Constrained guidance for spacecraft proximity operations under electrostatic perturbations

Electrostatic perturbations can have significant effects during proximity operations in high earth orbits, with torques achieving levels over 5 mN-m during severe charging events. These torques can impart significant rotational rates to uncontrolled bodies, such as debris or servicing clients, during rendezvous and proximity operations. A sub optimal, but deterministic and computationally efficient, sampling-based method to minimize the impact of these torques during rendezvous is presented here, combining prior innovations in rapidly computing the electrostatic torque between bodies and in determining the electrostatic potential on objects remotely. This method is applied to a simulated servicing scenario, and found to reduce the accumulated rotational rates of the target by over 50%, yielding significant improvements in control effort, and potential improvements in safety. The method can also be applied to position the servicer to impart a desired torque on the target, allowing it to counteract the effects of SRP or potentially reduce the rotational rate of a debris object prior to grappling.