Abstract : Little information is available on the composition of the planet's sub-surface. The search for potential water reservoirs, which may have persisted at kilometric depths is still relevant. The EM sounding appears as one of the most promising ways. A Ground Penetrating Radar EISS Electromagnetic Investigation of the SubSurface has been designed for the ExoMars mission and allowing the survey of the deep subsurface in mono and bistatic mode. We present results of studies conducted on the optimization of the EISS's electrical antenna which is composed of two loaded monopoles and on the impact of the angle between these two monopolies on the EISS. The electrical coupling between the antenna and the near subsurface was analyzed to estimate the permittivity of the geological top layer. Different techniques of data interpretation in terms of detection, three-dimensional localization and characterization of subsurface layers are proposed and evaluated using simulated data.