On-Orbit Servicing System Architectures for Proliferated Low-Earth-Orbit Constellations

On-orbit servicing (OOS) presents new opportunities for refueling, inspection, repair, maintenance, and upgrade of spacecraft (s/c). OOS missions for s/c in a geostationary orbit (GEO) are currently underway. However, there are currently no plans for OOS of low-Earth-orbit (LEO) s/c, aside from technology demonstrations, because of their shorter design life and lower cost. Designing OOS systems for LEO constellations differs from that of GEO-based systems; this difference is attributed to LEO's proliferation of satellites, environmental effects (J2 nodal precession, drag), and different constellation patterns. Satellite constellations in LEO are becoming more distributed due to increased access, distributed risk, flexibility, and cost. OOS of s/c may enable the reduction of requirements on subsystems such as safety and the need for redundancy. These requirement reductions will enable lower risks, lower costs, and increased system resilience. This paper analyzes the benefits of OOS in proliferated LEO constellations. Several OOS system architectures are modeled in various scenarios, and we will evaluate the utility tradespace in which OOS is beneficial. OOS provides higher utility over the comparative alternative of using spare satellites in some scenarios. The utility of OOS provides even greater utility when accepting higher failure rates of satellites, which can be mitigated by an OOS system compared to the comparative alternative of orbital spares.