Centralized visual based navigation and control of a swarm of satellites for on-orbit servicing

In the framework of on-orbit proximity operations, small satellites represent an appealing solution in terms of costs, effectiveness and realization, but show intrinsic power, mass and computation limitations that could be overcome if cooperation among many spacecraft is considered. In this research, a swarm of small satellites (called “Children S/C″), deployed from a larger platform (called “Mother S/C″), is employed in the inspection of a damaged spacecraft, which cannot be directly approached by the Mother S/C for safety reasons. The navigation process is delegated to the Mother S/C, that is equipped with a passive camera. A navigation algorithm runs on the Mother S/C, which identifies and tracks the Children S/C framed in the scene, even though false matches (i.e., incorrect tracking of a given child) could happen. The navigation algorithm is made robust through the generation at each time step of a propagated virtual image (based on the previous estimate of the swarm state) which is compared to the acquired image for the correct identification of each child. When the relative position estimates reach a satisfactory accuracy, the Mother S/C communicates to the Children S/C their current state and an optimal impulsive control strategy can be implemented to make the swarm fulfill the required inspection task. Simulations are carried out in a purposely developed software environment, in which images of rendered CAD models are acquired and processed to have a realistic validation of the estimation algorithm, showing satisfactory performance and robustness for the overall mission accomplishment.