HR: 0800h
AN: P31C-0215    [Abstracts]
TI: An Estimation Of The Geoelectric Features Of Planetary Shallow Subsurfaces With TAPIR Antennae
AU: * Le Gall, A
EM: alg@cetp.ipsl.fr
AF: CETP, 4, avenue de Neptune, Saint-Maur-des-Foss‚, 94107 France
AU: Reineix, A
EM: reineix@unilim.fr
AF: IRCOM, 123, avenue Albert Thomas, Limoges, 87060 France
AU: Ciarletti, V
EM: ciarletti@cetp.ipsl.fr
AF: CETP, 10-12, avenue de l'Europe, Velizy, 78140 France
AU: Jean-Jacques, B
EM: jjb@cetp.ipsl.fr
AF: CETP, 4, avenue de Neptune, Saint-Maur-des-Foss‚, 94107 France
AU: Ney, R
EM: ney@cetp.ipsl.fr
AF: CETP, 4, avenue de Neptune, Saint-Maur-des-Foss‚, 94107 France
AU: Dolon, F
EM: dolon@cetp.ipsl.fr
AF: CETP, 4, avenue de Neptune, Saint-Maur-des-Foss‚, 94107 France
AU: Corbel, C
EM: Corbel@cetp.ipsl.fr
AF: CETP, 10-12, avenue de l'Europe, Velizy, 78140 France
AB: Exploring the interior of Mars and searching for water reservoirs, either in the form of ice or of liquid water, was one of the main scientific objectives of the NETLANDER project. In that frame, the CETP (Centre d'‚tude des Environnements Terrestre et Plan‚taires) has developed an imaging ground penetrating radar (GPR), called TAPIR (Terrestrial And Planetary Investigation by Radar). Operating from a fixed position and at low frequencies (from 2 to 4MHz), this instrument allows to retrieve not only the distance but also the inclination of deep subsurface reflectors by measuring the two horizontal electrical components and the three magnetic components of the reflected waves. In 2004, ground tests have been successfully carried out on the Antarctic Continent; the bedrock, lying under a thick layer of ice (until 1200m), was detected and part of its relief was revealed. Yet, knowing the electric parameters of the close subsurface is required to correctly process the measured electric and magnetic components of the echoes and deduce their propagation vector. In addition, these electric parameters can bring a very interesting piece of information on the nature of the material in the shallow underground. We have therefore looked for a possible method (appropriate for a planetary mission) to evaluate them using a special mode of operation of the radar. This method relies on the fact that the electrical characteristics of the transmitting electric antennas (current along the antenna, driving-point impedance.) depend on the nature of the ground on which the radar is lying. If this dependency is significant enough, geological parameters of the subsurface can be deduced from the analysis of specific measurements. We have thus performed a detailed experimental and theoretical study of the TAPIR resistively loaded electrical dipoles to get a precise understanding of the radar transmission and assess the role of the electric parameters of the underground. In this poster, we will analytically prove the sensitivity of TAPIR antennae to subsurface nature. Besides, a numerical code, based on the FDTD method, has been built to simulate with accuracy radar operation and its coupling with the environment. Results from simulations will be then compared to in-situ measurements collected in three different sites. Eventually, we will see that the inferred geoelectrical values characterize only a thin layer of the subsurface.
DE: 5422 Ices
DE: 5430 Interiors (8147)
DE: 5460 Physical properties of materials
DE: 5464 Remote sensing
SC: Planetary Sciences [P]
MN: Fall Meeting 2005