The WISDOM Radar: Unveiling the Subsurface Beneath the ExoMars Rover and Identifying the Best Locations for Drilling

The search for evidence of past or present life on Mars is the principal objective of the 2020 ESA-Roscosmos ExoMars Rover mission. If such evidence is to be found anywhere, it will most likely be in the subsurface, where organic molecules are shielded from the destructive effects of ionizing radiation and atmospheric oxidants. For this reason, the ExoMars Rover mission has been optimized to investigate the subsurface to identify, understand, and sample those locations where conditions for the preservation of evidence of past life are most likely to be found. The Water Ice Subsurface Deposit Observation on Mars (WISDOM) ground-penetrating radar has been designed to provide information about the nature of the shallow subsurface over depth ranging from 3 to 10 m (with a vertical resolution of up to 3 cm), depending on the dielectric properties of the regolith. This depth range is critical to understanding the geologic evolution stratigraphy and distribution and state of subsurface H2O, which provide important clues in the search for life and the identification of optimal drilling sites for investigation and sampling by the Rover's 2-m drill. WISDOM will help ensure the safety and success of drilling operations by identification of potential hazards that might interfere with retrieval of subsurface samples

The high-resolution map of Oxia Planum, Mars; the landing site of the ExoMars Rosalind Franklin rover mission

