
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 quasispecular peak corresponding to normal reflection from large smooth areas and the largely nondirectional scattering from rough areas varies from 4 to 1 (favoring quasispecular) 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 onehalf 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