Session F2: Atmospheric Effects on GNSS

Analysis of GNSS Receiver Tracking During High-Latitude Ionospheric Scintillation
Andrew Ludwig and Xiaoqing Pi, Jet Propulsion Laboratory, California Institute of Technology

Data collected from Wide Area Augmentation System (WAAS) reference stations (WRS) in Alaska is analyzed to investigate GNSS loss of lock (LOL) events. While L-band amplitude or intensity scintillation rarely occurs in the auroral zone because of the spectral filtering effect (Pi et al., 2017), strong carrier phase scintillation can cause a receiver to lose lock. To understand and predict LOL events under scintillation conditions, it is desired to identify and measure the phase scintillation effect using GNSS data recorded by the reference receiver. For this purpose, measurements of the rate of TEC index (ROTI) are obtained using 1 Hz data from the WRS for 1-minute intervals, which characterize dual-frequency phase fluctuations caused by small-scale ionospheric irregularities. Such 1-minute ROTI measurements, or ROTI1m (hereafter), based on 1 Hz data are different from those made using 30-sec sampled data (Pi et al., 1997), the latter filtering out certain fluctuations in shorter periods. The receiver LOL events in and near the auroral zone are analyzed with ROTI1m data. Our dataset consists of four days of L1 and L2 carrier phase data from three WAAS reference stations, each station with three separate receiver antennas. All four days are during periods of geomagnetic storms and high ionospheric activity. We find evidence suggestive of a relation between ionospheric-induced phase perturbations and LOL at these high latitudes. In addition, we also look at amplitude scintillation events through the lens of S4c (Luo et al., 2020), and investigate their relation to the LOL events. We find very few instances of amplitude scintillation. It is also found that, interestingly, amplitude scintillation shows poor correlation between antennas separated by about 4 meters at the same site. As a result, we find no relation between amplitude scintillation and loss of lock in the data from these stations in and near the auroral zone.