I have been working recently on the integration of a new starshade class into EXOSIMS which can simulate starshade motion with higher fidelity. The humbly named SotoStarshade class integrates the circular restricted three body equations of motion to find the states of the occulter as it dances around a telescope on an L2 halo orbit in a rotating frame. As of now, it can solve boundary value problems to determine slew trajectories: while the telescope slews to a new target the occulter flies over to align with the telescope’s line of sight. This slew time can be varied accordingly to reduce the amount of fuel used in the impulsive maneuvers or can even be minimized given fuel constraints. With this new starshade class, trajectories can be generated throughout the mission.
The video shown above shows the simulation of the starshade motion about L2 as the telescope slews to view new targets. Slew times are set to 20 days for every target and the station-keeping motion is not shown. New methods will be introduced in the near future that can interpolate the fuel costs for quick calculations and vary the slew times to sync with targets coming in and out of the Sun (and other planetary) keepout zones in the sky; a new scheduler will also be added to the SurveySimulation module.