## 3 Assessment of Precise MGEX Orbit and Clock Products
### SLR Validation
#### 3.3.2 Bds  
Table 10 summarizes the mean bias as well as STD values of SLR residuals for different BDS orbit solutions. SLR residuals with absolute values larger than 1.0, 1.0 and 0.5 m were removed as outliers for the BDS GEOs, IGSO/MEO during the ON period and IGSO/MEO during the YS period, respectively. Note that most BDS-2 IGSO/MEO satellites use two attitude modes (YS and ON). Thus, the SLR validation results during the YS and ON periods are discussed separately for most BDS-2 IGSO/MEO satellites except C13, since C13 is reported not to enter ON mode [13; 42]. In the case of the YS \begin{table}
\begin{tabular}{c c c c c c c} \hline \hline  & **COD** & **ESM** & **GFZ** & **SHA** & **TUM** & **WUM** \\ \hline \multirow{2}{*}{C01} & \multirow{2}{*}{/} & \multirow{2}{*}{-} & \multirow{2}{*}{-} & \(-28.1\pm 22.2\)3  & \multirow{2}{*}{\(-33.8\pm 21.6\)} & \multirow{2}{*}{-} & \multirow{2}{*}{\(7.1\pm 9.8\)} \\  & & & & \(-12.6\pm 17.6\)4  & & & & \\ \hline \multirow{2}{*}{C08} & \multirow{2}{*}{YS  } & \(-1.0\pm 5.2\) & \(8.5\pm 9.3\) & \(0.5\pm 5.1\) & \(-2.1\pm 5.5\) & \(0.9\pm 9.7\) & \(-1.1\pm 6.2\) \\  & & \(-44.9\pm 37.0\)1  & \(1.7\pm 11.1\) & \(-2.5\pm 13.7\) & \(-0.8\pm 24.3\) & \(-18.4\pm 20.5\) & \(-3.1\pm 12.4\) \\  & & \(-6.2\pm 5.0\)2  & & & & \\ \hline \multirow{2}{*}{C10} & \multirow{2}{*}{YS  } & \(2.6\pm 5.2\) & \(9.4\pm 7.7\) & \(2.3\pm 4.9\) & \(-0.4\pm 5.6\) & \(3.8\pm 9.8\) & \(1.1\pm 5.5\) \\  & & \(-13.9\pm 24.7\)1  & \(4.9\pm 6.9\) & \(0.6\pm 9.3\) & \(0.2\pm 18.9\) & \(5.1\pm 15.4\) & \(1.8\pm 14.3\) \\  & & \(-6.7\pm 8.3\)2  & & & & \\ \hline \multirow{2}{*}{C13} & \multirow{2}{*}{/} & \multirow{2}{*}{\(1.9\pm 6.5\)} & \(9.1\pm 10.4\) & \(1.4\pm 6.0\) & \(-0.6\pm 6.3\) & \(1.1\pm 10.8\) & \(0.8\pm 5.6\) \\  & & \(\begin{array}{c}\text{YS}\\ -17.8\pm 34.3\)1 \\ -3.6\pm 14.0\end{array}\)1  & \(1.4\pm 10.2\) & \(-2.4\pm 10.8\) & \(0.9\pm 16.8\) & \(-8.7\pm 23.8\) & \(-1\pm 10.6\) \\ \hline \multirow{2}{*}{C20} & \multirow{2}{*}{/} & \multirow{2}{*}{-} & \(5.5\pm 5.6\) & - & - & - & \(4.6\pm 4.8\) \\ \hline \multirow{2}{*}{C21} & \multirow{2}{*}{/} & \multirow{2}{*}{-} & \(6.9\pm 5.7\) & - & - & - & \(6.4\pm 4.7\) \\ \hline \multirow{2}{*}{C29} & \multirow{2}{*}{/} & \multirow{2}{*}{-} & \(-4.6\pm 4.1\) & - & - & - & \(-2.1\pm 5.1\) \\ \hline \multirow{2}{*}{C30} & \multirow{2}{*}{/} & \multirow{2}{*}{-} & \(-5.5\pm 4.3\) & - & - & - & \(-2.6\pm 5.1\) \\ \hline \hline \end{tabular}  
* Statistics before DOY198 2018. 2 Statistics after DOY198 2018. 3 Statistics before DOY330 2018. 4 Statistics after DOY330 2018. 5 YS stands for yaw-steering period. 6 ON stands for orbit normal period.  
\end{table} 
Table 9: Mean bias and STD of Galileo satellite laser ranging (SLR) residuals (units: cm). period, COD, GFZ, SHA and WUM presented similar STD values of 5-6 cm for BDS-2 IGSO satellites (C08, C10 and C13) and 3-4 cm for the MEO satellite C11. TUM showed the largest STD values of about 10 cm for IGSOs and 7 cm for the MEO. While ESM showed a similar STD value of 4.3 cm for the MEO satellite as it did most other products, larger STD values of 8-10 cm were observed for IGSO satellites. ESM showed large mean biases of 8-9 cm for IGSOs and 4 cm for the MEO. In addition, the SLR residuals of ESM showed a clear dependency on the satellite-sun elongation angle for BDS-2 IGSO/MEO satellites (Figure 8) that was much more obvious than it was for any other product. In the case of the ON period, orbit accuracy was degraded significantly compared to that during the YS period for most products except the IGSOs of ESM. Although a tightly constrained acceleration bias in along-track direction was added for the BDS-2 MEO and IGSO satellites in WUM solution to compensate the deficiencies of the five-parameter ECOM in ON mode [5], the STD values in ON mode were still a factor of two to three worse compared to YS mode.