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

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The inverse scattering problem described in this paper is part of the quasi-tomographic comet nucleus sounding experiment CONSERT of the comet-mission Rosetta. This part of the experiment is based on the utilization of radiation coupling effects between the CONSERT antenna system on the RosettaLander and the subsurface structure of the comet nucleus in the vicinity of the Lander. The scientific aim of this part of CONSERT is the reconstruction of the subsurface structure at the landing site, especially in view of the still open question: "Is a comet nucleus surround by a dust layer or not?". To solve this inverse scattering problem the line-of-sight link between Rosetta Orbiter and Lander will be used to measure the back lobes of the CONSERT Lander antenna with high angular resolution.

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