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

Abstract

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 tied to 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 the lander 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 by obtaining 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 the best realization of these objectives. We explain the geophysical observation that will be reached with LaRa (Length-of-day variations, precession, nutation, and possibly 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' atmosphere from them. Lastly, we explain briefly how we will be able to determine the Surface platform position.

Retrieving Doppler Frequency via Local Correlation Method of Segmented Modeling

“…Mars exploration is one of the main objectives of international space programs [29]. It is helpful to study Martian sciences such as Martian internal structure by radio measurements [30][31][32][33]. Tianwen-1 is the first Chinese deep probe to Mars for Martian science research, which was launched on 23 July 2020 [34].…”

MoMo: a new empirical model of the Mars ionospheric total electron content based on Mars Express MARSIS data

“…8). The transmitting/receiving antennas on Earth (or on-board a Mars orbiting spacecraft) are assumed to be at different elevation angles seen from the asset: 20°and 55°w hich correspond to the typical elevation range for present and future radio-science operation of RISE (Folkner et al, 2018) and LaRa (Dehant et al, 2019). We also consider an elevation angle of 90°(i.e., at the zenith of the asset).…”

“…The lander signal in X-band is routinely tracked from Earth, with the goal of measuring the rotational movements of the red planet, in order to study its deep interior. A very similar and complementary radio-science experiment called LaRa (Lander Radio science, Dehant et al, 2009Dehant et al, , 2011Dehant et al, , 2019, was also designed to refine the rotation model of Mars and to further constrain its interior. LaRa is part of the scientific payload of the Russian surface platform of the Planetary Space Weather ESA-Roscosmos ExoMars 2020 mission.…”

High spectral resolution multi-tone Spacecraft Doppler tracking software: Algorithms and implementations

“…In these operations, a large antenna transmits a tone to the target of interest, while the receiver antenna(s) observes the bounced echo. The technique has been successfully applied to determine the spin states of asteroids Busch et al (2010) and surveying the space debris with VLBI technology Yajima et al (2007); Montebugnoli et al (2010). In 2021, we have demonstrated the capability of the Hobart and Katherine 12-metre antennas for tracking the echo reflected by a large space vehicle.…”