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Politecnico di Torino, Torino, Italy
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- PublicationOpen AccessFirst Observations of GNSS Ionospheric Scintillations From DemoGRAPE Project(2016)
; ; ; ; ; ; ; ; ; ; ; ; ;; ; ; ; ; ; ; ;The Istituto Nazionale di Geofisica e Vulcanologia leads an international project funded by the Italian National Program for Antarctic Research, called Demonstrator of Global Navigation Satellite System (GNSS) Research and Application for Polar Environment (DemoGRAPE), in partnership with Politecnico di Torino, Istituto Superiore Mario Boella, and with South African National Space Agency and the Brazilian National Institute of Space Physics, as key collaborators. DemoGRAPE is a new prototype of support for the satellite navigation in Antarctica. Besides the scientific interest, the accuracy of satellite navigation in Antarctica is of paramount importance since there is always the danger that people and vehicles can fall into a crevasse during a snowstorm, when visibility is limited and travel is restricted to following specified routes using satellite navigation systems. The variability of ionospheric delay and ionospheric scintillation are two of the primary factors which affect the accuracy of satellite navigation. The project will provide a demonstrator of cutting edge technology for the empirical assessment of the ionospheric delay and ionospheric scintillations in the polar regions. The scope of the project includes new equipment for the recording and dissemination of GNSS data and products installed at the South African and Brazilian bases in Antarctica. The new equipment will facilitate the exchange of software and derived products via the Cloud computing technology infrastructure. The project portal is accessible at www.demogrape.net. We report the first Global Navigation Satellite System (GNSS) signal scintillations observed in Antarctica.356 101 - PublicationOpen AccessOn estimating the phase scintillation index using TEC provided by ISM and IGS professional GNSS receivers and machine learning(2024)
; ; ; ; ; ; ; ; ; Amplitude and phase scintillation indexes (S4 and SigmaPhi) provided by Ionospheric Scintillation Monitoring (ISM) receivers are the most used GNSS-based indicators of the signal fluctuations induced by the presence of ionospheric irregularities. These indexes are available only from ISM receivers which are not as abundant as other types of professional GNSS receivers, resulting in limited geographic distribution. This makes the scintillation indexes measurements rare and sparse compared to other types of ionospheric measurements available from GNSS receivers. Total Electron Content (TEC), on the other hand, is an ionospheric parameter available from a wide range of multi-frequency GNSS receivers. Many efforts have worked on establishing scintillation indicators based on TEC, and geodetic receivers in general, introducing various metrics, including the Rate of TEC change (ROT) and ROT Index (ROTI). However, a possible relationship between TEC and its variation, and the corresponding scintillation index that an Ionospheric Scintillation Monitor (ISM) receiver would estimate is not trivial. In principle, TEC can be retrieved from carrier phase measurements of the GNSS receiver, as . We investigate how to estimate SigmaPhi from time series of TEC and ROT measurements from an ISM in Ny-Ålesund (Svalbard) using Machine Learning (ML). To evaluate its usability to estimate SigmaPhi from geodetic receivers, the model is tested using TEC data provided by a quasi-co-located geodetic receiver belonging to the International GNSS Service (IGS) network. It is shown that the model performance when TEC from the IGS receiver is used gives comparable results to the model performance when TEC from the ISM receiver is utilised. The model's ability to infer the exact value of the scintillation index is bound to Mean Square Error (MSE) = 0.1 radians^2 when SigmaPhi < 0. 8 radians. For SigmaPhi > 0. 8 radians the MSE reaches 0.18 and 0.45 radians^2 in operative testing using ISM and IGS measurements, respectively. However, the model’s ability to detect phase scintillation from IGS TEC measurements is comparable to expert visual inspection. Such a model has potential in alerting against phase fluctuations resulting in enhanced SigmaPhi, especially in locations where ISM receivers are not available, but other types of dual-frequency GNSS receivers are present.150 18 - PublicationOpen AccessEffects of Phase Scintillation on the GNSS Positioning Error During the September 2017 Storm at SvalbardIn early September 2017, several space weather events triggered disturbed conditions of the near-Earth space. The combination of two coronal mass ejection arrivals, associated with an X-class flare, caused a strong geomagnetic storm on 7 and 8 September, thus inducing diffuse ionospheric phase scintillations on Global Navigation Satellite System (GNSS) signals. This work analyzes the effects and the actual impact of such phase scintillations on transionospheric Global Positioning System (GPS) signals and on related positioning accuracy. The research focuses in particular on high-latitude GPS L1 data, recorded during a test campaign in Svalbard, Norway. The joint effect of satellites at low elevation and the exposure of ionosphere to the geospace forcing make navigation a critical task for such a challenging environment. Data analysis shows that the performance of carrier smoothing algorithms was affected by the presence of moderate and strong phase scintillation. It is shown in this study that positioning errors double when GPS signals affected by scintillation are used. This work shows that scintillations induce a considerable clustering effect on the smoothed positioning solutions; therefore, a methodology to automatically and autonomously detect the boundaries of the scintillation event is suggested according to such an high-level effect. The use of software-defined radio receivers for automatically capturing and processing GNSS data affected by scintillation is an added value to the analysis, as it offers the possibility to implement advanced signal processing techniques and a deeper observation of the impact of scintillations on the signals.
