Disentangling ionospheric refraction and diffraction effects in GNSS raw phase through fast iterative filtering technique

• Published in: GPS Solutions
• Main Authors: Claudio Cesaroni, Lucilla Alfonsi, Luca Spogli, Hossein Ghobadi, Nicola Linty, Massimo Cafaro, Antonio Cicone, Vincenzo Romano
• Format: Article in Journal/Newspaper
• Language: English
• Published: 2020
• Subjects: H2020; European Training Networks; EC; European Commission; Knowmad Institut; General Earth and Planetary Sciences; H2020 Marie Skłodowska-Curie Actions; Concordia Station; Antarc*; Antarctica
• Online Access: https://www.openaccessrepository.it/record/80197; https://doi.org/10.1007/s10291-020-01001-1

AbstractWe contribute to the debate on the identification of phase scintillation induced by the ionosphere on the global navigation satellite system (GNSS) by introducing a phase detrending method able to provide realistic values of the phase scintillation index at high latitude. It is based on the fast iterative filtering signal decomposition technique, which is a recently developed fast implementation of the well-established adaptive local iterative filtering algorithm. FIF has been conceived to decompose nonstationary signals efficiently and provide a discrete set of oscillating functions, each of them having its frequency. It overcomes most of the problems that arise when using traditional time–frequency analysis techniques and relies on a consolidated mathematical basis since its a priori convergence and stability have been proved. By relying on the capability of FIF to efficiently identify the frequencies embedded in the GNSS raw phase, we define a method based on the FIF-derived spectral features to identify the proper cutoff frequency for phase detrending. To test such a method, we analyze the data acquired from GPS and Galileo signals over Antarctica during the September 2017 storm by the ionospheric scintillation monitor receiver (ISMR) located in Concordia Station (75.10° S, 123.33° E). Different cases of diffraction and refraction effects are provided, showing the capability of the method in deriving a more accurate determination of the $$\sigma_{\phi }$$ σ ϕ index. We found values of cutoff frequency in the range of 0.73–0.83 Hz, providing further evidence of the inadequacy of the choice of 0.1 Hz, which is often used when dealing with ionospheric scintillation monitoring at high latitudes.