Real-Time Detection of Ionospheric Scintillations and Potential Applications

Irma Rodríguez, Carlos Hernández, Ana Curiel, Carlos Catalán, Laura Fernández, Esther Sardón

Abstract:	One of the most important characteristics of any regional or global satellite navigation system providing integrity is the monitoring of the signals broadcast by the satellites by means of a network of stations and its propagation effects. Integrity implies the provision of timely alerts to the users, preventing them from the use of signals from satellites not working within the specifications. For most applications, users must receive these alerts in the order of a few seconds; consequently the analysis of the quality of the broadcast signals and the propagation effects has to be done in real-time. In the frame of the Galileo design, a new algorithmic approach for analyzing in real-time the carrier phase behavior in terms of measurement noise and stability has been established as part of the development of the IPF (Integrity Processing Facility), which is the element of the GMS (Ground Mission Segment) design and developed by GMV in charge of the computation of Galileo integrity message. One important source of degradation in the quality of the carrier phase measurements are the scintillations observed under strong ionospheric conditions. Such scintillations cause an increase in the number of cycle slips and a decrease in the Signal-to- Noise Ratio (SNR). In this context, the definition of a new algorithm aimed at detecting degraded ionospheric conditions has been imperative to improve the Galileo availability for users near the magnetic equator or near the poles and also to enhance the integrity monitoring, which would be strongly penalized if carrier phase measurements degraded by the presence of scintillations were not used by the integrity algorithms. The performances of the new algorithm have been tested under both nominal and degraded ionospheric conditions by processing real GPS data from a set of IGS (International GNSS Service) sensor stations worldwide distributed. In view of the obtained results, it can be confirmed that the new approach not only allows detecting and repairing cycle slips with high accuracy in nominal conditions, but also improves the robustness of the algorithm by detecting strong scintillations conditions in order to avoid using carrier phase measurements until the situation is recovered. The objective here is thus twofold: provide a description of the algorithms defined for the real-time repair of cycle slips and detection of scintillations, including the theoretical modeling and covariance analysis; and present the test campaign with real GPS data, together with the most relevant results.
Published in:	Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008) September 16 - 19, 2008 Savannah International Convention Center Savannah, GA
Pages:	277 - 288
Cite this article:	Rodríguez, Irma, Hernández, Carlos, Curiel, Ana, Catalán, Carlos, Fernández, Laura, Sardón, Esther, "Real-Time Detection of Ionospheric Scintillations and Potential Applications," Proceedings of the 21st International Technical Meeting of the Satellite Division of The Institute of Navigation (ION GNSS 2008), Savannah, GA, September 2008, pp. 277-288.
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