earth asteroids through radar observations using the Arecibo and Goldstone planetary radar systems shows the remarkable variety of these objects, and suggests variety of formation and modification mechanisms. Additional information is contained in the original extended abstract.

Nolan, M. C.↗
NASA NTRS2000

Radar observations and physical model of asteroid 6489 Golevka

We report 8510-MHz (3,5-cm) radar observations of the Earth crossing asteroid (ECA) 6489 Golevka (1991 JX) obtained between June 3 and June 15, 1995, at Goldstone, the Very Large Array and the Evpatoria (Ukraine) and Kashima (Japan) radio antennas.

Astroids orbits 6489 Golevka toutatis↗