UWB Vivaldi Antenna Array Lower Band Improvement for Ground Penetrating Radar Applications

This paper concerns a ground penetrating radar system (GPR) presenting beam forming ability. This ability is due to a great flexibility in the emission of wavefronts. The innovative concept is to use an array of antennas which can reconfigure itself dynamically, in order to focus on a desired target. This antennas system can act as a new microwave sensor to detect and characterize buried targets in an inhomogeneous medium which is the case study in various application fields such as geophysics, medical, planetology… Its electronics are in development with the DORT (Time reversal technique) method integration for optimizing the localization of buried target. This paper aims are to present the antenna optimization used in the GPR applications. Typical antennas used in GPR are generally Vivaldi ones directly on the ground. Especially, in the context of the space mission ExoMars 2020, the radar antenna is set on a mobile station at a distance of about 30 cm from the ground to avoid any contact. However, they are limited by their important size, due to the lowest frequency of their bandwidth. Results of this work concern an increase of the antenna bandwidth by shifting the lower-band limit, making it a UWB type [500 MHz - 4 GHz] without changing its size. As low frequency waves can spread deeper into probed medium, this optimization can improve the radar data inversion performances

Analog Mars Rover Service as a Robotic Hardware and Team Building Platform

Magma White is an analog Mars rover platform created by ABM SE and offered to the developers of scientific equipment built for space exploration missions, who want to test their devices at low- and mid- Technology Readiness Levels in demanding conditions of desert, Alpine and polar regions or artificial environments. The rover offers a remote access to the payload through the Magma White mission control system. The paper summarizes the background of the analog solution. It covers universal interfacing setup and issues related to the team and technological partners, who supply elements of the payloads. Two analog missions provide a case study: Dachstein 2012, when “WISDOM” ground penetrating radar for Exomars was tested onboard Magma White, and Morocco 2013, with “L.I.F.E.” payload and complete remote access from Europe

WISDOM GPR designed for shallow and high-resolution sounding of the martian subsurface

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 $sim$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

On the detection of polycyclic aromatic hydrocarbons within dynamic surface features on Mars

The aim of this thesis is to identify suitable environments for the detection of organic signatures on the Martian surface, to produce diagnostic spectra for organics in various Mars analogues, to establish the detectability limit of those organics using laboratory experiments and then compare laboratory results to measurements from Mars. The organics searched for in this work are Polycyclic Aromatic Hydrocarbons (PAHs), which are considered to be ‘building blocks’ for life, and can be a biomarker for extant life; they are abundant on Earth and throughout the universe, but so far are conspicuously absent on Mars, likely due to the high levels of ultraviolet radiation present on the Martian Surface. Therefore, dynamic processes on Mars that uncover previously shielded material on the Martian surface are identified, and various sites examined, to look at their suitability as potential candidates for PAH detection. The Martian South Polar Residual Cap (SPRC) has been chosen as a primary study site due to the abundance of CO2 ice sublimation features known as Swiss Cheese Terrain (SCT). These quasi-circular pits exhibit seasonal and long term retreat, exposing dust that had previously been trapped within the ice. The morphology and compositional changes of SCT over time are examined, and laboratory experiments in environmental cells have been carried out to establish base-line spectra for PAHs in SPRC and Mars regolith analogues, as well as the minimum amount of PAH necessary for detection from orbit by the Compact Reconnaissance Imaging Spectrometer for Mars (CRISM). In addition, Recurring Slope Lineae (RSL) sites and analogues have been examined to provide baseline spectra and detectability limits for PAHs in non-polar dynamic features. This work intends to shed light on the question of these ‘missing’ organic molecules on Mars, and assist in the search for life on the Red Planet

Characterization of rocks buried in the subsurface by the GPR WISDOM/ExoMars 2020

International audienceThe search for evidence of past life on Mars is the main objective of the ESA-Roscosmos ExoMars Rover mission. Given the hostile environment at the surface, if such evidence is to be found anywhere, it will most likely be in the subsurface. This is why the ExoMars rover mission has been optimized to investigate the subsurface. Among the instruments accommodated onboard the Rover, the polarimetric ground penetrating radar WISDOM (Water Ice Subsurface Deposits Observation On Mars, Ciarletti et al., 2011) has been designed to investigate the shallow subsurface and search for the most favorable locations where to drill and collect samples for analysis. WISDOM is able to probe down to a depth of few meters with a vertical resolution of a few centimeters, and will provide key information on the geological context of the environment.In particular, insights into density, size and shape of the rocks buried beneath the rover would be clues for a better understanding of the geological and hydrological history of the Rover site. In addition, the density and size of the buried rocks will have to be taken into account for the safety of the drilling operations.In this paper, we will focus on the ability of WISDOM to detect, localize and characterize (in terms of size and shape), rocks in the shallow subsurface of Mars. More specifically, we use a 3D numerical code based on the Finite Difference in Time Domain method to model the antenna system of WISDOM and simulate the instrument operations on realistic environments with buried rocks. In this approach, size-frequency distribution of rocks in agreement with observations from orbit and by cameras operated from the Martian surface will be considered. We will present results of simulations for different density and shape of buried rocks, including critical configurations where the density of rocks is too high to allow individual detection of rocks. In addition, we will present experimental data for comparison with the simulated data.References:V. Ciarletti, C. Corbel, D. Plettemeier, P. Caïs, S. M. Clifford, and S. E. Hamran, "WISDOM GPR Designed for Shallow and High-Resolution Sounding of the Martian Subsurface " Proceedings of the IEEE, vol. 99, no. 99, pp. 1-13, 2011