Dottorato in INGEGNERIA AERONAUTICA E SPAZIALE

Titolo della tesi: Analysis of deep space radio science experiments on-board BepiColombo and JUICE missions

This thesis focuses on the radio science experiments on-board ESA-JAXA’s Bepi- Colombo mission to Mercury and ESA’s JUICE mission to the Jupiter’s moons. The first in-flight data from the Mercury Orbiter Radio-science Experiment (MORE) Ka-band tranposnder (KaT) of BepiColombo were acquired in May 2019 from ESA ESTRACK DSA-3 station, located in Malargüe Argentina. The analysis shows an unprecedented accuracy of less than 1 cm for range measurements (PN range at 24 Mcps) and an excellent accuracy for range-rate observable, 0.01 mm/s at 60 s of integration time. Data from 20 to 24 May 2019 were combined in a multi-pass analysis to test the link stability on a longer timescale. The results confirm the noise level observed with the single-pass analysis and provide a preliminary indication that the MORE PN ranging system at 24 Mcps is compatible with the realization of an absolute measurement, where the need to introduce range biases in the orbital fit is much more limited than in the past. An analysis of the Gravity and Geophysics of Jupiter and the Galilean Moons (3GM) experiment is executed under different mission scenarios to identify the performances of the scientific measurements. The Europa phase comprises of only two flybys and will let us to verify the hydro-static equilibrium hypothesis, J2/C22 = 10/3, at the level of 1%. The analysis of the 12 flyby of Callisto highlighted some issues with the current mission design. The Love number k2, modelling the gravitational response to eccentricity-driven, time-variable gravity gradient from Jupiter, will be hardly constrained with the current mean anomaly distribution of the Callisto encounters. In an optimistic case, the k2 Love number can be recovered with an accuracy of 0.083, higher than the scientific requirement of 0.06. The backup trajectory 230la provides a significant improvement in the estimation of the tidal Love number k2, allowing us to obtain k2 = 0.050, under a more realistic mission scenario. The simulations of the 4-month circular orbit at 500 km of altitude reveal that the Ganymede’s gravity field can be determined up to degree and order 40, depending on the magnitude of the gravity spectrum. The Love number k2 is determined with an accuracy of k2  10−4. The obliquity, ', and the libration at orbital period, , can be retrieved with a level of uncertainty of 1 and 2 μrad, respectively.