Safe backup strategy for on-orbit satellites in large-scale LEO constellation

To avoid the risks of satellite collisions in Low Earth Orbit (LEO) large-scale constellation, this study conducts an internal collision risk assessment for given constellation configuration. First, the expressions for the risky and safe phase distance within the orbital plane of an arbitrary constellation are derived using spherical trigonometry; Second, the constellation configuration parameters are then optimized to maximize the safe phase distance. Finally, a design method of on-orbit backup satellite orbits is proposed based on the safe phase distance optimization. The experimental results show the backup strategy with safe phase distance optimization achieves controlled and safe on-orbit backup with minimal impact on the original constellation configuration, in which safe phase distance reduced to 1/2 of the original value on one side in parts of on-orbit satellites.