90 44 - PublicationOpen AccessAnalysis of the ionospheric scintillations during 20-21 January 2015 from SANAE by means of the DemoGRAPE scintillation receivers(2017-08-19)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; This paper presents ionospheric scintillation data recorded at SANAE in Antarctica during a moderate geomagnetic storm on 20-21 January 2016 which gives evidence of the advantages of the new generation of instrumentation for monitoring ionospheric scintillation. The data was collected as part of the DemoGRAPE project aimed at the demonstration of cutting edge technology for the empirical assessment of the ionospheric delay and ionospheric scintillations in the polar regions which affect the accuracy of satellite navigation.164 110 - PublicationOpen AccessAnalysis and Characterization of an Unclassified RFI Affecting Ionospheric Amplitude Scintillation Index Over the Mediterranean Area(2023-04-13)
; ; ; ; ; ; ; Radio frequency (RF) signals transmitted by Global Navigation Satellite Systems (GNSSs) are exploited as signals of opportunity in many scientific activities, ranging from sensing waterways and humidity of the terrain to the monitoring of the ionosphere. The latter can be pursued by processing the GNSS signals through dedicated ground-based monitoring equipment, such as the GNSS Ionospheric Scintillation and Total Electron Content Monitoring (GISTM) receivers. Nonetheless, GNSS signals are susceptible to intentional or unintentional RF interferences (RFIs), which may alter the calculation of the scintillation indices, thus compromising the quality of the scientific data and the reliability of the derived space weather monitoring products. Upon the observation of anomalous scintillation indices computed by a GISTM receiver in the Mediterranean area, the study presents the results of the analysis and characterization of a deliberate, unclassified interferer acting on the L1/E1 GNSS signal bands, observed and captured through an experimental, software-defined radio setup. This article also highlights the adverse impacts of the interferer on the amplitude scintillation indices employed in scientific investigations, and presents a methodology to discriminate among regular and corrupted scintillation data.75 19 - PublicationOpen AccessInterpretation of microtremor 2D array data using Rayleigh and Love waves: the case study of Bevagna (central Italy)(2011-12)
; ; ; ; ; ; ;Puglia, R.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Milano-Pavia, Milano, Italia ;Tokeshi, K.; University of Western Sydney ;Picozzi, M.; German Research Centre For Geosciences, Potsdam, Germany ;D'Alema, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione CNT, Roma, Italia ;Parolai, S.; German Research Centre For Geosciences, Potsdam, Germany ;Foti, S.; Politecnico di Torino; ; ; ; ; In the last decades, geophysicists and seismologists have focused their attention on the inversion of empirical surface-waves’ dispersion curves from microtremor measurements for estimating the Swaves velocity structure at a site. This procedure allows a fast and convenient investigation without strong active sources, which are difficult to deploy especially in urban areas. In this study we report on a 2D seismic noise array experiment carried out at Bevagna (Central Italy) near the station BVG of the Italian Accelerometric Network (RAN). The site was investigated within the DPC-INGV S4 Project (2007-2009). The Rayleigh- and Love- waves dispersion characteristics were estimated using different methods. The inversion of the dispersion curves was then performed independently, obtaining two estimations for the S-waves velocity profiles. The results of cross-hole logging near the seismic station are used for a comparison. The shear waves velocity profiles estimated by microtremor analyses range up to 150m depth. The two independent procedures provide consistent shear waves velocity profiles for the shallow part of the model (20-30 m in depth) in agreement with the results of the cross-hole logging. Some problems arise between 30 and 40 m in depth in the profile estimated by surface waves. In this range cross-hole logging evidences an inversion of S-waves velocity. Although the cross-hole logging stops at 40 m of depth, we are confident about the results provided by the Rayleigh-waves analysis below 40-50 m. This case study suggests that greater efforts should be devoted to exploit the potential of a coupled analysis of Rayleigh and Love waves from microtremor array measurements.271 286 - PublicationRestrictedIonosphere Monitoring in South East Asia in the ERICA Study(2017)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; The ERICA study aims to find out signatures of the interplay between the magnetosphere‐geomagnetic field and the ionosphere that degrade trans‐ionospheric signals such as those transmitted by GNSS satellites. The project activity focuses on the characterization of the ionospheric variability of the Equatorial Ionospheric Anomaly in the South East Asian region through the analysis of datasets collected with an ad hoc measurements campaign. The campaign has been conducted with ground‐based instruments located in the footprints of the Equatorial Ionospheric Anomaly and Equatorial Ionospheric Trough. This paper presents some of the relevant results achieved by the project, in terms of ionospheric climatology