Thesis title: The effect of exospheric and atmospheric drag on the orbit determination of planetary probes: The JUICE and Cassini cases
Orbit determination is the process in which we combine spacecraft observations such as Doppler measurements, together with knowledge of the spacecraft dynamical model to determine the spacecraft's position and velocity. We can also use this process to improve dynamical force parameters that affect the spacecraft's trajectory, such as gravity field coefficients or atmospheric drag. This Doctoral Thesis reports on the effect of the acceleration due to drag experienced by two planetary probes in the presence of an atmosphere or exosphere: Cassini, the mission to the Saturn system which ended in 2017, and JUICE, a mission to study Jupiter's icy satellites which is planned for launch in 2022. The goals of this thesis are: for Cassini, to infer a density profile for Saturn's upper atmosphere using data taken during the final few moments of its plunge into Saturn; for JUICE, to incorporate a model describing Ganymede's exosphere into the orbit determination software to determine whether the model can be improved and if the onboard accelerometer will be sensitive to the drag acceleration during the GCO500 phase --- a 4-month circular orbit around the moon.