# A Method to Determine BeiDou GEO/IGSO Orbital Maneuver Time Periods
###### Abstract  
Because there are different types of BeiDou constellations with participating geostationary orbit (GEO) and inclined geosynchronous orbit (IGSO) satellites, the maneuvering frequency of BeiDou satellites is higher than that of other navigation systems. The satellite orbital maneuvers lead to orbital parameter failure for several hours from broadcast ephemeris. Due to the missing initial orbit, the maneuvering thrust, and the period of orbital maneuvering, the orbit products of maneuvering satellites cannot be provided by the International Global Navigation Satellite System (GNSS) Service (IGS) and International GNSS Monitoring and Assessment System (iGMAS). In addition, the period of unhealthy status and the orbital parameters of maneuvering satellites in broadcast ephemeris are unreliable, making the detection of orbital maneuver periods more difficult. Here, we develop a method to detect orbital maneuver periods involving two key steps. The first step is orbit prediction of maneuvering satellites based on precise orbit products. The second step is time period detection of orbit maneuvering. The start time detection factor is calculated by backward prediction orbit and pseudo-range observations, and the end time detection factor is calculated by forward prediction orbit and pseudo-range observations. Data of stations from the Multi-GNSS Experiment (MGEX) and iGMAS were analyzed. The results show that the period of orbit maneuvering could be detected accurately for BeiDou GEO and IGSO satellites. In addition, the orbital maneuver period of other GNSS medium Earth orbit (MEO) satellites could also be determined by this method. The results of period detection for orbit maneuvering provide important reference information for precision orbit and clock offset determination during satellite maneuvers. GEO/IGSO; period detection; orbital maneuver; time periods; orbit prediction 2019  
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maneuvering is higher than MEO satellites [7; 8; 9; 10]. During orbit maneuvers, the dynamic models for determining the orbit are different during maneuvering and non-maneuvering periods. The kinetic model is unknown because of the secret maneuvering thrust during the orbit maneuvering period, but the orbit of the non-maneuvering period can be determined by the normal kinetic model. In addition, the status vectors estimated of the perturbation parameter including the position, velocity, and solar radiation pressure for the satellite are different before the start time and end time of orbital maneuvers, which means the same orbital parameters cannot be used for orbit integrations. Because the period of orbit maneuvering is unknown, the precise orbits of satellites cannot be determined during the non-maneuvering period. In order to adjust the strategy of precise orbit determination, the initial orbit and maneuver period must be determined. Therefore, it is necessary to develop an approach for detecting satellite orbit maneuvering periods with good time resolution. Recently, [PERSON] et al. presented a detection method to determine orbital maneuvers with the restored orbit calculated by broadcast ephemeris of BDS [11]. [PERSON] et al. determined orbit maneuvering by the root mean square of the orbit from the BeiDou satellites [12]. [PERSON] et al. detected orbital maneuvers by the orbit residual, which requires the known orbital maneuver dynamic models [13]. [PERSON] et al. used the mechanical energy difference of unit mass between space target and spacecraft to detect the orbital maneuver by the simulated data, and the effect of their method was restricted by the number of stations [14]. [PERSON] et al. determined orbit maneuvering by the orbit measurement data of the China Area Positioning System (CAPS), but the data is not available for the common users [15]. [PERSON] et al.