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At least 775 records · Page 43
All sourcesNASA NTRSDOE OSTI
NASA NTRS1971

Radar studies of the moon

Radar observation of lunar distance, motion and surface statistical nature, noting enhanced reflectivity associated with craters

Evans, J. V.↗
NASA NTRS1969

The laser radar above 30 kilometers

A short "state of the art' report on laser radar observations of the atmosphere at heights greater than 30 km is presented. Graphs of recent measurements of the Rayleigh backscattering function between 30 and 70 and above 50 kilometers are included.

Clemesha, B. R.↗
NASA NTRS1971

Martian craters and a scarp as seen by radar.

Radar observations of Mars with a surface resolution of 1.3 deg in latitude and 0.8 deg in longitude have been carried out during the opposition of 1971. With a precision in surface height measurement approaching 75 meters in regions of high reflectivity, it has been possible to measure the detailed characteristics of a number of craters. Many of these can be identified with craters shown in Mariner photographs of Mars. In addition, a scarp has been seen at 41 deg west, 14 deg south with an average slope of about 6 deg extending over about 40 kilometers.

Pettengill, G. H.↗
NASA NTRS1972

Skylab S193 and the analysis of the wind field over the ocean

The present status of the program to provide proof of concept for the idea that simultaneously observed radar scattering cross section measurements and passive microwave measurements can be used to determine the winds in the planetary boundary layer over the ocean, is given. The role of S193 in Skylab is providing the final clinching proof that an operational instrument will obtain data of great value to both meteorology and oceanography is described.

Pierson, W. J., Jr.↗
NASA NTRS1973

Simultaneous in situ electron temperature comparisons using Alouette 2 probe and plasma resonance data

The electron temperatures deduced from Alouette 2 diffuse resonance observations are compared with the temperature obtained from the Alouette 2 cylindrical electrostatic probe experiment using data from 5 mid-to-high latitude telemetry stations. The probe temperature is consistently higher than the diffuse resonance temperature. The average difference ranged from approximately 10% to 40% with the lower values occurring at the lowest altitudes sampled (near 500 km) and at high latitudes (dip latitude greater than 55 deg), and the larger values occurring at high altitudes and lower latitudes. The discrepancy appears to be of geophysical origin since it is dependent on the location of the data sample. The present observations support the view that the often observed radar backscatter - probe electron temperature discrepancy is also of geophysical origin.

Benson, R. F.↗
NASA NTRS1973

Topography and radar scattering properties of Mars.

High-resolution radar observations of Mars at a wavelength of 3.8 cm have been carried out at the Haystack Observatory for a period of about 6 months surrounding the 1971 opposition. The relative surface height variation with longitude over a band of Martian latitudes between about -14 and -22 deg has been derived from these observations with an error of about 75 m in the most favorable cases. At -14 deg latitude, the dielectric constant was found to increase steadily from about 1.7 at 70 deg W to about 5.0 at 110 deg W. Over the same interval the rms surface slopes vary from 2 to 1 deg.

Pettengill, G. H.↗
NASA NTRS1973

Lidar measurements of the variability of stratospheric particulates

Laser radar observations were made to provide information on the distribution of particulate material in the stratosphere between 33,000 feet and 98,000 feet. The observations are part of a program to assess the impact of climatic changes that may result from perturbation of the upper atmosphere by a world high-altitude aircraft fleet. Results are presented as vertical profiles of the scattering ratio and the aerosol backscattering ratio.

Russell, P. B.↗
NASA NTRS1974

Radar studies of the planets

The radar measurements phase of the lunar studies involving reflectivity and topographic mapping of the visible lunar surface was ended in December 1972, but studies of the data and production of maps have continued. This work was supported by Manned Spacecraft Center, Houston. Topographic mapping of the equatorial regions of Mars has been carried out during the period of each opposition since that of 1967. The method comprised extended precise traveling time measurements to a small area centered on the subradar point. As measurements continued, planetary motions caused this point to sweep out extensive areas in both latitude and longitude permitting the development of a fairly extensive topographical map in the equatorial region. Radar observations of Mercury and Venus have also been made over the past few years. Refinements of planetary motions, reflectivity maps and determinations of rotation rates have resulted.

Ingalls, R. P.↗
NASA NTRS1974

On the marginally stable saturation spectrum of unstable type I equatorial electrojet irregularities

Formulation of a self-consistent convective nonlinear theory of type I irregularities in the equatorial electrojet. It is found that a combination of three mechanisms - convective amplification, quasi-linear polarization electric field reduction, and nonlinear particle orbit diffusion damping - accounts for radar backscatter observations of a ubiquitous marginally stable (or 'constant ion-acoustic Doppler shift') saturation spectrum better than any of the three mechanisms treated separately. In particular, no spatially homogeneous theory without wave refraction can account for the observations. Wave refraction alone or with quasi-linear polarization electric field reduction is also inadequate. Wave refraction, quasi-linear polarization reduction, and particle orbit diffusion theory appear to account for type I observations at radar elevation angles less than 60 deg. Vertical type I backscatter cannot be explained without modifying the present laminar electrojet model.

Lee, K.↗
NASA NTRS1975

Relationships between motion on isentropic surfaces from 3-H rawinsonde data and radar echoes

Vertical motion in insentropic surfaces obtained at 3-h intervals conducted on 11 and 12 May, 1974 is related to convection indicated by radar echoes. Temporal and spatial changes in vertical motion are shown and demonstrated to be associated with areas of convection. Large vertical motion was calculated, and it is shown that vertical motion changes as much as 20 cm s (-1) in a horizontal distance of 300 km. The rate of change of vertical motion is demonstrated to be as large a 8 cm s (-1)h(-1) from data taken at 3-h intervals, while data taken at 12-h intervals the same day displayed a maximum rate of change of 2 cm s(-1)n(-1). Radar observations confirmed that the intensity of convection varies as a result of the atmospheric variability as detected by 3-h data but is invisible in data taken at 12-h intervals.

Overall, J. W.↗
NASA NTRS1976

Atmospheric structure and variability in areas of convective storms determined from 3-h rawinsonde data

The structure and variability of the atmosphere in areas of radar-observed convection were established by using 3-h rawinsonde and surface data from NASA's second Atmospheric Variability Experiment. Convective activity was shown to exist in areas where the low and middle troposphere is moist and the air is potentially and convectively unstable and has upward motion, in combination with positive moisture advection, at either the surface or within the boundary layer. The large variability of the parameters associated with convective storms over time intervals less than 12 h was also demonstrated so as to possibly produce a change in the probability of convective activity by a factor of 8 or more in 3 h. Between 30 and 60 percent of the total changes in parameters associated with convective activity over a 12-h period were shown to take place during a 3-h period. These large changes in parameters are related to subsynoptic-scale systems that often produce convective storms.

Wilson, G. S.↗
NASA NTRS1976

Electrical properties of Apollo 17 rock and soil samples and a summary of the electrical properties of lunar material at 450 MHz frequency

The dielectric constant and the voltage absorption length was measured for four Apollo 17 soil samples (73241, 74220, 75061, 76501) and for two Apollo 17 rock samples (76315 and 79135) at 450 MHz frequency. The dielectric constant and absorption length measurements made on the lunar samples are reviewed and related to the transition element concentration in these samples. The significance of the laboratory measurements for radar observations is discussed.

Gold, T.↗