A New System for the Detection and Monitoring of Carrier Phase Anomalies in the GPS Constellation

Aaron Kerkhoff, Johnathan York, Scotland Nelsen, Otto Caldwell, David Munton, Thomas Garcia, Michael Bratton

Abstract:	A new system for the detection and continuous monitoring of GPS signal anomalies is presented. The anomaly detection system is based on the High Rate Tracking Receiver (HRTR) software-defined radio (SDR) receiver platform, which provides a multi-channel tracking capability for all civil GPS signals on the L1, L2 and L5 frequencies. The current focus of the system is for detection of excursions in the carrier phase transmitted by GPS satellites. High rate post-correlation and tracking data from the HRTR are combined to detect carrier phase variations at a rate of up to 1 kHz. This data is used to calculate a metric based upon the Modified Allan Variance to detect step-like carrier phase anomalies typical of GPS satellite transmissions. Upon detection, information about the anomaly is recorded and ultimately archived in a database, which can be used for long-term analysis of anomaly behavior; additionally a short sample of raw data is recorded for each anomaly to aid post-analysis. The design of the anomaly detection system as well as the detection processing approach are described. Results from one year of operation of the system are presented. This includes summary statistics of anomaly behavior across the GPS constellation as well as multiple examples of detected anomalies. Results and discussion are also provided regarding the impact of these anomalies on traditional GPS receivers.
Published in:	Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014) September 8 - 12, 2014 Tampa Convention Center Tampa, Florida
Pages:	3542 - 3553
Cite this article:	Kerkhoff, Aaron, York, Johnathan, Nelsen, Scotland, Caldwell, Otto, Munton, David, Garcia, Thomas, Bratton, Michael, "A New System for the Detection and Monitoring of Carrier Phase Anomalies in the GPS Constellation," Proceedings of the 27th International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS+ 2014), Tampa, Florida, September 2014, pp. 3542-3553.
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