## 5 Performance Assessment of BDS-3 Satellite Clocks
### Results  
The differenced data between the clock data of one GNSS satellite and the receiver clock of the ground station KOUR attached to the high-precision AHM were derived. Then, the data editing procedures were completed, as described in Section 2. Figure 9 presents the clean frequency data of each BDS-3 satellite, where we see there are almost no jumps or outliers. Then, the BDS-3 atomic clock performance was derived. Figure 10 is the averaged frequency accuracy and frequency drift rate during the whole assessment period. It can be seen that the frequency accuracy of BDS-3 PHM is slightly better than BDS-3 RAFS, while the frequency drift rate is significantly superior. The frequency drift rate of BDS-3 with PHM when excluding C34 and C35 is \(1.44\times 10^{-15}\), which is about two orders of magnitude better than that of BDS-3 RAFS satellites, showing the good performance of the PHM clock. Figure 11 gives the averaged frequency stability with the averaging time of 300 s, 10,000 s, and 86,400 s. The stability is basically comparable among BDS-3 satellites with the same clock type. The HDEV is basically comparable between BDS-3 RAFS and PHM satellites at the averaging time of 300 s, while the stability of 10,000 s and 86,400 s for BDS-3 PHM is better than BDS-3 RAFS, especially the 1 d stability \begin{table}
\begin{tabular}{c c c c c c} \hline \hline \multirow{2}{*}{**Station Diff.**} & \multirow{2}{*}{**Accuracy**} & \multirow{2}{*}{**Drift Rate**} & \multicolumn{3}{c}{**Stability**} \\ \cline{3-6}  & & & **300 s** & **10,000 s** & **1 Day** \\ \hline MGUE-KOUR & \(5.66\times 10^{-14}\) & \(4.70\times 10^{-16}\) & \(5.26\times 10^{-14}\) & \(8.93\times 10^{-15}\) & \(1.85\times 10^{-15}\) \\ \hline NOVM-KOUR & \(2.29\times 10^{-14}\) & \(2.48\times 10^{-16}\) & \(1.11\times 10^{-13}\) & \(1.41\times 10^{-14}\) & \(3.14\times 10^{-15}\) \\ \hline PTBB-KOUR & \(2.18\times 10^{-14}\) & \(2.56\times 10^{-16}\) & \(5.69\times 10^{-14}\) & \(1.09\times 10^{-14}\) & \(3.04\times 10^{-15}\) \\ \hline Averaged value & \(3.38\times 10^{-14}\) & \(3.25\times 10^{-16}\) & \(7.35\times 10^{-14}\) & \(1.13\times 10^{-14}\) & \(2.68\times 10^{-15}\) \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Statistics of ODTS noise. \begin{table}
\begin{tabular}{c c c c} \hline \hline
**GNSS** & **Satellite Type** & **PRN** & **Clock Type** \\ \hline \multirow{3}{*}{BDS-2} & GEO & C01 C02 C03 C04 C05 & \\  & IGSO & C06 C07 C08 C09 C10 C13 C16 & RAFS \\  & MEO & C11 C12 C14 & \\ \hline \multirow{3}{*}{BDS-3} & MEO & C20 C21 C22 C23 C24 C32 C33 C36 C37 & RAFS \\  & MEO & C25 C26 C27 C28 C29 C30 C34 C35 & PHM \\ \hline GPS & IIF & G01 C03 G06 C09 C10 C25 G26 G27 G30 G32 & RAFS \\  & IOV & E12 E19 & \\ \multirow{3}{*}{Galileo} & FOC & E01 E02 E03 E04 E05 E07 E08 E09 E13 E15 E21 & \\  & FOC & E24 E25 E26 E27 E30 E31 E33 E36 & \\ \hline \hline \end{tabular}
\end{table} 
Table 5: GNSS satellite PRN and clock type used in the analysis. Figure 9: Frequency offsets of the differenced values between BDS-3 satellite clocks and KOUR station clocks. Figure 12 summarizes the results of GNSS clock assessment in terms of the frequency accuracy, drift rate (daily), and stability at the averaging time 300 s, 10,000 s, and 86,400s, during the data processing period. The frequency accuracies of BDS-3 RAFS and PHM are 0.3-\(4\times 10^{-11}\) and 0.5-\(3\times 10^{-11}\), with the average values of \(2.29\times 10^{-11}\) and \(1.48\times 10^{-11}\), respectively, while for GPS satellites with RAFS, it is 0.2-\(1\times 10^{-11}\) and the average value is \(9.30\times 10^{-12}\). Correspondingly, the frequency accuracy of Galileo satellites with PHM is \(9.37\times 10^{-12}\) with a large variation range of \(3\times 10\)-\(14\)-\(4\times 10^{-11}\). The averaged frequency accuracies of BDS-2 GEO, IGSO, and MEO satellites with RAFS are \(9.09\times 10^{-11}\), \(2.05\times 10^{-11}\), and \(1.69\times 10^{-11}\), respectively, which is comparable to the results of [34].