Symposium on Radar and Radiometric Observations of Venus during the 1962 Conjunction: Radar scattering from Venus and the Moon

Abstract

A statistical theory for the radar backscatter function for a planetary surface will be derived. The physical basis of the theory involves combining two random variables which represent height variations and horizontal scattering lengths to form the probability distribution function for surface slopes. Two classes of distribution functions representing the two random variables are studied: those related to the normal distribution, and those related to the exponential distribution. These two classes result in slightly different distribution functions for slopes. Each of the slope functions contains a single parameter which is shown to be the ex- pectation value of the slopes, i.e., the mean effective slope. The probability density function of slopes is to be directly related to the radar backscatter func- tion under the assumption of geometrical optics. These functions are applied to radar observations of the moon at wavelengths of 3.6, 10, 12.5, and 68 cm and it is shown that the exponential statistics yield slightl superior results. The theory is applied to radar observations of Venus made at wavelengths of 12.5 and 68 cm in an attempt to deduce the mean slope of Venus and the Venusian rotational rate. It will be shown that Venus appears very smooth at radar wavelengths; i.e., the mean slope parameters are small relative to those for the moon. Values of the intrinsic angular velocity are computed from the 12.5-cm radar spectral observations of Venus and are found to be between the limits of 4.5X 10- and 2.OX 10-2 rad/sec. The spread in this result arises from the difficulties in determining the wavelength dependence for the slope parameters determined from the radar data.