Bistatic Deep Soundings with the Hf Gpr Tapir in the Egyptian White Desert

Introduction: In the frame of the NetLander mission, the Centre d’étude des Environnements Terrestre et Planétaires (CETP) has developed an impulse ground penetrating radar (GPR) operating at very low central frequencies from 2 to 6 MHz [1]. This instrument, named TAPIR (Terrestrial And Planetary Investigation Radar), aims at exploring the geological features in the deep Martian subsurface and at the detection of liquid water underground reservoirs. This GPR was designed to retrieve, from a single fixed location, both the distance and the direction of the reflecting structures. This can be achieved by determining the propagation vector of reflected waves, through measurements of two horizontal electrical and three magnetic components of the reflected waves. This direction information is essential not only to characterize the sub-surface structures but also to discriminate between the echoes coming from the subsurface and those due to the surface clutter, In-situ measurements on well documented soils that are analogues of the expected Martian soils are crucial to validate the performances of the instrument. In 2004, ground tests were successfully carried out on the Antarctic continent with a mono-static GPR prototype [2]. In November 2005, an updated version of the instrument working either in monostatic or in bi-static mode was tested in the Egyptian White Desert. Complementary sounding investigations were jointly conducted on the same site by research teams from the LPI (Lunar and Planetary Institute) [3] and the SwRI (Southwest Research Institute) [4]. They will provide independent information which will help the interpretation of our GPR data.