Accession Number : AD0628197

Title :   LUNAR RADAR REFLECTIONS,

Corporate Author : ARECIBO IONOSPHERIC OBSERVATORY PUERTO RICO

Personal Author(s) : Pettengill,G.

Report Date : 1965

Pagination or Media Count : 16

Abstract : The radar cross section of the moon has been measured over a frequency range of about 10 octaves, stretching from 7.84 m to 8.6 mm. Within the accuracy of measurement, which in only a few cases exceeds a factor of 2, there is no significant frequency dependence. The mean of all measurements yields a value of 0.07 of the geometrical (disk) cross section. The angular scattering law has also been determined over a wide range of frequencies, although the best measurements appear to lie in the region from 70 to 0.86 cm. There is a marked frequency dependence both in the mean surface slopes and in the fraction of surface which appears to scatter roughly. At the longer wavelengths the mean surface slope is about 1 in 7, while in the millimeter region the corresponding value approaches 1 in 2. The division of power between the quasi-specular peak corresponding to normal reflection from large smooth areas and the largely nondirectional scattering from rough areas varies from 4 to 1 (favoring quasi-specular) at 68 cm to 1 to 6 (favoring rough) at 0.86 cm. The measurements described above may be used to deduce a surface dielectric constant of about 3. For most likely surface materials this requires a bulk density of about one-half that of siliceous rocks typical of the earth's surface. This value is larger than that deduced for the visible lunar surface and undoubtedly corresponds to conditions a few meters below. (Author)

Descriptors :   (*RADIO ASTRONOMY, MOON), (*MOON, RADAR REFLECTIONS), (*RADAR REFLECTIONS, MOON), EXTRATERRESTRIAL TOPOGRAPHY, RADAR CROSS SECTIONS

Subject Categories : Astrophysics

Distribution Statement : APPROVED FOR PUBLIC RELEASE