Phd in AERONAUTICS AND SPACE ENGINEERING

Thesis title: Characterization of Static and Time-varying Gravity Anomalies on Planetary Bodies with Radio Science Data

The study of planetary gravity fields provides fundamental insights into the internal structure, mass distribution, and dynamic evolution of celestial bodies. This dissertation merges advanced precise orbit determination techniques with refined geodetic models, offering a comprehensive investigation into static and time-varying gravity anomalies of planetary bodies. A detailed analysis of BepiColombo’s Venus and Mercury flybys was conducted, leveraging a multi-arc precise orbit determination approach that integrated spacecraft radio science and accelerometer data with the entire MESSENGER mission’s radio-tracking measurements. The analysis validated onboard accelerometer data and semi-empirical models of non-conservative forces acting on BepiColombo. This methodology led to a new estimate of the gravity field of Mercury and an improved characterization of gravity anomalies across the Beethoven impact basin region, enhancing the correlation with topography and enabling further investigations into the lithospheric properties of the planet. The investigation then extended to the seasonal variations of the Martian gravity field, driven by CO2 mass exchange between the polar caps and the atmosphere. A mascon-based approach, combined with remote-sensing observations, was developed to quantify temporal variations in the mass of the seasonal polar caps, leveraging multi-year Doppler tracking data from the Mars Reconnaissance Orbiter. A comparative assessment of atmospheric models was performed, evaluating the density behavior of MarsGram2010 and the Mars Climate Database across different Martian years. The results provided accurate estimates of the mass evolution of the northern polar cap, revealing a stable trend during summer, which aligns with general circulation model predictions and remote-sensing observations. The methodologies developed in this study are designed for broad applicability, extending beyond the specific cases of Mercury and Mars to the analysis of radio science data from any planetary mission.