Evidence that the Moon is a rough scatterer at radio frequencies

Abstract

Radar echoes from the moon have been observed at 400 Mc/s for the purpose of determining the scattering properties of the moon. The results go beyond the investigations of other authors who claim that the moon is a quasi‐smooth reflector having a range depth of less than 600 μsec. Results described in this report indicate that, although the moon behaves as a quasi‐smooth reflector in the 0‐ to 600‐μsec range depth, beyond this range the moon behaves as a uniformly rough scatterer, giving echoes out to 1 lunar radius or the limit of visibility of the moon's surface from the earth. An empirical fit to the integrated range versus time display provides an angular scattering law for each infinitesimal area of the surface given by: P(ϕ) ∝ [(sin θ)/θ]20±6+1/10 A procedure for mapping the details of the moon's surface by radar, using range and Doppler shift coordinates, is suggested. This technique does not require angular resolution.

Radar studies of the Moon

“…The observations of Trexler , Yaplee, et al, and H ey and Hughes indi cated that ec hoes come only from a portion of the surface near the center of the di s k. This proved to be a consequence of the limited sensitivity of their equipment. Pettengill [1960] and Leadabrand et al, [1960] showed that echoes could be measured all th e way out to the limbs with a sufficiently powerful radar system. The first truly quantitative measurements of echo power ve rs us delay from the leading edge to the limb were performed by P e ttengill [1960] and Pettengill and H e nry [1962a] a t a wavelength of 68 cm using 65-f-tSec pulses.…”