A Three-Phase Progressive Multi-Beam Scheduling Algorithm for Large-Scale LEO Constellation TT&C Operations

Abstract

The multi-beam tracking, telemetry, and command (TT&C) scheduling problem for large-scale low Earth orbit (LEO) constellations carrying thousands of satellites brings formidable challenges. Strict resource limitations and visibility constraints trigger combinatorial explosion of feasible scheduling solutions. This paper proposes a three-phase progressive multi-beam scheduler (3PMS), which disassembles the complex integrated scheduling problem into hierarchically tractable subproblems. Phase I adopts a priority-aware first-come-first-served (FCFS) strategy combined with a dual-heap preemption mechanism to guarantee the execution of emergency tasks. Phase II implements load-balanced beam allocation based on a load-balance scoring function. Phase III introduces optimal execution window selection within visible arcs. Experiments are performed on two LEO constellation scenarios: the first is a single-shell orbital configuration with 1500 satellites, and the second is a three-shell architecture comprising 6080 satellites. Under extremely limited beam resources (1 beam), the worst-case single-beam capacity is 708 tasks per day, assuming every task consumes the maximum duration of 120 s, corresponding to 47.2% coverage for 1500 satellites and 11.6% for 6080 satellites. As the number of beams increases to five, all algorithms achieve 100% coverage for the 1500-satellite constellation, while the 6080-satellite constellation requires twenty beams for near-complete coverage. 3PMS demonstrates significant advantages in load balancing (Gini coefficient reduced from 0.0993 to 0.0003) and link quality (C/N improved by 5.5 dB). This paper verifies the feasibility of multi-beam scheduling algorithms for TT&C missions of large-scale satellite mega-constellations.