Sounding of cometary nucleus via wideband radar in the Rosetta mission

Presents the radar sounding of comet nucleus layered surface for the Rosetta mission. The science objectives are the identification of the surface and subsurface layer material components and the depth measurement of the first layer, by using a two layered nucleus model. An in situ investigation by a light weight and low power consumption probe can be proposed; this is achieved by ground-radar pulse technology. Moreover, a wideband radar can be used by the orbiter: this solution leads also to the generation of the comet nucleus profile and surface images. The radar can also be used as a navigation aid. The aim of this paper is the definition of a electromagnetic (em) model of the cometary nucleus and the computation of the dielectric constants of the materials. The adopted hypothesis are the flatness and smoothness of the discontinuities: the electrical parameters of the regolith are variable only with depth. Using the measurement of the surface and subsurface reflectivities and of the time delay between the first and second received echo the nucleus parameters can be estimated by solving the “inverse problem”