Kosov, Alexander ; Le Maistre, Sébastien ; Dehant, Véronique ; Baland, Rose-Marie ; Karatekin, Ozgur ; Mitrovic, Michel ; Péters, Marie-Julie ; Rivoldini, Attilio ; Van Hoolst, Tim ; Van Hove, Bart ; Yseboodt, Marie

Poster presented at Ninth Moscow International Solar System Symposium (9M-S3), Space Research Institute(IKI), Moscow, Russia. on 2018-10-08

Abstract: The LaRa experiment is designed to obtain coherent two-way Doppler meas-urements from the radio link between the 2020 ExoMars lander (the Sur-face Platform, SP) and the Earth over at least one Martian year. The Doppler measurements will be used to observe the orientation and rotation of Mars in space (precession, nutations, and length-of-day variations), as well as polar motion. The ultimate objective is to obtain information on the Martian inte-rior and on the sublimation/condensation cycle of atmospheric CO2. Rota-tional variations will allow us to constrain the moment of inertia of the entire planet, including its mantle and core, the moment of inertia of the core, and seasonal mass transfer between the atmosphere and the ice caps.Besides, LaRa could allow to accurately determine the position of the SP within a very short time after the starting of operations. An early estimate of the lander location will certainly improve the quality of the science anal-ysis (for instance by making easier the recognition of the geological features seen on the lander’s pictures) and allow high-resolution cameras from space-craft like MRO to correctly target the lander. The classical technique using Delta DOR measurements for obtaining the SP position has an accuracy in the plane of sky of 200-900m (depending on the Earth-Mars distance), while our estimation combining LaRa Doppler data and local terrain maps is about 10 m. Such an early precise estimate of the lander location will also certainly improve the quality of the science analysis.

Keyword(s): LaRa ; Mars ; ExoMars 2020
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