and weather assessment over the interested area. In particular, the paper describes the average condition of the Equatorial Ionospheric Anomaly recorded during the entire campaign and provides interesting insights on relevant scintillation events.536 8 - PublicationRestrictedSoftware-defined radio technology for GNSS scintillation analysis: bring Antarctica to the labGlobal navigation satellite systems (GNSSs) are widely used to support logistics, scientific operations, and to monitor the polar ionosphere indirectly, which is a region characterized by strong phase scintillation events that severely affect the quality and reliability of received signals. Professional commercial GNSS receivers are widely used for scintillation monitoring; on the contrary, custom-designed solutions based on data grabbers and software receivers constitute novelty. The latter enables a higher level of flexibility and configurability, which is important when working in remote and severe environments. We describe the scientific, technological, and logistical challenges of installing an ionospheric monitoring station in Antarctica, based on a multi-constellation and multi-frequency GNSS data grabber and a software-defined radio receiver. Having access to the full receiver chain and to intermediate signal processing stages allows a deep analysis of the impact of scintillation and, in turn, a better understanding of the physical phenomenon. The possibility to process high-resolution raw intermediate frequency samples of the signal enables not only the computation of scintillation indexes with the same quality as professional devices but also the design and test of innovative receiver architectures and algorithms. Furthermore, the record and replay approach offers the possibility to process in the lab the signals captured on site, with high fidelity level. It is like being in Antarctica again, but with an unlimited set of receivers and higher computational, storage, and bandwidth resources. The main advantages and disadvantages of this approach are analyzed. Examples of monitoring results are reported, confirming the monitoring capabilities, showing the good agreement with commercial receiver outputs and confirming the validity of post-processing and re-play operations.
609 3 - PublicationOpen AccessFormation of ionospheric irregularities over Southeast Asia during the 2015 St. Patrickˈs Day storm(2016-12-29)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Spogli, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Cesaroni, C.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Di Mauro, D.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Pezzopane, M.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Alfonsi, Lu.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Musicò, E.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Povero, G.; Istituto Superiore Mario Boella ;Pini, M.; Istituto Superiore Mario Boella ;Dovis, F.; Politecnico di Torino ;Romero, R.; Politecnico di Torino ;Linty, N.; Politecnico di Torino ;Abadi, P.; National Institute of Aeronautics and Space LAPAN ;Nuraeni, F.; National Institute of Aeronautics and Space LAPAN ;Husin, A.; National Institute of Aeronautics and Space LAPAN ;Le Huy, M.; Institute of Geophysics Vietnam ;Thi Lan, T.; Institute of Geophysics Vietnam ;Vinh La, T.; University of Science and Technology, Hanoi, Vietnam ;Gil Pillat, V.; Universidade do Vale do Paraíba, São José dos Campos, Brazil ;Floury, N.; European Space Agency, Noordwijk, Netherlands; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ; We investigate the geospace response to the 2015 St. Patrickˈs Day storm leveraging on instruments spread over Southeast Asia (SEA), covering a wide longitudinal sector of the low-latitude ionosphere. A regional characterization of the storm is provided, identifying the peculiarities of ionospheric irregularity formation. The novelties of this work are the characterization in a broad longitudinal range and the methodology relying on the integration of data acquired by Global Navigation Satellite System (GNSS) receivers, magnetometers, ionosondes, and Swarm satellites. This work is a legacy of the project EquatoRial Ionosphere Characterization in Asia (ERICA). ERICA aimed to capture the features of both crests of the equatorial ionospheric anomaly (EIA) and trough (EIT) by means of a dedicated measurement campaign. The campaign lasted from March to October 2015 and was able to observe the ionospheric variability causing effects on radio systems, GNSS in particular. The multiinstrumental and multiparametric observations of the region enabled an in-depth investigation of the response to the largest geomagnetic storm of the current solar cycle in a region scarcely reported in literature. Our work discusses the comparison between northern and southern crests of the EIA in the SEA region. The observations recorded positive and negative ionospheric storms, spread F conditions, scintillation enhancement and inhibition, and total electron content variability. The ancillary information on the local magnetic field highlights the variety of ionospheric perturbations during the different storm phases. The combined use of ionospheric bottomside, topside, and integrated information points out how the storm affects the F layer altitude and the consequent enhancement/suppression of scintillations.571 881