Triple-Frequency GNSS Cycle Slip Detection Performance in the Presence of Diffractive Ionosphere Scintillation

摘要

Ionosphere scintillation is notorious for causing some of the most severe disturbances in GNSS measurements. This phenomenon occurs when radio signals that propagate through ionosphere plasma irregularities exhibit strong phase and amplitude fluctuations. Scintillation near the equator, in particular, is associated with diffractive signal fluctuations that contain deep fades in signal amplitude and associated fast phase changes and cycle slips. Ionosphere diffraction-induced cycle slips challenge traditional methods of cycle slip mitigation, which all assume cycle slips occur instantaneously between measurement epochs and do not account for large phase measurement fluctuations. In this work, we present an example of strong diffractive scintillation affecting a triple-frequency GPS satellite. We apply detrending to ionosphere-free phase combinations of very high-rate (100 Hz) carrier phase measurements and use these to manually estimate cycle slip amplitudes. We then look at single-epoch time-differenced cycle slip correction algorithm from [1] and quantify its effectiveness when applied to strong equatorial scintillation that exhibits diffraction. Ultimately, this work serves to document how cycle slip algorithms behave and what are their limits under degraded-signal conditions such as during diffractive ionosphere scintillation.