## 5 Simulation and Analysis of Positioning Strategy of Constellation Station  
### Simulation Scheme and Result Analysis of Absolute Station-Holding Strategy  
1. Setting of simulation conditions. The large-scale Walker constellation selected in the simulation had a configuration of Walker \(60/3/1\). (The concept of the Walker-\(\delta\) constellation was first proposed by [PERSON] of the Royal Aircraft Establishment in the UK in 1971. The Walker-\(\delta\) constellation can be represented by the configuration code N/P/F. Among them, N represents the total number of satellites in the constellation, P represents the total number of orbital planes in the constellation, and F represents the phase factor of satellites in adjacent orbital planes of the constellation [26]). It also had an orbital altitude of 550 km and an orbital inclination of 53\({}^{\circ}\). The satellite phase angle drift ring was simulated within a range of \(\pm 0.1^{\circ}\). The perturbation model was the Earth non-spherical \(J_{2}\) perturbation model. The Jacchia 71 atmospheric density model (set) was used, and the orbit prediction model was the HPOP model. The satellite surface-to-mass ratio was 0.01, the phase retention mission period was 100 days, and \(C_{d}=2.2\). Table 2 presents the details for satellite number 1 in the constellation. The phase-holding task of satellite 1 was simulated. The statistical results of the phase-holding period and semi-major axis change of satellite 1 are shown in Figure 6, and those of the phase-maintenance period and phase difference change of satellite 1 are shown in Figure 7. As can be seen from the simulation results, in the nearly 100-day phase-holding period of satellite 1, the phase-holding control period was about 13.1 days, the maximum adjustment of the semi-major axis was about 70.7 m, and the phase angle deviation was basically kept within \(\pm 0.1^{\circ}\). These results verified the effectiveness of the absolute station phase-holding ring method and achieved the expected phase-holding task. Figure 4: Decay of satellite 1 semi\(-\)major axis in low\(-\)solar\(-\)activity years. Figure 5: Decay of average value of the semi\(-\)major axis of satellite 1 in high\(-\)solar\(-\)activity years. \begin{table}
\begin{tabular}{c c c c c c} \hline \hline  & \multirow{2}{*}{\begin{tabular}{c} **Initial** \\ **Satellite** \\ **Number** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Maximum** \\ **Initial** \\ **Semi-** \\ **Major** \\ **Axis/km** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Adjustment** \\ **Amount of Average** \\ **Value of the** \\ **Semi-Major Axis in** \\ **Semi-Major Axis in** \\ **Years of Low** \\ **Solar Activity/m** \\ \end{tabular} } & \multirow{2}{*}{\begin{tabular}{c} **Maximum** \\ **Adjustment of** \\ **Semi-Major Axis of High-** \\ **Solar-Activity** \\ **Year/m** \\ \end{tabular} } & \multirow{2}{*}{\
\begin{tabular}{c} **Maximum Interval of** \\ **Adjustment Time for** \\ **Average Value of the** \\ **Semi-Major Axis of High-** \\ **Low-Solar-Activity** \\ **Year/d** \\ \end{tabular} } & \multirow{2}{*}{
\begin{tabular}{c} **Maximum Interval for** \\ **Adjustment of** \\ **Average Value of the** \\ **Semi-Major Axis of High-** \\ **High-Solar-Activity** \\ **Year/d** \\ \end{tabular} } \\
1 & 6925.6 & 29.4 & 70.7 & 13.1 & 5.5 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: Satellite control parameter settings. The statistical results of the time interval of the orbit maneuvering and the change of the semi-major axis during phase holding are shown in Table 4. The average holding period of satellite 1 in a single phase-holding mission was 13.29 days, and the change in the semi-major axis in a single orbital maneuver was 59.79 m. In the whole phase-holding task, the orbital maneuver time totaled 92.71 days, and the total orbital maneuver semi-major axis change was 418.56 m.  
Figure 8 more directly reflects the time interval of the orbital maneuvering and the change of the semi-major axis of satellite 1 in the phase-holding task. The deviation of the