## 4 Experimental Results and Analysis
### Assessment of Multi-Rx and Multi-Tx LEO-LEO Occultation Constellation Performance
#### 4.3.2 Performance of Two-Orbit Constellations  
Figure 11a-c, Figure 11d-f, and Figure 11g-i illustrate the 1-day, 3-day, and 9-day global coverage of occultation events for the Rxi98-Txi98 2 Rx/2 Tx, 6 Rx/6 Tx, and 12 Rx/12 Tx constellations, respectively. As shown in Figure 11a-c, the 1-day, 3-day, and 9-day global coverage fractions of 2 Rx/2 Tx occultation events are about 8%, 25%, and 63%, respectively. As shown in Figure 11d-f, the 1-day, 3-day, and 9-day global coverage fractions of 6 Rx/6 Tx occultation events are about 50%, 76%, and 100%, respectively, which is much higher \begin{table}
\begin{tabular}{c c c c c} \hline \hline \multicolumn{2}{c}{**Experiment Groups**} & \multicolumn{4}{c}{**Orbit Elements (Rx/Tx)**} \\ \cline{2-5}  & **I (\({}^{\circ}\))** & **RAAN (\({}^{\circ}\))** & **M0 (\({}^{\circ}\))** \\ \hline \multirow{3}{*}{**Rxi98-Txi98**} & 2 Rx/2 Tx & 98/98 & 180/0 & 30, 120/150, 240 \\  & 6 Rx/6 Tx & 98/98 & 180/0 & 30:60:360/30:60:360 \\  & 12 Rx/12 Tx & 98/98 & 180/0 & 30:30:360/30:30:360 \\ \hline \multirow{3}{*}{**Rxi140-Txi40**} & 2 Rx/2 Tx & 140/40 & 180/0 & 30, 120/150, 240 \\  & 6 Rx/6 Tx & 140/40 & 180/0 & 30:60:360/30:60:360 \\  & 12 Rx/12 Tx & 140/40 & 180/0 & 30:30:360/30:360 \\ \hline \multirow{3}{*}{**Multiple orbits of**} & 2 Rx/2 Txorbit & 98/98 & 0, 90/180, 270 & 30:60:360/30:60:360 \\  & 4 Rx/4 Txorbit & 98/98 & 30:30:120/210:30:300 & 30:60:360/30:60:360 \\ \cline{1-1}  & 6 Rx/6 Txorbit & 98/98 & 0:30:150/180:30:330 & 30:60:360/30:60:360 \\ \hline \hline \end{tabular}
\end{table} 
Table 3: The main orbital parameters of the transmitting and receiving satellites for multi-Rx and multi-Tx constellations. The chosen set of values for some elements is denoted in the format of StartValueStep:EndValue; simulations were performed using an ensemble of configurations stepping through all value settings for these elements. than those of the 2 Rx/2 Tx constellation; specifically, the 9-day global coverage fraction reaches 100%. As shown in Figure 11g-i, the 1-day and 3-day global coverage fractions of 12 Rx/12 Tx occultation events reach 67% and 86%, respectively. The 9-day global coverage fraction of 12 Rx/12 Tx occultation events reaches 100% with uniform global coverage, and the number of single-grid occultation event revisited times in some areas is more than 40, which can basically meet the requirements of global climate monitoring [18]. The global coverage fractions and the number trend of the occultation events for the Rxi98-Txi98 2 Rx/2 Tx, 6 Rx/6 Tx, and 12 Rx/12 Tx constellations are shown in Figure 12. One can see that with the increase in the number of Rx and Tx satellites, the slope of the number and GCF curves increases significantly. Specifically, the 6 Rx/6 Tx constellation achieves a global coverage fraction of 100% in 8 days, and the 10-day occultation number reaches more than 61,000. The 12 Rx/12 Tx constellation achieves a global coverage fraction of 100% in just 7 days, and the 10-day occultation number reaches more than 86,000. Figure 13a-c, Figure 13d-f, and Figure 13g-i illustrate the 1-day, 3-day, and 9-day global coverage of occultation events for the Rxi140-Txi40 2 Rx/2 Tx, 6 Rx/6 Tx, and 12 Rx/12 Tx constellations, respectively. As shown in Figure 13a-c, the 1-day, 3-day, and 9-day global coverage fractions of 2 Rx/2 Tx occultation events are about 11%, 32%, and 49%, respectively. As shown in Figure 13d-f, the 1-day, 3-day, and 9-day global coverage fractions of 6 Rx/6 Tx occultation events are about 50%, 70%, and 75%, respectively, which is much higher than those of the 2 Rx/2 Tx constellation, and the number of times a single grid cell is revisited has increased significantly. As shown in Figure 13g-i, the 1-day, 3-day, and 9-day global coverage fractions of 12 Rx/12 Tx occultation events reach 69%, 71%, and 77%, respectively.