Diagnostic of the dayside ionosphere of Mars using the Total Electron Content measurement by the NEIGE/Netlander experiment: An assessment study

摘要

The NEtlander Ionosphere and Geodesy Experiment (NEIGE) of the Netlander mission to Mars will measure Doppler shifts affecting the radio links between ground stations and an orbiter. The experiment has two complementary scientific objectives which are the monitoring of the structure and dynamics of the ionosphere of Mars and the precise determination of Mars orientation parameters. The horizontal variation of the Total Electron Content (TEC) of the ionosphere will be derived from the so-called "geometric-free" combination of the Doppler shifts which affect radio links at two frequencies (in the UHF and S bands) between the Netlander microstations on the Mars surface and the data-relay orbiter. We describe a new method for retrieving the horizontal profile of the absolute value of the TEC. Simulations have allowed to evaluate the precision in the determination of the TEC using this method. We show that the daytime TEC can be retrieved with a precision of 5 x 10~(13) m~(-2) for a nominal accuracy of 0, 1 mm/s on the orbital pseudo-velocity, which represents a relative precision of a few percent. A preliminary analysis of the sensitivity of the TEC to the physical parameters which control the ionosphere has been performed. For this purpose, we have used a new one-dimensional ionospheric model based on the solution of coupled kinetic, fluid and MHD equations. This model describes the suprathermal electron component, the thermal plasma component as well as the induced horizontal magnetic field. The code which provides the vertical electron density profile has been used to study the variation of the TEC with the solar zenith angle and with the induced magnetic field at the top of the ionosphere, In particular, we show that NEIGE will allow to diagnose the penetration into the daytime ionosphere of an induced magnetic field.