Efficient Information Routing for Constellations with Satellite Clusters via Static Digraph

Inter-satellite routing is key to enabling low-latency global connectivity in satellite constellations. Traditional models based on fixed topologies or discrete-time snapshots often overlook the geometric and temporal complexity of orbital motion, especially in sparse or heterogeneous systems. We introduce an event-based graph framework that captures all possible data exchanges within a constellation over a given time horizon. Each node represents a communication event—a finite interval during which one or more satellites can exchange data—while directed edges connect events that can be sequentially linked through shared satellites and overlapping time. The resulting structure is a static directed graph encoding all feasible routing paths based solely on mutual visibility. This compact formulation avoids redundancy typical of time-expanded graphs and naturally accommodates both permanent and temporary clusters, representing continuous or intermittent multi-satellite connectivity. Routing is performed on the event digraph using standard algorithms with latency- and hop-based metrics. Tests on LEO constellations demonstrate that the method efficiently identifies optimal paths and reveals key trade-offs between delay, hop count, and connectivity density, offering a scalable tool for constellation-level routing analysis.