This 1:30,000 scale geological map describes Oxia Planum, Mars, the landing site for the ExoMars Rosalind Franklin rover mission. The map represents our current understanding of bedrock units and their relationships prior to Rosalind Franklin’s exploration of this location. The map details 15 bedrock units organised into 6 groups and 7 textural and surficial units. The bedrock units were identified using visible and near-infrared remote sensing datasets. The objectives of this map are (i) to identify where the most astrobiologically relevant rocks are likely to be found, (ii) to show where hypotheses about their geological context (within Oxia Planum and in the wider geological history of Mars) can be tested, (iii) to inform both the long-term (hundreds of metres to ∼1 km) and the short-term (tens of metres) activity planning for rover exploration, and (iv) to allow the samples analysed by the rover to be interpreted within their regional geological context.The ExoMars Rosalind Franklin Mission is a partnership between ESA and NASA. The Rosalind Franklin Rover has eight instruments in its ‘Pasteur’ Payload, with Principal Investigators from seven countries all of whom we would like to thank for there support of this project. We would like to acknowledge the following funding bodies, people and institutions supporting the lead authors of this work. We thank the UK Space Agency (UK SA) for funding P. Fawdon, on grants; ST/W002736/1, ST/L00643X/1 and ST/R001413/1, MRB on grants; ST/T002913/1, ST/V001965/1, ST/R001383/1, ST/R001413/1, P. Grindrod on grants; ST/L006456/1, ST/R002355/1, ST/V002678/1 and J. Davis on grants ST/K502388/1, ST/R002355/1, ST/V002678/1 through the ongoing Aurora space exploration programme. C. Orgel was supported by the ESA Research Fellowship Program. Alessandro Frigeri: was funded by the Italian Space Agency (ASI) grant ASI-INAF number 2017-412-H.0 (ExoMars/Ma_MISS) and D. Loizeau was funded by the H2020-COMPET-2015 programme (grant 687302), C. Quantin-Nataf was supported by the French space agency CNES, I. Torres was supported by an ESA Young Graduate Traineeship, A. Nass was supported by Helmholtz Metadata Projects (#ZT-I-PF-3-008). We thank NASA and the HiRISE camera team for data collection support throughout the ExoMars landing site selection and charectorisation process. The USGS for the HiRISE DTM data and maintaining the ISIS and SOCET SET DEM workflows. The authors wish to thank the CaSSIS spacecraft and instrument engineering teams. CaSSIS is a project of the University of Bern and funded through the Swiss Space Office via ESA's PRODEX programme. The instrument hardware development was also supported by the Italian Space Agency (ASI) (ASI-INAF agreement no. I/2020-17-HH.0), INAF/Astronomical Observatory of Padova, and the Space Research Center (CBK) in Warsaw. Support from SGF (Budapest), the University of Arizona (Lunar and Planetary Lab.) and NASA are also gratefully acknowledged. Operations support from the UK Space Agency under grant ST/R003025/1 is also acknowledged. This research has made use of the USGS Integrated Software for Imagers and Spectrometers (ISIS) Technical support for setup of the Multi-Mission Geographic Information System for concurrent team mapping was provided by F. Calef (III) and T. Soliman at NASA JPL and S. de Witte at ESA-ESTEC.This work was supported by Agencia Estatal de Investigación [grant number ID2019-107442RB-C32, MDM-2017-0737]; Agenzia Spaziale Italiana [grant number 2017-412-H.0]; Bundesministerium für Wirtschaft und Technologie [grant number 50 QX 2002]; Centre National de la Recherche Scientifique; Centre National d’Etudes Spatiales; Euskal Herriko Unibertsitatea [grant number PES21/88]; Istituto Nazionale di Astrofisica [grant number I/ 060/10/0]; Ministerio de Economía y Competitividad [grant number PID2019-104205GB-C21]; Ministry of Science and Higher Education of the Russian Federation [grant number AAAA-A18-118012290370-6]; National Aeronautics and Space Administration [grant number NNX15AH46G]; Norges Forskningsråd [grant number 223272]; European Union's Horizon 2020 (H2020-COMPET-2015) [grant number 687302 (PTAL)]; Sofja Kovalevskaja Award of the Alexander von Humboldt Foundation; MINECO [grant number PID2019-107442RB-C32]; The Open University [grant number Space Strategic Research Area]; European Union's Horizon 2020 research and innovation programme [grant number 776276]; H2020-COMPET-2015 [grant number 687302]; The Research Council of Norway, Centres of Excellence funding scheme [grant number 223272]; Helmholtz Metadata Projects [grant number ZT-I-PF-3-008]; The Research Council of Norway [grant number 223272]; Swiss Space Office via ESA's PRODEX programme; Ines Torres was supported by an ESA Young Graduate Traineeship; Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung [grant number 200021_197293]; Science and Technology Facilities Council [grant number 1967420]; UK Space Agency [grant number ST/K502388/1, ST/R002355/1, ST/V002678/1]. The ExoMars Rosalind Franklin Mission is a partnership between ESA and NASA. The Rosalind Franklin Rover has eight instruments in its ‘Pasteur’ Payload, with Principal Investigators from seven countries all of whom we would like to thank for there support of this project. We would like to acknowledge the following funding bodies, people and institutions supporting the lead authors of this work. We thank the UK Space Agency (UK SA) for funding P. Fawdon, on grants; ST/W002736/1, ST/L00643X/1 and ST/R001413/1, MRB on grants; ST/T002913/1, ST/V001965/1, ST/R001383/1, ST/R001413/1, P. Grindrod on grants; ST/L006456/1, ST/R002355/1, ST/V002678/1 and J. Davis on grants ST/K502388/1, ST/R002355/1, ST/V002678/1 through the ongoing Aurora space exploration programme. C. Orgel was supported by the ESA Research Fellowship Program. Alessandro Frigeri: was funded by the Italian Space Agency (ASI) grant ASI-INAF number 2017-412-H.0 (ExoMars/Ma_MISS) and D. Loizeau was funded by the H2020-COMPET-2015 programme (grant 687302), C. Quantin-Nataf was supported by the French space agency CNES, I. Torres was supported by an ESA Young Graduate Traineeship, A. Nass was supported by Helmholtz Metadata Projects (#ZT-I-PF-3-008). We thank NASA and the HiRISE camera team for data collection support throughout the ExoMars landing site selection and charectorisation process. The USGS for the HiRISE DTM data and maintaining the ISIS and SOCET SET DEM workflows. The authors wish to thank the CaSSIS spacecraft and instrument engineering teams. CaSSIS is a project of the University of Bern and funded through the Swiss Space Office via ESA's PRODEX programme. The instrument hardware development was also supported by the Italian Space Agency (ASI) (ASI-INAF agreement no. I/2020-17-HH.0), INAF/Astronomical Observatory of Padova, and the Space Research Center (CBK) in Warsaw. Support from SGF (Budapest), the University of Arizona (Lunar and Planetary Lab.) and NASA are also gratefully acknowledged. Operations support from the UK Space Agency under grant ST/R003025/1 is also acknowledged. This research has made use of the USGS Integrated Software for Imagers and Spectrometers (ISIS) Technical support for setup of the Multi-Mission Geographic Information System for concurrent team mapping was provided by F. Calef (III) and T. Soliman at NASA JPL and S. de Witte at ESA-ESTEC.Peer reviewe

