# A Method to Determine BeiDou GEO/IGSO Orbital Maneuver Time Periods
## 3 Experimental Validation
### Orbital Maneuver Period Detection  
#### 3.2.1 Orbital Maneuver Period Detection for GEO Satellites  
The period of orbit maneuvering was determined for C01 on 9 January 2017. The performance of the start time factor series for XMIS is shown in Figure 4.  
In Figure 4, the start time factor series shows a sustained decreasing trend over about 5 h with values greater than 0 until 5:05:30. The start time of orbit maneuvering of C01 determined by the start time factor on 9 January 2017 is 5:05:30. The performance of the end time factor series for XMIS is shown in Figure 5. \begin{table}
\begin{tabular}{c c c c c c c c c c c c c c} \hline
**PRN** & **C01** & **C02** & **C03** & **C04** & **C05** & **C06** & **C07** & **C08** & **C09** & **C10** & **C11** & **C12** & **C13** & **C14** \\ \hline \(T_{Max}\) & 10.7 & 2.9 & 5.2 & 4.8 & 5.2 & 4.8 & 7.8 & 6.4 & 3.6 & 2.9 & 8.8 & 5.9 & 19.2 & 3.6 \\ \hline \end{tabular}
\end{table} 
Table 1: Thresholds of orbital maneuver detection for XMIS in 2017 (unit: meter). Figure 4: Start time factor of XMIS station for C01 on 9 January 2017: (**b**) detailed information from graph in (**a**). Figure 5: End time factor of XMIS station for C01 on 9 January 2017: (**b**) detailed information from graph in (**a**). In Figure 5, the end time factor series shows a sustained growth trend with values greater than 0 until the start at 5:33:00. The end time of the orbital maneuver of C01 detected by the end time factor on 9 January 2017 is 5:33:00. Thus, the period of orbit maneuvering for C01 can be determined by the start time and end time factors. In order to validate the results, the health status information of the satellite from broadcast ephemeris and to decide whether the satellite was included in the final precise orbit products of iGMAS and the German Research Centre for Geosciences (GFZ), GFZ was used as a reference. The parameters of C01 from broadcast ephemeris and the header information of precise orbit products on 9 January 2017 are shown in Figures 6 and 7, respectively. In Figure 6, the status of C01 is marked as unhealthy from 04:00 to 11:00. The period of orbital maneuver determined for C01 is 5:05:30 to 5:33:00 (between 4:00:00 and 11:00:00). As is known, after orbit maneuvering, the orbital parameters of the satellite are different from the previous parameters. Once the orbit is maneuvered, the precise orbit of C01 cannot be determined because orbit maneuvering  
Figure 6: Broadcast ephemeris of C01. The red box highlights the unhealthy status marked as 1. The blue box highlights the healthy status marked as 0. Note that the data are not displayed between 4:00:00 and 11:00:00 to limit the height of the figure and the healthy statuses are all marked as 1 in this period. Figure 7: Information of precise orbit products from International Global Navigation Satellite System (GNSS) Monitoring and Assessment System (iGMAS) and German Research Centre for Geosciences (GFZ) on 9 January 2017. The red box highlights the satellite removed from the header of precise orbit products. The blue box marks the abbreviation of the organization providing the products. leads to failure of the kinetic empirical parameters. The precise orbit products did not include the C01 in Figure 7, which is secondary proof of the orbit maneuvering for C01. Although the period of unhealthy marks of C01 from broadcast ephemeris include the determined period of orbital maneuver and the precise products of iGMAS and GFZ removing the C01 satellite, the orbit maneuvering period determined by this method needs to be verified that it is near the real period of orbit maneuvering. Therefore, the bias between pseudo-range SPP coordinates of DARW station and the reference coordinates from IGS SINEX are used to verify the correction of the determined period. The bias of DARW on 9 January 2017 is shown in Figure 8.  
Figure 8 shows the detected start time of the orbit maneuvering. The red marks represent the series before the start time, and the blue marks represent the series after the start time.