Innovative contributions to ionospheric scintillation monitoring using GNSS observations
(English) Ionospheric scintillation adversely impacts Global Navigation Satellite System (GNSS) receivers by inducing signal amplitude fading and rapid carrier phase variations, degrading positioning accuracy in regions with high ionospheric activity. Monitoring scintillation is essential for ensuri...
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| Formato: | tesis doctoral |
| Estado: | Versión publicada |
| Fecha de publicación: | 2025 |
| País: | España |
| Recursos: | CBUC, CESCA |
| Repositorio: | TDR. Tesis Doctorales en Red |
| OAI Identifier: | oai:www.tdx.cat:10803/693978 |
| Acesso em linha: | http://hdl.handle.net/10803/693978 https://dx.doi.org/10.5821/dissertation-2117-425935 |
| Access Level: | acceso abierto |
| Palavra-chave: | Geodetic detrending (GD) Global Navigation Satellite System (GNSS) ionosphere low cost rate of total electron content index (ROTI) real time (RT) scintillation Àrees temàtiques de la UPC::Enginyeria de la telecomunicació Àrees temàtiques de la UPC::Aeronàutica i espai 52 - Astronomia. Astrofísica. Investigació espacial. Geodèsia 621.3 - Enginyeria elèctrica. Electrotècnia. Telecomunicacions |
| Resumo: | (English) Ionospheric scintillation adversely impacts Global Navigation Satellite System (GNSS) receivers by inducing signal amplitude fading and rapid carrier phase variations, degrading positioning accuracy in regions with high ionospheric activity. Monitoring scintillation is essential for ensuring the reliability of GNSS applications, particularly in precise positioning. Scintillation monitoring traditionally relies on two indices, the amplitude scintillation index $S_4$ and the phase scintillation index $\sigma_\varphi$, both typically derived from specialized GNSS receivers known as ionospheric scintillation monitoring receivers (ISMRs). However, the high cost of ISMRs limits their global deployment. Recently, geodetic receivers operating at 1 Hz have been proposed as alternatives for monitoring scintillation, benefiting from existing global GNSS networks. Despite their potential, geodetic receivers face challenges in scintillation monitoring due to their less stable clocks, which contaminate monitoring results. A common method for addressing this is the use of rate of total electron content index (ROTI), which utilizes the geometry-free combination of dual-frequency signals (e.g., GPS L1 and L2) to eliminate the non-dispersive effects. Despite this, this classical ROTI still has drawbacks, such as the dependence on receiver-specific tracking strategies for L2 signal and the frequent cycle-slips (CSs) in L2 measurements, undermining reliable monitoring. In recent years, the Geodetic Detrending (GD) technique has been developed to offer a promising solution by modelling individual GNSS carrier phase measurements to derive $\sigma_\varphi$ index from uncombined L1 signals. This technique achieves full consistency with ISMR results, offering a novel perspective on scintillation monitoring using geodetic receivers. This research addresses key challenges in scintillation monitoring using GD as the primary methodology. First, a novel $\mathrm{ROTI_{L1}}$ index was introduced, calculated from uncombined L1 signals using GD. $\mathrm{ROTI_{L1}}$ exhibits minimal dependence on receiver models or tracking strategies, making it a robust candidate for consistent global scintillation monitoring. Analysis of data from 2020 established a minimum detectable scintillation threshold of 1.8 TECU/min for $\mathrm{ROTI_{L1}}$ over 60-s intervals with 1-Hz observations. Second, low-cost receivers, such as the Septentrio Mosaic-X5 and UBLOX ZED-F9P, were evaluated for their feasibility in scintillation monitoring, addressing challenges in deploying geodetic-grade receivers in uncovered or high-risk regions. These devices, costing approximately less than one-tenth of geodetic receivers, demonstrated comparable performance using GD. Additionally, noise levels of these receivers were assessed, and thresholds for detecting scintillation using $S_4$ and $\sigma_\varphi$ indices were determined. Third, the growing demand for time-sensitive GNSS applications requires real-time (RT) scintillation monitoring. To address this, the GD technique was extended for RT processing using RT satellite corrections and observations. A prototype RT GD framework was developed to deliver the scintillation indices in a global scale. Validation studies, including comparisons with post-processing results and data from a collocated ISMR, demonstrated its high reliability. The RT monitoring products of the $\sigma_\varphi$ index are now publicly accessible, making it valuable for both scientific research and industrial applications. In conclusion, this research advances scintillation monitoring by offering a solution that is accurate, cost-effective, and capable of extensive coverage. These contributions have the potential to enhance GNSS performance under challenging ionospheric conditions. |
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