Interpretation of angular dependence of backscattering from the Moon and Venus

Abstract

The small crater Heinsius A which exhibited th e radar e nhancem e nt is th e bri ght s pot indi cated by the arrow.Also, it is known that durin g a lun a r eclip se th e rayed crater s ex hibit a differen t coo lin g rat e than th e rest of th e lunar s urface. Th e mos t re ce nt measure· ments of a lunar eclipse in Dece mb er 1964, show that many other craters also s ho w thi s a nam olou s coo lin g behavior. On e of th e ne wly di scove red " th ermalanamolou s" cra ters ha s bee n te nt atively identified as He in siu s A, the c ra te r whi c h was bright under full moon and s howe d a radar e nhan ce me nt. The optical, thermal, and radar res ults can be explained by localized areas of bare, ex posed , and com pact roc k.In conclus ion , lunar radar ec hoes were examined in delay and frequ e ncy in a mann e r such that ret urns were reflected from localized areas on th e lunar surface. Th e ma ppin g of th ese re turn s s howe d that young and r aye d cra ters have e nh a nced radar sca tte rin g. Th e c raters which s how th ese rad a r e nh a nceme nts a lw ays a pp ear bri ght on th e full moon a nd from th e latest infrared res ult s, appear to be a namo lous in that regim e also. The resu lt s a t all wav ele ngth s ca n be exp lain ed if th ese are loca li zed a reas of bare, exposed, and co mpacted roc ks.Although this pape r concerned the radar behavior of young a nd rayed craters it should be noted that th e mountainou s regions we re s hown to re fle ct more power than th e maria regions. Th e e nhan ce ments we re mu c h less modes t th a n th ose for th e crate rs . For example, mountainous region s reR ected 11f2 to 2 times as much power as the maria region , while scattering e nhancements of craters s how th ey reflec ted up to 10 or 20 times as much power as o ther areas on the moon .Discussion Following Thompso n's Paper A previous ly de ri ved formula. ex press in g th e variation of the me an power bac kscatte red from the rough s urface of a planet with th e delay tim e or angle of inc id e nce by taking into account both th e co mpo site roughn ess of th e s urface a nd shadowing e ffec ts, is c hecked against ne w data from th e Moon and Venus a t fiv e diffe rent wav e length s. Th e a gree ment with the lunar data is very good and leads to ce rtain co nc lu s ions on th e nature of the lunar s urface. Th e data on Venu s are also in good agree ment and indi ca te that its s urface is smooth er than that of the Moon , but with an abundance of small s tru cture.

Impact of Phonon Surface Scattering on Thermal Energy Distribution of Si and SiGe Nanowires

“…1c ]. It is well understood 40 41 that shadowing plays an important role in accurately predicting the scattered intensity, particularly at grazing incident angles. To account for this phenomena mathematically, a shadowing function defined as the ratio of the unscreened surface to the total surface is introduced, which takes the value unity for points not in shadow and zero for shaded parts of the surface.…”

The Moon as a calibration target of convenience for VHF‐UHF radar systems

“…Values of C and K from (4) are given in Table 1 for a few wavelengths. These values incorporate both the quasi-specular and diffuse scattering components and have been obtained by fitting (4) to experimental results [Beckmann and Klemperer, 1965] except where noted.…”

Radar Signatures of the Planets

“…The J e t Propulsion Laboratory results yielded the echo power spectrum in frequency, but these too can be converted to yield the angular power spectrum (Carpenter, 1964). Beckmann and Klemperer (1965) have examined these results in an attempt to find a wavelength dependence, but no clear-cut dependence can be recognized as in the case of the moon. The majority of the results show a slightly less steep fall in echo power with delay than shown in FIGURE 18, but this may simply reflect the poorer resolution achieved.…”