The high-resolution map of Oxia Planum, Mars; the landing site of the ExoMars Rosalind Franklin rover mission

This 1:30,000 scale geological map describes Oxia Planum, Mars, the landing site for the ExoMars Rosalind Franklin rover mission. The map represents our current understanding of bedrock units and their relationships prior to Rosalind Franklin’s exploration of this location. The map details 15 bedrock units organised into 6 groups and 7 textural and surficial units. The bedrock units were identified using visible and near-infrared remote sensing datasets. The objectives of this map are (i) to identify where the most astrobiologically relevant rocks are likely to be found, (ii) to show where hypotheses about their geological context (within Oxia Planum and in the wider geological history of Mars) can be tested, (iii) to inform both the long-term (hundreds of metres to ∼1 km) and the short-term (tens of metres) activity planning for rover exploration, and (iv) to allow the samples analysed by the rover to be interpreted within their regional geological context

Performance validation of the ExoMars 2018 WISDOM GPR in ice caves, Austria

International audienceThe WISDOM (Water Ice Subsurface Deposits Observations on Mars) Ground Penetrating Radar has been selected to be part of the ExoMars 2018 exobiological rover mission. A prototype has been tested during the Mars Simulation organized by the Austrian Space Forum in Alpine ice caves in Dachstein, Austria. This campaign provided the opportunity to validate methods developed to process WISDOM’s data in a well-documented environment and to retrieve geometrical and quantitative information about the 3D structure and the electromagnetic properties of the subsurface. We estimate the ice thickness in different locations inside the ice caves, and show that this ice is formed of fine strata with different properties. Data analysis allows reconstructing the bedrock in a 3D environment where a complete survey was performed

On-Site Response Tracking for WISDOM System

International audienceThe WISDOM ground penetrating radar aboard the Rosalind Franklin rover is waiting for its intended launch in 2028 within the ExoMars mission. It will search for Water, Ice, and Subsurface Deposit On Mars (WISDOM) to enhance the knowledge of Oxia Planum on Mars. Meanwhile, the WISDOM team is improving the signal processing, since in general the microwave scattering in the sensing channel is a very complex phenomenon [1]. It is mainly determined by the property of transceiver system (radar), of the wireless channel in the random media and the property of the targets to explore. Regarding the target property, it can be divided into two main factors, namely the geometry/shape and the material properties (frequency-dependent relative permittivity). In practice however, due to the high complexity and sensibility of the random scattering signal tracking and separating of these responses is a challenging task by pre-calibration such that it can deteriorate e.g. the subspace image analysis. With radar systems such as WISDOM, which have a distance of up to several wavelengths between the antenna and the ground, there is furthermore an influence from the environment on the radar coupling, which results in an unknown signal. A reasonable tracking/estimation, especially on-site calibration, of these random signal plays then a major role for the radar technologies in practice and will be outlined in this paper.</div

Radar Subsurface Imaging by Phase Shift Migration Algorithm

In this paper the phase shift migration based Syn- thetic Aperture Radar (SAR) is described and applied on radar imaging for dual polarized ground penetrating radar system (GPR). Conventional techniques for SAR imaging focusing use the matched filter concept and convolve the measurement data with a filter impulse response (convolution kernel) which is modified by the range. In fact, conventional techniques for SAR imaging technique can be considered as ray-tracing based SAR imaging technique. It is an efficient technique to obtain focused radar images, when the medium is homogeneous so that the rays of EM wave propagation can be treated as straight lines. However, in case of layered materials the waves are refracted on the interface between two different materials. In contrast, phase shift migration based SAR imaging technique is through EM field extrapolation by phase shift to obtain the reflected EM intensity and radar imaging of scatterers' reflectivity in the radar illumination area. Although EM wave is refracted on the interface of different materials, the EM wave phase is unchanged. Compared to conventional SAR imaging technique, phase shift migration based SAR imaging approach is more suited to obtain focused radar subsurface imaging for GPR systems. In this paper the phase shift migration approach is applied to experimental data as well as practical measurement data. Meanwhile, a background removal algorithm and a spreading and exponential correcting technique is applied to improve the achievement. The presented focused subsurface and scatters radar imaging results show that phase shift migration based SAR technique is satisfied for radar subsurface imaging and inhomogeneous medium imaging

