Martian topography and surface properties as seen by radar: The 1971 opposition

Taking advantage of the favorable opposition of 1971, the Goldstone radar system, operating at 2388MHz, was used to scan the Martian surface. Measurements of altitude and reflected power were taken approximately every 3 days. Each measurement represents an area 8km E-W × 80km N-S, the highest resolution attained to date. Altitude measurements obtained on different observing days were combined to produce altitude profiles for three complete rotations, each at different latitudes. Large-scale variations in altitudes cover a range of 14km. Altitude changes of 5 in 30km of longitude were observed. The altitude profiles show the heavy cratering of the surface, and several large craters (50–100km) 1–2 km deep are easily seen. Reflected power for different angles of incidence was measured, yielding the scattering properties of the surface as a function of longitude. Correlation was found between the peak intensity of the reflected signal and the width of the scattering function. The average relationship between the intensity and the width suggests a power reflection coefficient of at least 0.064 ± 0.012. Departures from the average are interpreted as deviations in the reflection coefficient from the mean value. These variations are presented as a function of longitude for each of the three rotations.