Autonomous FSM Architecture for Commissioning and Differential Drag Control in CubeSat Formations

The operational success of inter-satellite laser link (ISL) missions in CubeSat constellations depends on the strict management of conflicting requirements: energy harvesting, high-precision payload targeting, and orbital maintenance. This paper presents an automated onboard mission logic designed to manage the relative distance of a two-satellite 6U in formation flight (ranging from 100 km to 1000 km) using differential drag as the sole propellantless maneuvering mechanism.

The main contribution is a deterministic decision-making framework based on a finite-state machine (FSM) that governs transitions between operational modes of the ADCS. These modes, including maximum and minimum drag, ground station tracking, and high-precision laser pointing, are prioritized to modulate the ballistic coefficient between minimum and maximum drag while respecting mission constraints. To ensure mission feasibility, the logic incorporates experimentally derived power and consumption profiles from laboratory characterization of satellite subsystems, while maintaining confidentiality regarding specific hardware components.

The proposed logic is validated using Basilisk, an open-source high-fidelity simulator, incorporating gravitational perturbations and a facet-based aerodynamic model. The results on the first stage of the orbit simulation demonstrate that this drag-based differential logic can achieve a relative drift greater than 400 km per month while maintaining energy balance for operation. In addition, it allows quantification of approximate ballistic coefficients in early stages. Finally, we discuss the potential of parallel learning algorithms to augment the FSM, identifying environmental clusters and predicting energy trends to further optimize deterministic transitions under realistic operational constraints.