A goal-oriented guidance approach for binary asteroids exploration

Operations in proximity of minor bodies demands high levels of autonomy to achieve cost-effective safe and reliable solutions. Autonomous trajectory and operations planning capability plays a pivotal role in this. A goal-oriented guidance strategy for on-board implementation is presented in this paper to achieve high level mission objectives with impulsive control capability. The methodology is based on abstract reachability analysis performed on the control domain combining model predictive control theory with artificial potential fields algorithms. The formulation of the optimization problem in a general and flexible way allows to target different goals while being compliant with an arbitrary number of mission constraints. In particular, two main contributions to the field are proposed in this work: a way of embedding non-uniform observation constraints in the formulation to deal with challenging illumination conditions, and the inclusion of specific operational constraints to be compliant both with ground operations and on-board replanning. The methodology is applied to the Milani mission, one of the two Hera’s CubeSats, targeting a global coverage of the main attractor, Didymos, and detailed observations of specific features on the secondary asteroid, Dimorphos. The authors, being involved in the mission analysis, image processing, and GNC design of the platform, believe that this methodology also represents a viable tool for efficiently generating flight dynamics references during operations. Different metrics are investigated to achieve mission objectives leading to four application scenarios that are discussed in this work. Results are compared in terms of computational cost, convergence properties and efficiency. These results represent a step forward in enabling autonomous guidance capability for CubeSats proximity operations.