Fig. 1. Maximum and minimum background noise photon numbers at different times

Fig. 2. Schematic diagram of SNSPD response to photons

Fig. 3. Flow chart of Monte Carlo simulation

Fig. 4. Simulation results of the signal photon response under different noise conditions and noise-free photon response in previous recovery period

Fig. 5. Signal extraction threshold under different noise conditions

Fig. 6. Signal photon response number of geosynchronous orbit satellite QZS-2 under different orbital altitudes and noise intensity conditions

Fig. 7. Minimum cumulative duration required for geosynchronous orbit satellite QZS-2 under different orbital altitudes and noise intensity conditions

Fig. 8. Number of cycles required for relative error to be less than 10%

Fig. 9. Schematic diagram of signal transmission at Tianqin station

Fig. 10. QZS-2 satellite daytime test results @2024-11-30T16: 41. (a) Signal matching residual image; (b) signal strength within single-step cumulative duration

Fig. 11. Sun's altitude angle and angle between sun and target during SLR

Fig. 12. Signal strength results of target acquisition under different noise conditions and different single-step cumulative durations