Workshop 2018
João Francisco Galera Monico - GNSS NavAer network for supporting Ionospheric Studies in Brazil - October 29, 2018 • 426 Views
INCT in Portuguese is the acronym for Instituto Nacional de Ciência e Tecnologia, that means National Institute of Science and Technology. This is one of the largest program of Science and Technology in Brazil. The last call was named INCT 16/2014. At that time, researcher from Unesp (São Paulo State University), INPE (National Institute for Space Research), ITA (Institute of Aeronautical Technology) and IAE (Institute of Aeronautics and Space) submitted the project named “GNSS technology for supporting air navigation”, whose short name is GNSS NavAer. This six-year project was approved and we are at the beginning of the second year. The main stream of the project is related with the problem of ionospheric irregularities, specially scintillation (IS) for air navigation at the Brazilian region. Considering that the use of satellite positioning systems (GNSS) for aerial navigation constitutes a worldwide tendency in present days and, in the future, it will be the main technology adopted for determination of airplanes positioning in all flight phases. The application of this kind of technology has numerous benefits such as considerably reduced need of ground equipment installation, optimization of aerial space with routes, and reduction in flight duration and its consequent fuel saving, to mention a few. In this context, it can be highlighted the GBAS (Ground- Based Augmentation System), which uses GNSS systems, transmitting the corrections to improve the accuracy in determining the aircrafts position aiming at guiding it for a precise landing. However, GPS signals, as well as those ones of any other satellite positioning system, suffer strong influences from ionospheric layer, with introduction of errors that might affect accuracy, integrity, availability and continuity requirements postulated by International Civil Aviation Organization (ICAO). The ionospheric layer presents distinct behaviors according to location (mainly with latitude variation), hour of the day, period of the year and solar activity cycle, which period is of eleven years. The ionosphere over the Brazilian territory, especially on the region of equatorial ionization anomaly occurrence, presents singular features in comparison with other parts of the planet, due to concentration of phenomena and anomalies occurring there, making satellite positioning systems performance worse when compared to regions such as United States and Europe, for instance. Thus, the application of technologies based on GNSS in aviation over Brazilian territory demands a deep evaluation of ionospheric effects. For example, in the United State GBAS system expects ionospheric gradient of the order of 450mm/km, for the worst case. In Brazil it can be very worse. Therefore, a better understanding of all factor affecting the ionosphere in Brazil has to be reached. For doing that,we are expanding the up to now deployed network for monitoring the ionosphere, such as CIGALA/CALIBRA/GNSS-SP network, together with improvements in the ISMR Query Tool developed for supporting search in the data base, which is very large. An integration with other networks is under development, which will share the same kind of receivers. Therefore, a more deeply understanding of the ionosphere will be feasible of being realized. Several studies have already been carried out in Brazil. For instance, Pereira (2018) computed a great number of ionospheric gradients for all available GNSS stations in Brazil since 2000. Vani (2018) developed a tool for prediction of Ionospheric amplitude scintillation, via the S4 parameters available in the data base, using neural network. Vani et al. (2018) developed a new algorithm to mitigate the Ionospheric scintillation effects in the PPP. Short details of the project and part of the results obtained so far will be presented.


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