The WISDOM (500MHz - 3GHz) GPR is one of the instruments that have been selected as part of the Pasteur payload of ESA's 2018 ExoMars Rover mission. One of the main scientific objectives of the mission is to characterize the nature of the shallow sub-surface on Mars and WISDOM has been designed to explore the first ~ 3 meters of the sub-surface with a vertical resolution of a few centimetres. In order to illustrate and quantify the WISDOM performance, measurements in cold artificial and controlled conditions have been performed by the prototype. The objectives of this experiment were the detection of home made internal layering and the possible detection of a wedge included in the permafrost filled with different material with known characteristics. Some results and comparisons with a simple simulation are presented here and show the WISDOM performances.

The Water Ice Subsurface Deposit Observation on Mars (WISDOM) Ground Penetrating Radar (GPR) is one of the instruments that have been selected as part of the Pasteur payload of the European Space Agency's (ESA's) 2018 ExoMars Rover mission. The main scientific objectives of the mission are to search for evidence of past and present life and to characterize the nature of the shallow subsurface. The Rover is equipped with a drill that can sample the subsurface down to a depth of approximately 2 m. The WISDOM GPR is the only instrumentation capable of obtaining information about the nature of the subsurface along the Rover path before drilling. WISDOM has been designed to explore the first ~3 m of the subsurface with a vertical resolution of a few centimeters. The paper presents a description of the WISDOM instrument with a particular emphasis on the electronic architecture and antenna design that have been chosen to meet the challenging technical objectives. Some preliminary measurements obtained with the prototype are given to illustrate the instrument's potential performance.

In the frame of the European Space Agency's 2016 ExoMars mission, the Electromagnetic Investigation of the SubSurface (EISS) ground-penetrating radar has been designed and developed to perform deep soundings of the Martian subsurface from the surface. The EISS is designed to take advantage of the potential for bistatic radar investigations of the Martian subsurface between the fixed station (Lander) and the mobile platform (rover) and to characterize the 3-D structure and stratigraphy of the subsurface at depths ranging from 100 m to a few kilometers out to a 1-km radius around the lander. The EISS makes use of an electric dipole antenna made of two identical 35-m resistively loaded monopoles to transmit (and also receive in a monostatic mode) the high-frequency signal. However, the EISS's most innovative capability is its potential for bistatic operation, made possible by the accommodation of a small magnetic sensor on the rover (as initially planned for the ExoMars mission) which can measure the magnetic field (all three components) of the received waves whatever the direction and orientation of the rover. The aim of this paper is to show that the two monopoles of the antenna must be deployed on the surface in nearly opposite directions but not aligned to ensure good volume coverage around the transmitter. This paper is based on Finite Difference in Time Domain (FDTD) electromagnetic simulations. The simulated data have been used to study the impact of the angle between these two monopoles on the instrument performance.

Terrestrial And Planetary Imaging Radar (TAPIR) is an innovative high-frequency ground-penetrating radar (GPR) developed in the frame of the Martian NetLander mission to probe the subsurface down to kilometric depths. Unlike most GPRs, TAPIR is able to image underground reflectors with stationary antennas. In this paper, after a brief presentation of the instrument, we describe the method developed to interpret data collected during the RAdar of NEtlander in Terre AdÉlie (RANETA) field survey in Antarctica. This method consists of retrieving the direction of arrival of each detected echo through the measurement of five components of the electromagnetic field (the three magnetic components and the horizontal components of the electric field). Thus, both the range and the direction of each individual reflection or diffraction due to the ice–bedrock interface are resolved. We validated this method on finite-difference time-domain numerically simulated data for different subsurface configurations before applying it to RANETA observations. In particular, the irregular topography of the bedrock in two sounding sites was revealed. We discuss the accuracy of our results.

In the frame of the NETLANDER project, we have developed a ground penetrating radar (GPR) aimed at initial observations of the geological features in the deep Martian subsurface and the detection of potential liquid water reservoirs. Initial ground tests at 2, 3 and 4 MHz were recently performed on the Pyla Dune, which is a sand dune nearly 100 meter high along the south-west Atlantic coast in France. The horizontal reflecting layer located at the base of the dune together with the known permittivity value of the sand offer the opportunity to test the performance of the device in a rather well-documented and simple environment. These first experimental results are reported in the paper. We will focus on the precise measurement of the electric antenna characteristics and the analysis of the backscattered signals using both electric and magnetic components of the received field. Comparisons with numerical simulations taking into account the actual environment of the GPR are also presented for comparisons.

The study presented here is deals with the effect of bare soils roughness (including soil tillage and state of degradation due to rain fall) upon microwave scattering. Many theoretical as well as experimental studies have already been completed to point out the influence of soil roughness on backscattering. Nevertheless, the interpretation of radar measurements in terms of soil roughness still remains a difficult task given the geometrical complexity of real soils and the influence of soil moisture. Electromagnetic simulations of the radar signal are an essential step to understand the influence of such parameters on the back-scattered signal. For the purpose of this paper, a data base of real bare soil geometrical descriptions retrieved by using a stereovision method is used and the back-scattered signal is obtained for each kind of soil by a rigorous differential electromagnetic method.

The paper first presents an experimental set-up using a helicopter, which was realized to study the wide band and variable mobile satellite propagation channel. The first statistical characterizations stated are described. More specifically, the authors present cumulative distributions of narrow band and wide band excess path loss as a function of the elevation angle, as well as distribution functions of some frequency selectivity parameters.>