Feasibility of scintillation monitoring with low-cost GNSS receivers using geodetic detrending

The geodetic detrending (GD) methodology was introduced in the past decade and has opened the door to the global monitoring of ionospheric scintillation using global navigation satellite system (GNSS) receivers. The performance of GD has been demonstrated in geodetic receivers. However, extending scintillation monitoring to low-cost commercial receivers remains a challenge. Low-cost devices could serve as valuable complements to specialised and much more expensive scintillation monitoring receivers. In this paper, first, a feasibility study was conducted using the GD technique, demonstrating that the scintillation indices derived from the observations of two low-cost receivers (Septentrio Mosaic X5 and UBLOX ZED-F9P) have a resolution similar to that achieved by geodetic receiver models, whose price is one order of magnitude higher. Second, measurements of GNSS signals at different frequencies from the Galileo and global positioning system (GPS) satellites were analysed in a specific experiment over six days of null scintillation. Next, the noise level in the scintillation parameters derived from the experiment was evaluated, which shows that for low-cost receivers, the minimum scintillation detection threshold increases only negligibly compared to geodetic-grade receivers. Moreover, the geometry-free (GF) combination of L1 with a second signal of different frequency was investigated as an alternative to detrending GNSS signals. Finally, for determining the ionospheric fluctuations produced by scintillation, the limitations of using the GF combination versus the uncombined measurements were highlighted. It is concluded that the minimum resolution of scintillation indices derived from low-cost receiver measurements makes it possible to distinguish values associated with periods of scintillation activity from those produced by residual noise from mismodeling. For both geodetic and low-cost receivers, the scintillation detection threshold obtained with uncombined carrier-phase measurements is smaller than that achieved with the classic GF combination.