How modernized and strengthened GPS signals enhance the system performance during solar radio bursts

A Solar Radio Burst (SRB) is one of the most severe natural hazards affecting the performance of the global navigation satellite systems (GNSS). Considering the influence of different threat factors, the GNSS developers upgrade the systems to amend the accuracy and noise-proof features of the systems. In particular, GPS gradually replaces “old” satellites (GPS IIA, GPS IIR-A, GPS IIR-B) with new-generation equipment (GPS IIR-M, GPS IIF, GPS III) featured by an increase in the emitted signal power at L2 frequency and by new civilian codes. In this work, based on examples of the extreme SRB of September 24, 2011, and the severe SRB of September 6, 2017, we study how such modernization can improve the GPS system performance during solar flares accompanied by intense SRB. We recorded SRB-related drops in signal strength (S), which were 7.5/0 dB-Hz for the S1C, 10/7 dB-Hz for the S2X, 17/8 dB-Hz for the S2W and 9/7.5 for the S5/S5X in 2011/2017 correspondingly. The drop in the S2W signal strength for the modernized blocks was comparable in amplitude to those of the “old” blocks. However, the modernized IIR-M/IIF blocks were featured by about 5 dB-Hz higher signal strength. This resulted in a double and triple decrease in loss-of-lock density for the IIR-M/IIF satellites in 2011 and 2017, respectively, as compared to IIA/IIR-A during SRBs. Therefore, the increase in the emitted signal power and new civilian codes potentially enhance the stability of the GPS operation.