Analysis of the scintillation characteristics on the different satellite links derived from GPS observations and SCINDA data over Mbarara

Abstract

Ionospheric scintillation is a frequent phenomenon over the low latitude regions. However, the severity of the scintillation on the various satellite-receiver links is a function of space and time. Therefore in satellite applications such as positioning, messages on satellite to ground links that are not affected by scintillation should be used. In this paper we present the statistics of scintillation on the accessible satellite links over Mbarara for the period 2011 to 2017. We used scintillation indices from the Scintillation Network Decision Aid (SCINDA) at Mbarara (Geographic coordinate -0.62°N, 30.66°E, and dip latitude -9.3°N) together with a proxy for amplitude scintillation derived from the carrier-to-noise ratio observable on the L1 frequency of the multi-frequency GPS receiver at Mbarara (Geographic coordinate -0.60°N, 30.74°E, and dip latitude -10.2°N) to characterise scintillation on different satellite links. The results showed that the proxy closely relate to amplitude scintillation index S4. Based on the proxy and the scintillation indices, both amplitude and phase scintillation over Mbarara peaks from 20:00–22:00 LT. Scintillation climatology shows equinoctial asymmetry with more frequent scintillation during autumnal equinox than vernal equinox. The spatial scintillation characteristics show that scintillation over Mbarara is directional with the most active regions in the azimuth range of $\sim$150° to $\sim$210°. The most affected links were for GPS satellites designated by the Pseudo Random Noise (PRN) number as PRN 31 and PRN 25 for amplitude and phase scintillation respectively, and the least affected by both phase and amplitude scintillation were PRN 5 and PRN 17. Based on these observations, we suggest that data from PRN 31 and PRN 25 be used with caution for satellite applications over Mbarara especially during times of scintillation.