A two-step method to detect broadcast ephemeris unavailable periods caused by BeiDou satellite orbital maneuvers

The space constellation of the BeiDou navigation satellite system(BDS) is a hybrid constellation containing medium earth orbit(MEO) satellites, geostationary earth orbit(GEO) satellites, and inclined geosynchronous orbit(IGSO) satellites. Due to the geosynchronous characteristics of GEO and IGSO, GEO satellites and IGSO satellites often need to perform orbital maneuvers, which can affect the signal-inspace(SIS) availability performance of BeiDou satellites. A two-step detection method for BeiDou satellite orbital maneuvers has been proposed in this paper. The first step is to identify orbital maneuvers based on time series analysis of broadcast ephemeris, and the second step is to verify orbital maneuvers based on bidirectional orbit prediction. The two-step detection method was used to detect the orbital maneuvers of BeiDou satellites in 2019. Through the double guarantees of identification and verification,the detection accuracy of BeiDou satellite orbital maneuvers has been effectively improved. And the orbital maneuver detection results are continued to be used to assess the SIS availability of BeiDou satellites. The results show that the availability loss of GEO satellite orbital maneuvers is about 0.45%-1.07%, and the availability loss of IGSO satellite orbital maneuvers is about 0.12%-0.19%.

Recover the abnormal positioning,velocity and timing services caused by BDS satellite orbital maneuvers

The BeiDou Navigation Satellite System(BDS)provides global Positioning,Velocity,And Timing(PVT)services that are widely used in various areas.The BDS satellites frequently need the orbit maneuvers due to various perturbations to keep satellites in their designed positions.During these maneuvers,PVT services may be abnormal if the data from a maneuvering satellite is used.In this paper we developed an approach to recover the abnormal PVT services.By using BDS observations from multiple tracking stations,the orbital errors of a maneuvering satellite can be in real time obtained and corrected,thereby avoiding any influence on the performance of PVT services.The tests show that the average precision of position,velocity and timing services are improved by 0.8 m,0.1 mm/s and 0.16 ns,respectively,using the developed orbital maneuver recovery approach.In addition,the approach can also be used for the orbital maneuver detection and monitoring.

Optimal maneuvering strategy of spacecraft evasion based on angles-only measurement and observability analysis

Spacecraft orbit evasion is an effective method to ensure space safety. In the spacecraft’s orbital plane, the space non-cooperate target with autonomous approaching to the spacecraft may have a dangerous rendezvous. To deal with this problem, an optimal maneuvering strategy based on the relative navigation observability degree is proposed with angles-only measurements. A maneuver evasion relative navigation model in the spacecraft’s orbital plane is constructed and the observability measurement criteria with process noise and measurement noise are defined based on the posterior Cramer-Rao lower bound. Further, the optimal maneuver evasion strategy in spacecraft’s orbital plane based on the observability is proposed. The strategy provides a new idea for spacecraft to evade safety threats autonomously. Compared with the spacecraft evasion problem based on the absolute navigation, more accurate evasion results can be obtained. The simulation indicates that this optimal strategy can weaken the system’s observability and reduce the state estimation accuracy of the non-cooperative target, making it impossible for the non-cooperative target to accurately approach the spacecraft.

Effectiveness-based orbital optimization for servicing spacecraft

Effectiveness-based system development is an essential technology developing concept advanced by some countries,such as the U.S.A.Making use of Analytic Hierarchy Process,this paper brings forward a methodology for orbital optimization based on effectiveness in the case of the orbital deployment for the Servicing Spacecraft(SSC),which needs to accomplish many types of tasks and whose orbit is affected by kinds of factors with contradictions in orbital parameter selection.Firstly,the possible tasks of SSC are decomposed and their degrees of importance are given by the times,probabilities,values of their applications.Then,the supporting capabilities are discussed from the viewpoint of orbit design,and the determination of their weights is put forward.Finally,the relationships between the orbital parameters and the effectiveness are established by using effective function,and three synthesizing methods for a single task and its capabilities are presented.