Abstract
The BeiDou system satellites may be unhealthy due to many reasons, affecting system performance in different ways. Therefore, it is important to analyze the causes and characteristics of the satellites’ unhealthy states. In this study, these states are classified into five types based on the broadcast ephemeris. Three criteria are presented, based on which a general classification method is proposed. Data from July 2017 to June 2018 are analyzed to validate the method, from which we know that the average unhealthy duration due to satellite maneuvers is much longer than the duration of unhealthy states related to satellite orbit or clock anomalies, and the other unhealthy states may be caused by inbound or outbound satellites. Statistics show that most of the time, the number of unhealthy satellites is no more than two and the average positioning accuracy in the service area will decrease by no more than 0.75 and 1.2 meters when one or two BDS satellites are unhealthy, respectively.
Highlights
Satellites will not stay in their predefined orbits all the time, since there are many unwanted perturbations in the environment [1,2]
Compared to medium Earth orbit (MEO) satellites, geostationary orbit (GEO) and inclined geosynchronous orbit (IGSO) satellites suffer more from this issue
Satellite unhealthy states caused by other factors are not well studied and categorized, and to the authors’ knowledge their influence on BeiDou System (BDS) service performance is not known, which is the foremost concern of this paper
Summary
Satellites will not stay in their predefined orbits all the time, since there are many unwanted perturbations in the environment [1,2]. The methods can efficiently distinguish maneuvers and orbit anomalies by comparing satellite positions at the same epoch calculated with ephemerides of different reference times [14,15]. Huang et al presented a maneuver and anomaly detection method by comparing the modified pseudo-range and the geometric distance calculated with broadcast ephemeris and receiver position [16,17] This method is like the receiver autonomous integrity monitoring (RAIM) technique and can detect one satellite anomaly in real time. Satellite unhealthy states caused by other factors are not well studied and categorized, and to the authors’ knowledge their influence on BDS service performance is not known, which is the foremost concern of this paper. The influence of unhealthy BDS satellites on service performance is analyzed, providing a reference for BDS operation and management
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