Chevalier, Jean-Marie ; Bergeot, Nicolas ; Marqué, Christophe ; Bruyninx, Carine

Talk presented at ESWW13, Ostende, Belgium on 2016-11-15

Abstract: Intense solar radio bursts (SRBs) emitted at L-band frequencies can affect the carrier-to-noise density C/N0 of Global Navigation Satellite Systems (GNSS) signals by increasing the background noise. Such space weather events can consequently decrease the quality of GNSS-based results especially for kinematic high-precision positioning. Although solar observatories monitor the solar radio emissions, their direct impacts at the GNSS frequencies are not determined in real-time. For this purpose, we developed at the Royal Observatory of Belgium (ROB) a method capable to detect SRBs based on real-time C/N0 observations from a regional GNSS (GPS+GLONASS) network. First, S1 and S2 raw data extracted from RINEX files were converted when necessary into the C/N0 unit (dB.Hz) taking into account manufacturer corrections. Then, the differences (∆C/N0) between these C/N0 observables and their medians of the 7 previous satellite ground track repeat cycles, i.e. their normal quiet state, were computed to remove the repeatable patterns (satellite elevation and multipath). Finally, the median <∆C/N0> from the regional GNSS network allows detecting and quantifying the impact of a SRB on GNSS signals quality at each frequency (i.e. L1 and L2). To validate this method, we investigated the degradation of GPS and GLONASS C/N0 on the entire EUREF Permanent Network (EPN) during 11 intense SRBs occurring between 1999 and 2015. The analysis shows that: (1) GPS and GLONASS ∆C/N0 agree at the 0.1±0.2dB.Hz level; (2) the standard deviation of the <∆C/N0> at L1 and L2 are stable and below 1dB.Hz 96% of the time; the least intense SRB was detected with 1 dB.Hz <∆C/N0> fade and the most intense SRB reached a <∆C/N0> fade of 12 dB.Hz; (3) maximum ∆C/N0 degradation occurs at the maximum solar peak flux delivered by the solar ground observatories; (4) C/N0 degradation becomes larger with increasing solar zenithal angle. Consequently, the degradation of GNSS signal reception due to SRBs over Europe is now monitored at ROB in near real-time. With this new method, the SRB of the 4th November 2015 was already highlighted at the GNSS L2 frequency. In addition, first results of the method tested into other regions (Africa and South America) using the real-time network of the IGS will be introduced.