# BDS Orbit Maneuver Detection Based on Epoch-Updated Orbits Estimated by SRIF
## 3 Data Processing and Validation
### Experimental Results and Verification
From 07:31:00, there was no significant change in the cross-track component of the orbit differences, but the along-track component exhibited a rapid increase. It was easy to detect that the C24 satellite had an orbit maneuver at 07:31:00 on the 325 th day of 2022. Second, as shown on the right-hand side of Figure 8, prior to 07:31:00, the orbit difference in the along-track direction was rapidly decreasing. From 07:32:30, it reached a stable state. However, the orbit difference in the cross-track direction fluctuated between 07:32:30 and 07:37:00, and only after that did it tend towards a stable state. Therefore, it can be concluded that the time for the C24 satellite to return to a stable state was 07:37:00 on the 325 th day of 2022, which can be regarded as the end time of the orbit maneuvering. In addition, we conducted an experimental verification of the real-time detection method for the end time of the maneuver proposed in this paper. The experimental results, shown in Figure 9, correspond to the time series of Equation (4). From the left-hand side in Figure 9, it can be clearly seen that before the orbit maneuvering start time, the values in along-track and cross-track directions were in a stable state, and randomly distributed around zero, there was a large jump due to gross errors. However, this jump did not affect the detection results of the start time of orbit maneuvering. The start time of orbit maneuvers can be detected in real time using the previous method, and it has been marked. During the orbit maneuvering, the values had a significant jump in both the along-track and cross-track directions, particularly along-track, due to the thrust exerted on the satellite. Once the satellite returned to stability, the values began to stabilize, enabling us to detect the end time of orbit maneuvering for the C59 satellite as 09:05:00. Similarly, based on the results in the middle and on the right-hand side, we can detect the end time of the orbit maneuvers for the C39 and C24 satellites as 09:08:00 and 07:37:00, respectively. Compared to the post-detection results of the above orbit maneuver end times, there was only a one-minute delay for the C39 satellite, which can be seen as negligible compared to the hours-long delay in the broadcast ephemeris. Figure 8: The orbit maneuver detection for C24 satellite on 325 th day of 2022. This is the same as Figure 6, but for a different satellite in a different day. As the official publication of orbit maneuver information for the BeiDou satellites is not publicly available, we estimated the velocity pulses of the satellites using batch least squares to verify the accuracy of the detection results in this study. To avoid the effect of the position and velocity in the radial direction, which have a strong correlation with the clock offset, on the estimated velocity pulses, we only estimated the velocity pulses pseudo-random parameters in the along and cross directions. The results for MEO/IGSO and GEO satellites are shown in Figures 10 and 11. The results clearly indicate that the values of the velocity pulses in the along-track and cross-track directions of the satellite remained stable at below 3 mm during the non-maneuver period. These values began to gradually increase at 07:29:30, reaching a maximum value of approximately 60 mm/s at 07:30:30, and returned to a stable state at 07:34:00. In this study, the detection period was from 07:30:30 to 07:37:00. Upon comparison, it was found that the start time differed by 1 min, and the end time differed by 3 min. The verification results for IGSO satellite are presented below. Figure 10: The velocity pulse estimated for C24 satellite on 325 th day of 2022. The estimation results of velocity pulses of the C24 satellite in along and cross directions are shown from left to right, with the combined value on the right part, represented by blue, orange, and cyan dots. The horizontal axis denotes the time axis on the 325 th day of 2022, and the shaded area represents the detection results of orbit maneuver period in this study.