# A Method to Determine BeiDou GEO/IGSO Orbital Maneuver Time Periods
## 4 Discussion and Conclusions  
This study proposes an approach to determine periods of orbit maneuvering using publicly broadcast data. The orbit after maneuvering can be calculated by the measured orbit of the day, which supplements the position of satellites for about 7-8 h in the broadcast ephemeris. The observations of MGEX stations, the measured orbits published by CHD, and the coordinates of stations referenced from IGS SINEX were selected to validate the detection method. The results show that periods of orbit maneuvering can be detected accurately for BeiDou GEO and IGSO satellites. In addition, the orbital maneuvering periods of other GNSS MEO satellites can also be determined by this method. Figure 14: Time series of orbital semimajor axis of G11 in 2018: (**b**) detailed information of the red box (days 059–061) in (**a**). Figure 13: Detection results of KIRI station for G11 on 1 March 2018. (**a**) Start time factor of KIRI station for G11 on 1 March 2018; (**b**) end time factor of KIRI station for G11 on 1 March 2018. Note: the data of station KIRI with a 30 s sampling period from Multi-GNSS Experiment (MGEX) are selected to be analyzed. Comparing the method in this study with our previous research methods, referring to [17; 18], the first method in previous research methods to detect the start time of orbit maneuvering is based on the mean square unit weight error of SPP technology, which is according to the internal accuracy; the second method in previous research methods detects the start time by the difference of pseudo-range observations and the distance calculated by broadcast ephemeris and station coordinates. The two methods can detect only one orbit switching time because the orbit after maneuvering is inaccurate from broadcast ephemeris. In addition, the variation of pseudo-range observations is small due to the orbital maneuvers, which could not be considered in previous research. It causes the detected start time of orbit maneuvering to have some latency, but the average time of orbital maneuver difference between the detected start time and the marked started time of the broadcast ephemeris is 91 min in 2017. It means that the proposed method can extend the usable observations for a few hours when the satellite is maneuvered for users. Thus, the method proposed in this paper can detect the start time and end time of orbit maneuvering more accurately, and the period of orbit maneuvering can be determined. The result of period detection for orbit maneuvering provides important reference information for precision orbit and clock offset determination when carrying out satellite maneuvers. In our next research, the detection results of orbit maneuvering of this study will be used to determine the orbit and clock offset in order to improve the integrity of precision orbit and clock products. [PERSON] and [PERSON] provided the initial idea for this study; [PERSON], [PERSON], [PERSON], [PERSON] and [PERSON] conceived and designed the experiments; [PERSON], [PERSON] and [PERSON] analyzed the experimental results; [PERSON], [PERSON] and [PERSON] wrote the paper. This work was supported by the National Key R&D Program of China (2018 YFC1505102), the Programs of the National Natural Science Foundation of China (41774025, 41731066), the Special Fund for Technological Innovation Guidance of Shaanxi Province (2018 XNCGG05), the Special Fund for Basic Scientific Research of Central Colleges (grant No. CHD300102269305, CHD300102268305, Chang'an University), and the Grand Projects of the Beidou-2 System (GFZX0301040803). The authors would like to thank IGS and iGMAS for the data support. Some of this material is based on data services provided by MGEX ([[http://www.igs.org/mgex](http://www.igs.org/mgex)]([http://www.igs.org/mgex](http://www.igs.org/mgex))).