Design and Validation of Ultra Low Thrust Transfers to the Sun-Earth Saddle Point with Application to LISA PathFinder Mission Extension

In this paper we present methods and concepts to design and validate highly nonlinear orbits characterized by ultra low control. These features are met when flying through the Saddle Points, which are location in the Solar System when gravitational accelerations balance. Trajectory optimization is embedded into high-fidelity environments, where accurate description of the spacecraft natural and controlled motion is achieved. Orbit determination and navigation analysis rely on high-fidelity models for both the space and ground segments assets as well. Tools have been developed and applied to the case of the possible mission extension of Lisa Pathfinder.