MaRS: Mars express orbiter radio science

Citation

Hagermann A, Patzold M & Neubauer FM (2004) MaRS: Mars express orbiter radio science. In: Wilson A (ed.) Mars Express: The Scientific Payload. European Space Agency Special Publication (ESA SP), 1240. Noordwijk, The Netherlans: ESA Publications, pp. 141-163. https://www.esa.int/esapub/sp/sp1240/sp1240web.pdf

Abstract
The Mars Express Orbiter Radio Science (MaRS) experiment will employ radio occultation to (i) sound the neutral martian atmosphere to derive vertical density, pressure and temperature profiles as functions of height to resolutions better than 100 m, (ii) sound the ionosphere to derive vertical ionospheric electron density profiles and a description of the ionosphere through its diurnal and seasonal variations with solar wind conditions; MaRS will also (iii) determine the dielectric and scattering properties of the martian surface in target areas by a bistatic radar experiment, (iv) determine gravity anomalies for the investigation of the structure and evolution of the martian crust and lithosphere in conjunction with observations of the High Resolution Stereo Camera as a base for 3D topography, and (v) sound the solar corona during the superior conjunction of Mars with the Sun. The radio carrier links of the spacecraft Telemetry, Tracking and Command subsystem between the Orbiter and Earth will be used for these investigations. Simultaneous and coherent dual-frequency downlinks at X-band (8.4 GHz) and S-band (2.3 GHz) via the High Gain Antenna will permit separation of contributions from the classical Doppler shift and the dispersive media effects caused by the motion of the spacecraft with respect to the Earth and the propagation of the signals through the dispersive media, respectively. The investigation relies on the observation of the phase, amplitude, polarisation and propagation times of radio signals transmitted from the spacecraft and received with antennas on Earth. The radio signals are affected by the medium through which they propagate (atmospheres, ionospheres, interplanetary medium, solar corona), by the gravitational influence of the planet on the spacecraft and, finally, by the performances of the various systems aboard the spacecraft and on Earth.