The radioscience LaRa instrument onboard ExoMars 2020 to investigate the rotation and interior of mars

Dehant, Véronique [UCL] Le Maistre, Sébastien [Royal Observatory of Belgium, Brussels, 3 Avenue Circulaire, B1180, Brussels, Belgium] Baland, Rose-Marie [Royal Observatory of Belgium, Brussels, 3 Avenue Circulaire, B1180, Brussels, Belgium] Bergeot, Nicolas [Royal Observatory of Belgium, Brussels, 3 Avenue Circulaire, B1180, Brussels, Belgium] Karatekin, Özgür [Royal Observatory of Belgium, Brussels, 3 Avenue Circulaire, B1180, Brussels, Belgium] Péters, Marie-Julie [Royal Observatory of Belgium, Brussels, 3 Avenue Circulaire, B1180, Brussels, Belgium] Rivoldini, Attilio [Royal Observatory of Belgium, Brussels, 3 Avenue Circulaire, B1180, Brussels, Belgium] Ruiz Lozano, Luca [Royal Observatory of Belgium, Brussels, 3 Avenue Circulaire, B1180, Brussels, Belgium] Temel, Orkun [Royal Observatory of Belgium, Brussels, 3 Avenue Circulaire, B1180, Brussels, Belgium] Van Hoolst, Tim [Royal Observatory of Belgium, Brussels, 3 Avenue Circulaire, B1180, Brussels, Belgium] Yseboodt, Marie [Royal Observatory of Belgium, Brussels, 3 Avenue Circulaire, B1180, Brussels, Belgium] Mitrovic, Michel [Royal Observatory of Belgium, Brussels, 3 Avenue Circulaire, B1180, Brussels, Belgium] Kosov, Alexander S. [IKI - Space Research Institute of Russian Academy of Sciences, Moscow, Russia] Valenta, Vaclav [European Space Research and Technology Centre (ESTEC), ESA, the Netherlands] Thomassen, Lieven [AntwerpSpace, OHB Company, Belgium] Karki, Sumit [UCL] Al Khalifeh, Khaldoun [UCL] Craeye, Christophe [UCL] Gurvits, Leonid I. [JIVE–Joint Institute for VLBI ERIC (European Research Infrastructure Consortium), the Netherlands] Marty, Jean-Charles [Observatoire Midi-Pyrenees, GRGS, CNES, France] Asmar, Sami W. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA] Folkner, William M. [Jet Propulsion Laboratory, California Institute of Technology, Pasadena, USA] et al.[show all]

LaRa (Lander Radioscience) is an experiment on the ExoMars 2020 mission that uses the Doppler shift on the radio link due to the motion of the ExoMars platform tiedto the surface of Mars with respect to the Earth ground stations (e.g. the deep space network stations of NASA), in order to precisely measure the relative velocity of thelander on Mars with respect to the Earth. The LaRa measurements shall improve the understanding of the structure and processes in the deep interior of Mars byobtaining the rotation and orientation of Mars with a better precision compared to the previous missions. In this paper, we provide the analysis done until now for thebest realization of these objectives. We explain the geophysical observation that will be reached with LaRa (Length-of-day variations, precession, nutation, andpossibly polar motion). We develop the experiment set up, which includes the ground stations on Earth (so-called ground segment). We describe the instrument, i.e.the transponder and its three antennas. We further detail the link budget and the expected noise level that will be reached. Finally, we detail the expected results,which encompasses the explanation of how we shall determine Mars' orientation parameters, and the way we shall deduce Mars' interior structure and Mars’at-mosphere from them. Lastly, we explain briefly how we will be able to determine the Surface platform position.