On the accuracy of the GPS L2 observable for ionospheric monitoring
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The introduction of the unencrypted global positioning system (GPS) L2 civil (L2C) signal has the potential to improve measurements made with the L2 frequency, an important observable in GPS-based ionospheric research and monitoring. Recent work has shown significant differences between the legacy L2P(Y) and L2C-derived total electron content rate of change index (ROTI). This difference is observed between L2P(Y) and L2C-derived ROTI with certain receiver models and between zero-baseline receiver pairs. We discuss the likely cause for these differences: L1-aided tracking used to track both the L2P(Y) and L2C signals. We also present L2C data that are confirmed to be from tracking independent of L1. Using the ionospheric-free linear combination, we show that the independently tracked carrier phase dynamics are significantly more accurate than the L1-aided observables. This result is confirmed by comparing the behavior of the L2C and L2P(Y) carrier phase observables upon a sudden antenna rotation.
KeywordsIonosphere Global positioning system (GPS) Total electron content (TEC) Rate of change of TEC index (ROTI) L2 civil signal GPS tracking
CHAIN infrastructure funding was provided by the Canadian Foundation for Innovation and the New Brunswick Innovation Foundation. CHAIN operation is conducted in collaboration with the Canadian Space Agency. The data used can be obtained by contacting CHAIN directly. We thank the J. R. Armstrong Family Foundation for funding the presented research. Jayachandran and Langley are also supported by the Natural Sciences and Engineering Research Council of Canada.
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