Research Article

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

¹ Solar-Terrestrial Centre of Excellence (STCE), Space Pole, 1180 Brussels, Belgium
² Royal Observatory of Belgium Brussels, 1180 Uccle, Belgium
³ Earth and Climate, Université Catholique de Louvain, 1348 Louvain-la-Neuve, Belgium
⁴ European Space Agency, ESTEC-Scientific Support Office, ESTEC, 2201 AZ Noordwijk, The Netherlands
⁵ Institut de Recherche en Astrophysique et Planétologie (IRAP), 31400 Toulouse, France
⁶ Université Grenoble Alpes, CNRS, CNES, IPAG, 38400 Grenoble, France
⁷ Space Research Centre, PAS, 00 716 Warsaw, Poland
⁸ Rheinisches Institut für Umweltforschung an der Universität zu Köln, Abt. Planetenforschung, 50931 Köln, Germany

^* Corresponding author: nicolas.bergeot@oma.be

Received: 27 February 2019
Accepted: 9 September 2019

Abstract

Aims: Several scientific landers and rovers have reached the Martian surface since the 1970s. Communication between the asset (i.e., lander or rover) and Mars orbiters or Earth antennas uses radio signals in UHF to X-band frequencies passing through the Mars’ ionosphere. It is consequently necessary to take into account electron density variation in the Mars’ ionosphere to correct the refraction of the signal transmitted. Methods: We developed a new empirical model of the Mars’ ionosphere called MoMo. It is based on the large database of Total Electron Content (TEC) derived from the subsurface mode of the Mars Express MARSIS radar. The model provides vertical TEC as a function of solar zenith angle, solar activity, solar longitude and location. For validation, the model is compared with Mars Express radio occultation data as well as with the numerical model IPIM (IRAP Plasmasphere-Ionosphere Model). Results: We discussed the output of the model in terms of climatology behaviour of the Mars’ ionosphere. The output of MoMo is then uses to quantify the impact of the Martian ionosphere for radio-science experiments. From our results, the effect is of the order of 10⁻³ mm s⁻¹ in Doppler observables especially around sunrise and sunset. Consequently, this new model could be used to support the data analysis of any radio-science experiment and especially for present InSight RISE and futur ExoMars LARA instruments aiming at better understand the deep-interior of Mars.