Ionospheric scintillation characteristics in IRNSS L5 and S-band signals

Abstract

Ionospheric scintillation is a common phenomenon observed over the low latitude Indian region. It occurs due to the rapid fluctuations in phase and amplitude of the signal and affects Global Navigation Satellite Systems (GNSS) very severely, especially in L-band. Severe scintillation leads to loss of lock at the receiver, which affects user position accuracy. Ionospheric scintillation mainly depends on solar cycle, user latitude, local time, season and elevation angle of the satellite. It also depends on the frequency of the transmitted signal. Usually, lower frequencies experience higher scintillation at ionosphere. In this paper, ionospheric amplitude scintillation effect on Indian Regional Navigation Satellite System (IRNSS) L5 and S-band frequencies is studied on the basis of computed S4 index from Carrier to Noise (C/No) ratio measurements from IRNSS receivers installed at New Delhi and Ahmedabad. A comparison of L5 and S-band scintillation is done. A confirmation of scintillation phenomenon is also carried out using co-located GPS Septentrio (PolarRxS REO) receiver at frequency L1. It is, further, found that the scintillation occurrence is mostly in post sunset periods and may result in frequent loss of lock at L5 band during these periods.