## 3 Results
### Verification of the a Priori Model  
Based on the four sets of optical parameters obtained in Figure 4, an a priori SRP model of the rectangular body of the BDS-3 MEO satellite was established. The ECOM model was used to absorb the SRP acceleration introduced by the solar panel and the residual accelerations. To validate the performance of the model, only L-band observations were used in the POD. The test periods and datasets are consistent with the modeling. The accuracy of the a priori model was verified in terms of SLR residual distribution and clock accuracy. Figure 8 presents a comparison of the SLR residuals derived from the a priori models constructed based on G1 and J1 strategies. A systematic linear trend is depicted using the ECOM model without the a priori satellite body model. The slopes are about \(-0.097\) cm/deg and \(0.067\) cm/deg for C21 (CAST) and C30 (SECM) satellites, respectively. The a priori model employing the adjusted optical parameters can significantly weaken the systematic trend induced by the ECOM model. Comparison of the a priori models reveals that the a priori model established by both the ISL and L-band observations can almost eliminate the systematic trends in the SLR residuals. The slopes of CAST and SECM are reduced to \(-0.004\) cm/deg and \(-0.009\) cm/deg, which are better than those obtained by using L-band observations. The distribution of SLR residuals is depicted in Figure 9. After adopting the a priori model, the discrete degree was significantly reduced and the a priori model based on J1 was slightly better than the one based on G1. For CAST and SECM satellites, the STD values of the ECOM+J1 strategy decreased from 4.2 cm and 4.6 cm to 3.3 cm and 3.5 cm, respectively. We can also see that the mean value using the a priori model constructed based on J1 is smaller than that of G1. The incorporation of ISLs led to greater improvement in the a priori model for the SECM satellite. This distribution indicates that the a priori model established by J1 is more accurate. For satellites not observable by SLR stations, Table 5 compares the averaged DBD of their orbits and OADEVs of their clock offsets. The DBD of the CAST satellites did not decrease by employing the ECOM model with the a priori satellite body model, which suggests that the model needs to improve the internal consistency. Furthermore, a slight improvement in DBD was observed for the a priori model established on SAR. Concerning the systematic clock offset trend, Figure 10 demonstrates a sequential decrease in the OADEV trend of C20 and C30 satellites for the ECOM, ECOM+G1, and cJ1 models. For the C33 satellites that consider its SAR panels, the \(\beta\) dependence of OADEV estimated by ECOM+J1/J2 shows less variation compared to ECOM+G/G2 in Figure 11, notably within the range of [\(-40^{\circ}\), \(40^{\circ}\)]. Regarding the SECM-B satellite, no specific trends are observed. The average OADEV with the a priori model introducing the ISL is slightly better than that established by the ground station, and the results considering the SAR antenna outperform those without its consideration. \begin{table}
\begin{tabular}{l c c c c c c c} \hline \hline \multicolumn{1}{c}{\multirow{2}{*}{**\# of Normal Point**}} & \multicolumn{3}{c}{**G1**} & \multicolumn{3}{c}{**J1**} \\ \cline{2-7}  & **Bias** & **STD** & **RMS** & **Bias** & **STD** & **RMS** \\ \hline C20 & 2646 & 1.9 & 2.8 & 3.4 & 2.1 & 2.1 & 2.9 \\ C21 & 2746 & 3.0 & 2.8 & 4.1 & 3.0 & 2.3 & 3.8 \\ C29 & 2032 & 4.9 & 4.2 & 6.4 & 0.5 & 2.4 & 2.5 \\ C30 & 1848 & 4.9 & 3.4 & 6.0 & 0.7 & 2.6 & 2.7 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: SLR residuals of G1 and J1 strategies of SRP modeling (unit: cm). Figure 8: SLR residual estimated by ECOM (left column), ECOM+G1 (middle column), and ECOM+J1 (right column) dependent on \(\varepsilon\) angle. The red line represents the linear trend line, with the slope value (red font) denoted in cm/deg. Figure 9: SLR residual distribution based on ECOM (blue), ECOM+G1 (green), and ECOM+J1 (red).