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Bougard, Bruno
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Bougard, Bruno
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- PublicationRestrictedAssessing the GNSS scintillation climate over Brazil under increasing solar activity(2013)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ;We study ionospheric scintillation on GNSS signals at equatorial latitudes to draw a climatological picture of the low latitude ionosphere in the Brazilian sector during the ascending phase of the upcoming 2013 solar maximum. Such data have been acquired during the early stage of the CIGALA project (http://cigala. galileoic.org/), funded by the European Commission under the 7th Framework Program and the outcome of this work is part of the scientific achievements of the project itself. The considered network is based on the novel PolaRxS receivers, developed and deployed specifically to comply with the aims of the FP7 project. The PolaRxS is able to monitor ionospheric scintillation for all operational and upcoming GNSS constellations (GPS, GLONASS, Compass, GALILEO) and corresponding frequencies in the L-band. The ionosphere over the Brazilian territory, being close to the southern crest of the Equatorial Ionospheric Anomaly (EIA), is heavily affected by intense scintillation conditions. The sector under investigation is also very peculiar with respect to other low latitude regions, because of its proximity to the South Atlantic Magnetic Anomaly (SAMA). The application of the Ground Based Scintillation Climatology (GBSC) technique, for the first time simultaneously on GPS and GLONASS data and on both L1 and L2 frequencies, highlights the joint effect of the EIA and of the SAMA in producing the irregularities leading to scintillation.203 3 - PublicationOpen AccessTackling ionospheric scintillation threat to GNSS in Latin America(2011-10)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;Veettil Sreeja, V.; Institute of Engineering Surveying and Space Geodesy, University of Nottingham, Nottingham, NG7 2RD, UK ;Aquino, M.; Institute of Engineering Surveying and Space Geodesy, University of Nottingham, Nottingham, NG7 2RD, UK ;Forte, B.; Institute of Engineering Surveying and Space Geodesy, University of Nottingham, Nottingham, NG7 2RD, UK ;Elmas, Z.; Institute of Engineering Surveying and Space Geodesy, University of Nottingham, Nottingham, NG7 2RD, UK ;Hancock, C.; Institute of Engineering Surveying and Space Geodesy, University of Nottingham, Nottingham, NG7 2RD, UK ;De Franceschi, G.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Alfonsi, Lu.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Spogli, L.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Romano, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Bougard, B.; Septentrio N. V., Greenhill Campus, Interleuvenlaan 15G, 3001 Leuven, Belgium ;Galera Monico, J. F.; Faculdade de Ciencias e Tecnologia, Departamento de Cartografia, Universidade Estadual Paulista Julio de Mesquita Filho, Rua Roberto Simonsen, 305, Presidente Prudente, SP, Brazil ;Wernik, A. W.; Space Research Center, Polish Academy of Sciences, ul. Bartycka18a, 00-716 Warsaw, Poland ;Sleewaegen, J. M.; Septentrio N. V., Greenhill Campus, Interleuvenlaan 15G, 3001 Leuven, Belgium ;Canto´, A.; Pildo Consulting, SL, Parc Tecnologic de Barcelona Nord Office A216-A220, Marie Curie 8-14, 08042 Barcelona, Spain ;Da Silva, E. F.; Consultgel Consultoria em Geomatica Ltda, Rua Jose Tognoli, 238, Presidente Prudente, SP 19060-370, Brazil; ; ; ; ; ; ; ; ; ; ; ; ; ; Scintillations are rapid fluctuations in the phase and amplitude of transionospheric radio signals which are caused by small-scale plasma density irregularities in the ionosphere. In the case of the Global Navigation Satellite System (GNSS) receivers, scintillation can cause cycle slips, degrade the positioning accuracy and, when severe enough, can even lead to a complete loss of signal lock. Thus, the required levels of availability, accuracy, integrity and reliability for the GNSS applications may not be met during scintillation occurrence; this poses a major threat to a large number of modern-day GNSS-based applications. The whole of Latin America, Brazil in particular, is located in one of the regions most affected by scintillations. These effects will be exacerbated during solar maxima, the next predicted for 2013. This paper presents initial results from a research work aimed to tackle ionospheric scintillation effects for GNSS users in Latin America. This research is a part of the CIGALA (Concept for Ionospheric Scintillation Mitigation for Professional GNSS in Latin America) project, co-funded by the EC Seventh Framework Program and supervised by the GNSS Supervisory Authority (GSA), which aims to develop and test ionospheric scintillation countermeasures to be implemented in multi-frequency, multi-constellation GNSS receivers.403 160 - PublicationOpen AccessL-band scintillations and calibrated total electron content gradients over Brazil during the last solar maximum(2015)
