THE RADAR SYSTEM FOR THE EXPLORATION OF TITAN

In the field of the exploration of the Solar System NASA and ESA have jointly planned two cornerstone missions whose aim is the close observ ation of two largely unknown planetary bodies: Titan (Cassini mission) and comet nuclei (Rosetta mission). Our attention in this paper will be devoted to the first one, however some results of this study can be applied also to the second one. Titan is one of Saturn's moons and is characterized by the presence of a dense atmosphere, opaque for optic al sensors. Therefore radar data are the only ones at least theoretica lly capable of giving relatively detailed informations about the geomo rphologic structure of Titan. As a matter of fact the radar cross-sect ion depends on both the dielectric constant of the target by means of the Fresnel reflectivity and on its surface roughness. Moreover if the attenuation is sufficiently low, the radar in principle could be able to detect subsurface discontinuities as well. The above consideration s hold true only if a well-suited analytical model accounting for surf ace backscattering is known. All throughout this paper the radar cross -section of planetary bodies will be evaluated in the case of high-res olution radars.