# Multi-Satellite Observation-Relay Transmission-Downloading Coupling Scheduling Method
## 4 Simulation Results
### Scenario 1 Insufficient Electric Energy Scenario
Figure 5 presents the iterative results of different methods in a single condition of scenario 1. The comparison between the orange dashed line and the green dashed line in the figure illustrates the impact of the improvement in tabu search. The improved tabu search method escaped from the local optimum and searched toward a more optimal solution after 15 iterations. In contrast, the traditional tabu search method did not escape from the local optimum until 143 iterations. The final result of the improved tabu search method was also better than the traditional tabu search method. It can be seen from the figure that the solutions of SASRD and GASRD are continuously improved, which reflects that SASRD and GASRD have global search ability and potential. However, due to the \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & \multicolumn{3}{c}{**Optimal Solution**} & \multicolumn{3}{c}{**Optimal Solution**} \\  & \multicolumn{3}{c}{**Objective Function Value**} & \multicolumn{3}{c}{**Iteration Time (s)**} \\ \cline{2-7}
**Method** & **Max** & **Min** & **Average** & **Max** & **Min** & **Average** \\ \hline CTSND & 73.06 & 67.70 & 70.56 & 53,449.45 & 43,823.98 & 47,950.01 \\ CTSTD & 61.52 & 52.24 & 56.68 & 62,552.34 & 29,555.25 & 48,103.63 \\ CTSRD 1  & 73.06 & 67.70 & 70.20 & 60,007.70 & 36,706.24 & 47,109.22 \\ SASRD & 72.87 & 64.82 & 68.59 & 68,923.34 & 51,544.14 & 61,194.55 \\ GASRD & 69.81 & 63.58 & 67.13 & 77,119.22 & 56,474.78 & 64,570.52 \\ ITSRD 2  & 74.80 & 69.45 & 72.88 & 40,172.14 & 22,252.50 & 32,140.57 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Statistical results of different methods in scenario 1. Figure 4: Targets and ground stations distribution in scenario 1.  
length of time of the single-step solutions, SASRD and GASRD need more time to achieve optimal solutions. Figures 6-8 show the observation and data transmission event diagram of different methods: the red strips are the observation period, the green strips are the inter-satellite output data transmission period, the blue strips are the inter-satellite input data transmission period, the yellow strips are the satellite-ground data transmission period, the black strips are the inter-satellite data transmission time window, and the white strips are the ground data transmission time window. The timing relationship between the observation periods, the inter-satellite data transmission periods, and the satellite-ground data transmission periods in the figures shows that the multi-satellite observation-relay transmission-download coupling scheduling method can realize the whole process of scheduling multi-satellite observation, relay transmission, and downloading. It can be seen from the number of blue and green strips in Figures 6 and 7 that CISRD performed less inter-satellite data transmission than CTSTD, so more electric energy could be used for target observation and data transmission of CTSRD and more missions could be completed, thus the objective function value was better. For the insufficient electric energy on satellites 1 and 2, ITSRD performed fewer observation missions than CTSRD, reducing the consumption of attitude maneuver electric energy to complete more inter-satellite data transmission missions and satellite-download data transmission missions, thus the objective function value was better. This shows that the improved tabu search algorithm helps the satellite cluster observe more targets by adjusting the state of the satellite electricity subsystem and indicates the improvement of using the subsystem coupling relationship to help the search method escape from the local optimum.