Abstract | The Mercury Orbiter Radioscience Experiment (MORE) onboard the BepiColombo mission was designed to provide an accurate estimation of the gravity field and the rotational state of Mercury and to perform fundamental physics tests during the cruise phase and the orbital phase of the mission. The Mercury Planetary Orbiter (MPO) is equipped with a state-of-the-art radio tracking system composed of the MORE’s Ka-band Transponder (KaT), which enables Ka-band Doppler and Pseudo-Noise (PN) range data at 24 Mcps, and the Deep Space Transponder (DST) which enables the X/X and X/Ka Doppler and range data at 3 Mcps. The 5-way link configuration allows us to obtain range-rate and range coherent two-way measurements respectively accurate to 0.003 mm/s (at 1000 s integration time) and a ~5 cm (after a few seconds of integration time), nearly at all solar elongation angles. The radiometric data will permit obtaining a precise reconstruction of the spacecraft orbit and estimating the spherical harmonic coefficients of the Hermean gravity field at least up to degree 45 (Imperi et al. 2019), the tide, and the rotational parameters (right ascension and declination of the pole and physical librations in longitude). The BepiColombo low eccentric orbit will provide global and uniform coverage of the planet, improving the MESSENGER gravity measurements, especially in the southern hemisphere. A full numerical simulation of the radio science orbit determination process has been carried out including the onboard Italian Spring Accelerometer (ISA) noise model. In this work, we report on the results of numerical simulations aiming at a realistic assessment of the attainable accuracy in the determination of the gravity field and the rotation of Mercury and focusing on the geophysical implications. The benefits of an extended mission will be highlighted. |
