## 4 Experiments and Analysis
### Impact on the Orbital Accuracy  
In this section, we analyze the impact of different experimental strategies on the orbit accuracy, including using different prior orbits and adopting different types of observations, as mentioned in Table 4. Specifically, the consistency among various days, the averaged RMS in each direction for every satellite, and the orbital accuracy for different types of satellites were analyzed in sequence. It should be noted that the precise ephemeris provided by the Wuhan University Analysis Center was chosen as the reference to assess the orbital accuracy for all experiments. Firstly, from the perspective of the consistency among various days, we analyzed the performance of the determined orbit in all the experiments. Using a three-dimensional (3D) example, Figure 7 illustrates the orbital RMS among the various days for each satellite in each experiment. In each subgraph, the horizontal axis represents the satellite, and the vertical axis denotes the statistical value of the RMS in the 3D direction. Different colored dots represent different days. Specifically, the top panel shows the results of using only ISL observations, while the bottom panel shows the results of introducing the SLR observation for orbit determination. Figure 7: Orbital 3D RMS of every satellite on multiple days. The left column is based on the broadcast ephemeris as the a priori orbit, while the right details the precise ephemeris as the a priori orbit. It can be observed from Figure 7 that, overall, there is good consistency among multiple days. In addition, on the one hand, by observing the left and the right columns of the graph, it can be seen that, compared to the results using broadcast ephemeris as the a priori orbit, the consistency among various days is more obvious when using the precise ephemeris as the a priori orbit. The 3D RMS of the orbit is approximately 100 cm and below 50 cm, respectively, signifying an enhancement in precision by nearly three times. This phenomenon may be related to the orbit accuracy and reference frames of the broadcast ephemeris and the precise ephemeris [38]. On the other hand, by comparing the upper and lower subgraphs, it can be seen that the introduction of SLR observation to ISL for combined orbit determination improved the overall orbit accuracy. In addition, it is interesting that in Experiments 2 and 4, shown in Figure 7, that, except for the IGSO satellite, the orbital accuracies of the satellite C25 and C26 are slightly lower than those of other satellites. We preliminarily think that this phenomenon is related to the on-orbit characteristics of the antenna phase center deviation of the ISL, which was described in our previous study [29]. Then, to further explore the impact of the a priori orbit and the involved observations on the orbital accuracy in various directions, we counted the RMS value of each satellite in three directions by averaging the values from multiple days. Figure 8 illustrates the statistical RMS for each satellite in along, cross, radial, and 3D directions, respectively. Figure 8: Average orbital accuracy for all satellites in four experiments. Similarly, the horizontal axis represents the satellite, while the vertical axis denotes the RMS of the orbit in each direction. The subfigures from top to bottom depict the RMS of the orbit in the along, cross, radial, and 3D directions, respectively. Different colored bars represent different experiments. The blue bars indicates Experiment 1, which only utilizes ISL observations with broadcast ephemeris as the a priori orbit. The red ones represents Experiment 2, which also only utilizes ISL observations but with precise ephemeris as the a priori orbit. The yellow and purple bars express the results of Experiment 3 and Experiment 4, respectively. Both of these two experiments introduced the SLR observation for ISL/SLR combined orbit determination, but with different a priori orbits.