External calibration of GPR antenna accommodated on a rover

International audienceThis paper describes an external calibration of an antenna system that is used for rover based GPR-Systems. The used antenna system consists of two identical crossed double Vivaldi structures. After the description of the radar system, the electrical properties of the antenna system are characterized. The influence of the rover chassis is shown with the help of some simulated footprints. After explanation of the calibration in detail, it is applied to outdoor measurements

Advance of WISDOM GPR Antenna for ExoMars 2018 Mission

The Experiment "Water Ice and Subsurface Deposit Observations on Mars" (WISDOM) is a Ground Penetrating Radar (GPR) selected to be part of the Pasteur payload on board the rover of European Space Agency's (ESA) ExoMars 2018 mission. The GPR antenna system described in this paper is the consequent progression of former developments [1, 2] incorporating changed requirements and further optimizations. Main constraints are the mass, the temperature range as well as the ultra-wide band demand. The antenna requirements which are to fulfill for this very specific GPR application are described here. Furthermore, it is given an overview about the lightweight design and its realization. Simulated and measured antenna performance is compared in this paper

Framework for the Generation of Large Datasets of Synthetic RADAR Soundings of the Martian Subsurface

International audienceEssential for the successful training and application of AI tools to the automated processing of planetary RADAR soundings is the availability of sufficiently labeled and annotated data for the specific instruments and solar system bodies. For data of planetary RADAR sounders, no ground truth is typically available, resulting in labels and annotations derived from models of observations. A different approach is to generate synthetic data by simulation of the RADAR sounding process, including all relevant instrument characteristics and models of the surface and subsurface of the sounded solar system body. In this context, the aim of such automated processing approaches is to annotate subsurface signatures, e.g., hyperbolas, that could indicate point-like scatterers, which are of interest for a permittivity estimation. To simplify the generation of many RADAR datasets for the WISDOM instrument, a payload of the ExoMars Rosalind Franklin rover, scheduled for 2022, we have developed a framework to efficiently create random variations of models of Oxia Planums subsurface. Using this framework, we aim to generate sufficient data for the automatic processing of the WISDOM measurements and the extraction of subsurface features. Furthermore, the framework can be applied to other missions and RADAR sounders and extended to integrate synthetic results from other instruments. In this presentation, we demonstrate initial results generated with the framework, as well as introduce the general workflow and steps necessary to parametrize the model generation

Ultra light-weight antenna system for full polarimetric GPR applications

International audienceThe motivation to develop an ultra light-weight antenna system was driven by a space borne radar application. The experiment ldquowater ice and subsurface deposit observations on Marsrdquo (WISDOM) is a ground penetrating radar (GPR) selected to be part of the Pasteur payload on board the rover of the ExoMars mission. Among the Pasteur panoramic instruments on the ExoMars rover, only WISDOM can provide a view of the subsurface structure. WISDOM is the first GPR on a planetary rover. It has been designed to characterize the shallow subsurface structure of Mars. WISDOM will for the first time give access to the geological structure, electromagnetic nature, and, possibly, hydrological state of the shallow subsurface by retrieving the layering and properties of the buried reflectors. It will address important scientific questions regarding the planet's present state and past evolution. The measured data will also be used to determine the most promising locations to obtain underground samples with the drilling system mounted on board the rover. The instrument's objective is to get high-resolution measurements down to 2 m depth in the Martian crust. The radar is a gated step frequency system covering a frequency range from 500 MHz to 3 GHz. The radar is fully polarimetric and makes use of an ultra wideband antenna system based on Vivaldi antenna elements. The paper describes antenna requirements to fulfil for this very specific GPR application and it gives an overview about the light-weight design and its realization. Simulated and measured antenna performance is compared in this paper. Test measurements were performed in permafrost regions on earth