; ; ; ; ; ; ; ; ; ; ; ; ; ; ; ;; ; ;This work presents a contribution to the understanding of the ionospheric triggering of L-band scintillation in the region over São Paulo state in Brazil, under high solar activity. In particular, a climatological analysis of Global Navigation Satellite Systems (GNSS) data acquired in 2012 is presented to highlight the relationship between intensity and variability of the total electron content (TEC) gradients and the occurrence of ionospheric scintillation. The analysis is based on the GNSS data acquired by a dense distribution of receivers and exploits the integration of a dedicated TEC calibration technique into the Ground Based Scintillation Climatology (GBSC), previously developed at the Istituto Nazionale di Geofisica e Vulcanologia. Such integration enables representing the local ionospheric features through climatological maps of calibrated TEC and TEC gradients and of amplitude scintillation occurrence. The disentanglement of the contribution to the TEC variations due to zonal and meridional gradients conveys insight into the relation between the scintillation occurrence and the morphology of the TEC variability. The importance of the information provided by the TEC gradients variability and the role of the meridional TEC gradients in driving scintillation are critically described.421 120 - PublicationOpen AccessInvestigation of low latitude scintillations in Brazil within the cigala project(2011-09)
; ; ; ; ; ; ;Romano, V.; Istituto Nazionale di Geofisica e Vulcanologia, Sezione Roma2, Roma, Italia ;Bougard, B.; Septentrio N. V., Leuven, Belgium ;Aquino, M.; University of Nottingham, Nottingham, United Kingdom ;Galera Monico, J. F.; Univ Estadual Paulista, Faculdade de Ciências e Tecnologia, Pres. Prudente, Brazil ;Willems, T.; Septentrio N. V., Leuven, Belgium ;Solé, M.; Pildo Consulting S.L., Barcelona, Spain; ; ; ; ; Ionospheric scintillations are fluctuations in the phase and amplitude of the signals from GNSS satellites occurring when they cross regions of electron density irregularities in the ionosphere. Such disturbances can cause serious degradation on GNSS system performance, including integrity, accuracy and availability. The two indices internationally adopted to characterize ionospheric scintillations are: the amplitude scintillation index, S4, which is the standard deviation of the received power normalized by its mean value, and the phase scintillation index, σΦ, which is the standard deviation of the de-trended carrier phase. At low latitudes scintillations occur very frequently and can be intense. This is because the low latitudes show a characteristic feature of the plasma density, known as the equatorial anomaly, EA, for which a plasma density enhancement is produced and seen as crests on either side of the magnetic equator. It is a region in which the electron density is considerably high and inhomogeneous, producing ionospheric irregularities causing scintillations. The upcoming solar maximum, which is expected to reach its peak around May 2013, occurs at a time when our reliance on high-precision GNSS (such as GPS, GLONASS and the forthcoming GALILEO) has reached unprecedented proportions. Understanding and monitoring of scintillations are essential, so that warnings and forecast information can be made available to GNSS end users, either for global system or local augmentation network administrators in order to guarantee the necessary levels of accuracy, integrity and availability of high precision and/or safety-of-life applications. Especially when facing severe geospatial perturbations, receiver-level mitigations are also needed to minimize adverse effects on satellite signals tracking availability and accuracy. In this context, the challenge of the CIGALA (Concept for Ionospheric scintillation mitiGAtion for professional GNSS in Latin America) project, co-funded by the European GNSS Agency (GSA) through the European 7th Framework Program, is to understand the causes of ionospheric disturbances and model their effects in order to develop novel counter-measure techniques to be implemented in professional multi-frequency GNSS receivers. This paper describes the scientific advancements made within the project to understand and characterize ionospheric scintillation in Brazil by means of historical and new datasets.391 375