Cluster flight algorithms for disaggregated satellites

In disaggregated satellites, the functional capabilities of a single monolithic satellite are distributed among multiple free-flying, wirelessly communicating modules. One of the main challenges associated with disaggregated satellites is cluster flight, i.e., keeping the modules within a bounded distance, typically less than 100 km, for the entire mission lifetime. This paper presents a methodological development of cluster flight algorithms for disaggregated satellite systems in low Earth orbits. To obtain distance-bounded relative motion a new constraint on the initial conditions of the modules is developed. A concomitant analytical bound on the relative distance between the modules is proven based on a design model assuming time invariance of the environmental perturbations. It is then shown that if the actual astrodynamical model includes other possible time-varying effects, mild drifts between the modules are obtained. Furthermore, this paper presents a detailed impulsive cluster establishment and cluster-keeping algorithm for tracking a given nominal orbit, whose characteristics satisfy the previously developed no-drift constraint. This algorithm provides fuel balancing among the maneuvering modules, as well as the minimization of the total fuel consumption, while guaranteeing a collision-free operation. Numerical simulations using representative astrodynamical models are used to validate the analysis.