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Linty, Nicola
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Linty, Nicola
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- 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 - 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 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 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.356 102 - 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 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 - PublicationOpen AccessInstallation and configuration of an ionospheric scintillation monitoring station based on GNSS receivers in AntarcticaGlobal Navigation Satellite Systems (GNSSs), such as the US Global Positioning System (GPS), The Russian GLONASS or the European Galileo, are space-based navigation systems. GNSSs enable a generic user located anywhere on the Earth to determine in real time his Position, Velocity and Time (PVT), by means of a Radio Frequency (RF) electro-magnetic signal, the Signal-In-Space (SIS), transmitted by a constellation of satellites orbiting around Earth. Uninterrupted Positioning, Navigation, and Timing (PNT) solution is determined by GNSS receivers, which continuously process the SIS from the satellites in view. GNSS receivers are part of the GNSSs ground segment. They are a suboptimal implementation of a maximum likelihood estimator of the SIS propagation time. The PNT solution is indeed based on the computation of the SIS Time Of Arrival (TOA), according to the satellite and receiver local clocks. This is achieved thanks to the presence of a different Pseudo Random Noise (PRN) spreading code in the modulated SIS broadcast by each satellite. In the GNSS receiver, the incoming signal is correlated with a local replica of signal code, obtaining the time difference information. The time difference is then transformed into a range information by multiplying it by the speed of light in the vacuum. However, since the receiver clock is not synchronized with the transmitters clock, this measure suffers of time bias, which is considered as an additional unknown in the navigation solution. Finally, the user position is determined on an Earth centred reference system with a process denoted trilateration, by exploiting the range information computed by the receiver and the information contained in the SIS navigation message, such as satellite ephemeris [Kaplan et al., 2005].
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