Comet Interceptor: Optimisation of Quasi-Ballistic Departure Opportunities by Means of a Lunar Swing-by

Abstract

As part of the Cosmic Vision Programme, Comet Interceptor was selected in 2019 as a Fast-track mission programmed to be launched in 2028 together with the Ariel M4 mission. The objective of the mission is the interception of a pristine comet on its way through the solar system. To accomplish this task the spacecraft will be placed in a quasi-Halo orbit around the L_2 Libration Point where it will stay until a suitable target is identified. At this point the spacecraft begins its journey to the comet by departing from the parking orbit and escaping the Earth’s gravitational field.

The aim of this thesis is the analysis of the first section of this journey, i.e., from the detection of the comet to the moment of escape. The analysis is performed assuming the validity of the Planar Circular Restricted Three-Body Problem (PCR3BP) and focuses on the evaluation of the expected value of the escape velocity with respect to the Earth. Initially the trajectory is computed by simply propagating a set of initial conditions, however, in order to optimise the escape conditions, a lunar flyby is introduced to alter the trajectory achieving higher v∞.

Via a Monte Carlo Simulation it is demonstrated that optimal flybys can be systematically targeted and exploited under different initial conditions, leading generally to a substantial increase in escape velocity potentially reducing the Δv budget that needs to be provided by the spacecraft. Furthermore, it was proven that for some of the transfers also a reduction of the time of flight can be achieved reducing the required notice time, and thus increasing the success rate of the mission.

The obtained analysis serve as a starting point for the analysis of the interplanetary leg of Comet Interceptor. Moreover, the developed methodology can be used for the analysis of trajectories involving multiple lunar flybys.