Orbit/Attitude Control for Rendezvous and Docking at the Herschel Space Observatory

In situ resource utilization (ISRU) will be the key for the success of many future space missions which are especially time or cost demanding. This is particularly true for the next Moon settlement mankind has decided to establish, and even further, for Mars colonization. Focusing on Moon operations, this paper presents a study carried out to assess the benefits of on-orbit servicing (OOS) exploiting lunar resources for the resupply of the Herschel Space Observatory (HSO). Herschel ended its operations in 2013 as a consequence of the depletion of its coolant, therefore an experimental mission has been envisaged to refill it. An adapted cargo spacecraft (s/c), employed in lunar gateway operations, will be supposed to depart from the Moon and reach Herschel for the resupply. Trajectory design and optimization for rendezvous, as well as attitude control and a methodology to simplify the dynamics equations through linearization, are the topics addressed in this study in order to obtain some preliminary data on the feasibility of these kind of missions. The results found list different trajectories that could be taken on for the mission, their \(\Delta\)V cost and time of flight (ToF) and show the advantage of relying on simplified dynamics for the calculations. Moreover, it is presented the methodology used to approach the observatory during rendezvous (RdV) while ensuring minimum thrusting errors of the cargo spacecraft and a continuous visibility of the space observatory. The conclusion displays some ideas on how the next studies for the mission could be carried on.