After their formation, the Earth and Mars might have been very similar but today, contrary to the Earth, Mars is a very dry planet without plate tectonics and with a tenuous atmosphere of CO2 mainly. Understanding the structure of the interior of Mars is very important to provide new information about the prime structure and evolution of this planet. As deep planetary interiors are inaccessible to direct observation, the most effective way to explore them is through geophysics. The LaRa (ExoMars mission) and RISE (InSight mission) instruments are both X-band transponders designed to determine Mars’ Orientation and rotation parameters (MOP) by analyzing the Doppler shift of the two-way radio signals between a lander on Mars and ground stations on Earth. The targeted MOP are the variations of Mars’ rotation rate or length-of-day (LOD), the variations of the orientation of the rotation axis in space (precession and nutations) and the polar motion. These data will provide information on the interior structure (such as the state, size and composition of the core) and on the atmosphere of Mars.

This thesis work aims to provide support in the analysis of RISE and LaRa data by performing numerical simulations of Doppler measurements. The objectives are to infer the requirements for future LaRa operations, to assess the influence of non-modelled effects on the MOP and to provide optimal analysis strategies, as well as for the processing and interpretation of the RISE and LaRa data, for the processing of the noise and the selection of the most suitable parameters set to estimate.

Among the main results, this work provides several recommendations concerning the technical and operational aspects of a radioscience experiment on a lander. In particular, the regular alternation of the lander tracking between east and west is mandatory to ensure a better fitting of the MOP. Moreover, the benefit of having LaRa after RISE has been demonstrated for the determination of nutation and polar motion parameters. According to our simulations, combining the data provided by both instruments improve the expected knowledge about the core.