Objectives Laser inter-satellite link (LISL) of the navigation constellation has been assigned with constraints of the 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 includes two states, transition state and steady state. The transition state completes the link switching and reconstruction, and maintaines 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 is established. A multi-objective optimization algorithm for link topology based on non-dominated sorting genetic algorithm-II (NSGA-II) is 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 is realized while ensuring the steady-state ranging and communication performance.

Results The assignment and simulation of a global navigation constellation LISL were carried out. The optimal solution set generated by NSGA-II could dominate the optimal solution generated by the multi-objective simulated annealing algorithm. The ranging position dilution of precision of steady-state LISL topologies corresponding to the comprehensive optimal solution of all link periods ranged from 1.9 to 3.2, and the communication delay ranged from 0.14 to 0.34 s. The transition state communication delay ranged from 0.14 to 0.43 s.

Conclusions The proposed laser link assignment method is able to realize efficient inter-satellite ranging and communication in steady link states, and ensures the whole constellation network connectivity and satellite-to-earth communication in link transition states.