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Cafaro, Massimo
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Cafaro, Massimo
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- PublicationOpen AccessAdaptive Phase Detrending for GNSS Scintillation Detection: A Case Study Over Antarctica(2021)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; We aim at contributing to the reliability of the phase scintillation index on Global Navigation Satellite System (GNSS) signals at high-latitude. To the scope, we leverage on a recently introduced detrending scheme based on the signal decomposition provided by the fast iterative filtering (FIF) technique. This detrending scheme has been demonstrated to enable a fine-tuning of the cutoff frequency for phase detrending used in the phase scintillation index definition. In a single case study based on Galileo data taken by a GNSS ionospheric scintillation monitor receiver (ISMR) in Concordia Station (Antarctica), we investigate how to step ahead of the cutoff frequency optimization. We show how the FIF-based detrending allows deriving adaptive cutoff frequencies, whose value changes minute-by-minute. They are found to range between 0.4 and 1.2 Hz. This allows better accounting for diffractive effects in phase scintillation index calculation and provides a GNSS-based estimation of the relative velocity between satellite and ionospheric irregularities.812 66 - PublicationOpen AccessA measure of ionospheric irregularities: zonal velocity and its implications for L-band scintillation at low-latitudes(2021-10-22)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; We estimate the zonal drift velocity of small-scale ionospheric irregularities at low latitude by leveraging the spaced-receivers technique applied to two GNSS receivers for scintillation monitoring installed along the magnetic parallel passing in Presidente Prudente (Brazil, magnetic latitude 12.8°S). The investigated ionospheric sector is ideal to study small-scale irregularities, being located close to the expected position of the southern crest of the equatorial ionospheric anomaly. The measurement campaign took place between September 2013 and February 2014, i.e. equinox and summer solstice seasons under solar maximum, during which the probability of formation of small-scale irregularities is expected to maximize. We found that the hourly average of the velocity increases up to 135 m/s right after the local sunset at ionospheric altitudes and then smoothly decreases in the next hours. Such measurements are in agreement with independent estimations of the velocity made by the Incoherent Scatter Radar located at the Jicamarca Radio Observatory (magnetic latitude 0.1°N), by the Boa Vista Ionosonde (magnetic latitude 12.0°N), and by applying a recently-developed empirical regional short-term forecasting model. Additionally, we investigated the relationship with the percentage occurrence of amplitude scintillation; we report that it is exponentially dependent on the zonal velocity of the irregularities that cause it.670 92 - PublicationOpen AccessUser-Oriented ICT Cloud Architecture for High-Accuracy GNSS-Based Services(2019)
; ; ; ; ; ; ; ; ;; ;; ; We introduce a new information and communication technology (ICT) cloud-based architecture for Global Navigation Satellite System (GNSS) high-accuracy solutions, offering also a commercial overview of GNSS downstream market to show how the developed innovation is thought to fit in the real context. The designed architecture is featured by dynamic scalability, increased integrity, and greater agility of the ICT system. The novelty of the solution developed is a customized ICT architecture, obtained through unique and privileged access to user communities in the frame of the H2020 project TREASURE, allowing the development of a solution entirely driven by user needs. The economic outlook of GNSS downstream markets evolution highlights how the technology proposed effectively matches the evolving business environment, specifically in regard to the increasing need for flexibility and competitive advantage deriving from services. The simultaneous adoption of the technical and commercial perspective is meant to offer interesting findings to both the scientific community and GNSS industry, creating synergies previously unexplored.920 22 - PublicationOpen AccessGPS loss of lock statistics over Brazil during the 24th solar cycle(2020-04)
; ; ; ; ; ; ; ; ;; ;A statistical analysis of Loss of Lock (LoL) over Brazil throughout the 24th solar cycle is performed. Four geodetic GPS dual-frequency (L1, L2) receivers, deployed at different geographic latitudes ranging from about 25° to 2° South in the eastern part of the country, are used to investigate the LoL dependence on time of the day, season, solar and geomagnetic activity. The results of the analysis show that LoL is most likely in the post-sunset hours during summer and equinox, especially within the southern crest of the Equatorial Ionospheric Anomaly (EIA), in a region between about 10°S and 25°S of geographic latitude, matching the typical behaviour of scintillation over Brazil. This is confirmed by the correlation found between the relative occurrence of LoL (LoL (%)) and the Rate Of TEC Index (ROTI), used as a proxy of scintillation index and calculated for each receivers along the entire period of investigation. The LoL (%) for given solar and geomagnetic indices show some correlation with increasing the severity of the index. This correlation is strongest in the area of the southern crest of the EIA, while there is little to no apparent impact closer to the equator, depending on the index. LoL (%) increases with increasing geomagnetic disturbances, varying between ~1% and ~10% for AE ranged between 400 and 1200 nT, and exceeding 3% when Dst is around −100 nT, both related to moderate-severely disturbed conditions.267 143 - PublicationOpen AccessDisentangling ionospheric refraction and diffraction effects in GNSS raw phase through fast iterative filtering technique(2020-06-29)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; We 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 (FIF) signal decomposition technique, which is a recently developed fast implementation of the well-established Adaptive Local Iterative Filtering (ALIF) algorithm. FIF has been conceived to decompose nonstationary signals efficiently and providing 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 SigmaPhi index. We found values of cutoff frequency in the range of 0.73 to 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.1163 54 - PublicationOpen AccessMulti-instrumental analyses of the September 2017 space weather storm over Brazil(2019-03-09)
; ; ; ; ; ; ; ; ; Brazil is a region of the Earth daily affected by strong ionospheric variability that may exacerbate during space weather events. In this paper, the ionospheric response to the solar storms that occurred in the first half of September 2017 is analyzed in terms of scintillation and TEC data from ground-based GNSS, ionospheric parameters from ionosondes and in-situ electron density data provided by the ESA Swarm mission. The result shows the complexity of the equatorial ionospheric dynamics under severe geospatial perturbations highlighting the occurrence of a super fountain event during daytime as the effect of a severe geomagnetic storm.80 19