Laser Link Assignment of Navigation Satellite Constellations Considering Inter-satellite Ranging and Communication

Objectives: Laser Inter-Satellite Links (LISLs) of the navigation constellation was assigned with constraints of inter-satellite visibility, the number of laser terminals and the link system to realize efficient inter-satellite ranging and communication with ground stations. Methods: According to the laser link system, each link period included two states, transition state and steady state. The transition state completed the link switching and reconstruction, and maintained a static link topology when entering the steady state. Based on the static processing, a multi-objective assignment model of steady-state LISL of navigation constellations was established. A multi-objective optimization algorithm for link topology based on Non-dominated Sorting Genetic algorithm-II (NSGA-II) was proposed. By introducing the edge connectivity constraint of the transition topology into the steady-state optimization model, the whole network connectivity in the transition state was realized while ensuring the steady-state ranging and communication performance. Finally, the assignment and simulation of a global navigation constellation LISL were carried out. Results: The optimal solution set generated by NSGA-II could dominate the optimal solution generated by the Multi-Objective Simulated Annealing Algorithm (MOSA). The ranging PDOP of steady-state LISL topologies corresponding to the comprehensive optimal solution of all link periods was 1.9~3.2, and the communication delay was 0.14 ~0.34s. The transition state communication delay ranged from 0.14s to 0.43s. Conclusions: The results demonstrated that the proposed laser link assignment method could realize efficient inter-satellite ranging and communication in steady link states, and ensure the whole constellation network connectivity and satellite-to-earth communication in link transition states.