Satellite Integrity Autonomous Monitoring (SAIM) of BDS and Onboard Performance Evaluation

Abstract

With the development of satellite navigation technology, the users’ demands for the integrity of GNSS are more and more intense. The ground based monitoring system can hardly report an alarm message to the GNSS users during the valid alarming period due to the satellite-earth propagation delay. It is beneficial to monitor the abnormal events and report the corresponding alarms in orbit. Through this way, which is an important branch of the future GNSS integrity monitoring, the time needed to give an alarm is shorter and the capability of system integrity service is strengthened. A new generation of BDS satellites has the capable of satellite autonomous integrity monitoring (SAIM). This paper presents the technology scheme of SAIM, and proposes the integrity monitoring method of navigation signals and clock on-board. The proposed method is verified based on the onboard test of the IGSO satellite. In addition, we analyze the integrity telemetry data from the new generation of BDS satellite, including the signal delay, power, carrier phase measurement, correlation peak, consistency of pseudo-code and carrier phase, clock phase and frequency step. The analysis results indicate that the quality of the data on orbit meets the requirements, and SAIM could monitor effectively the abnormal change of satellite clock and navigation signal, generate rapidly the alarm message, and transmit them to user. The alarm time is less than 6 s through the message, and 2 s through the non-standard code (NSC). In the end, we present the future work for improving the SAIM technology of BDS.