Interpreting radar scattering: Circular-polarization perspectives from three terrestrial planets

Three topics are addressed in this thesis.; Radar results from Doppler-only and delay-Doppler techniques are used to certify a landing site for the Pathfinder spacecraft. The sites examined are all appropriate from an elevation and regional topographic point of view. The Hagfors model allowed comparative estimates of surface roughness: Ares Vallis has {dollar}Thetasb{lcub}rm rms{rcub}{dollar} = 4.8{dollar}spcirc pm{dollar} 1.1{dollar}spcirc{dollar}. This is similar to previous measurements of the Viking Lander 1 region ({dollar}Thetasb{lcub}rm rms{rcub}{dollar} = 6{dollar}spcirc{dollar}). Tritonis Lacus is rougher with {dollar}Thetasb{lcub}rm rms{rcub}{dollar} = 5.6{dollar}spcirc pm{dollar} 0.6{dollar}spcirc{dollar}, while NW Isidis is very smooth with {dollar}Thetasb{lcub}rm rms{rcub}{dollar} = 1.8{dollar}spcirc pm{dollar} 0.2{dollar}spcirc.{dollar} These results are compatible with the prediction that the radar roughness at Pathfinder's Ares Vallis landing site will resemble that of the Viking Lander 1 site.; The controversy surrounding the anomalous radar behavior of Venus highlands is explored. The radar controversy alternately ascribes the high reflectivities to high dielectric constant materials or to multiple-scattering effects. We present new 3.5 cm dual circular-polarization radar maps of Venus, analyzing the Beta Regio. Diffuse scattering is important in Beta. We find a strong correlation of the SS albedo with altitude, {dollar}sigmasb{lcub}rm SS{rcub} propto 0.3Rsb{lcub}rm p{rcub}.{dollar} Also, {dollar}sigmasb{lcub}rm OS{rcub}propto0.7Rsb{lcub}rm p{rcub}.{dollar} The radar anomalies must therefore be consistent with a diffuse scattering mechanism. In Beta {dollar}musb{lcub}rm c{rcub} >{dollar} 0.5 in general, with {dollar}musb{lcub}rm c{rcub}{dollar} reaching 0.8 between Rhea and Theia Montes. In general though, the spatial resolution of the data from this experiment is not sufficient to unequivocally resolve the planetological debate.; The nature of the scattering processes from cold planetary ices is addressed. This topic arose from the unique radar signatures of icy satellites and planetary polar ice deposits, also recently observed on Greenland. Here, a survey is made of high altitude sites to discover if the Greenland percolation zone scattering behavior is wide-spread on the Earth. We surveyed the dataset of the 1994 missions of the Shuttle Imaging Radar. This instrument (SIR-C) obtains full-polarization information. Such data allow reconstruction of circular polarizations for planetary comparison. The search was fruitful. Hundreds of square kilometers in western Tibet and the Central Andes display radar scattering behavior similar to that in Greenland, and therefore resembling cold planetary ices.