GNSS technology to support air navigation

• Grant number: 19/06000-9
• Support Opportunities: Scholarships in Brazil - Scientific Initiation
• Start date: April 01, 2019
• End date: March 31, 2020
• Field of knowledge: Physical Sciences and Mathematics - Geosciences - Geodesy
• Agreement: CNPq - INCTs
• Principal Investigator: Joao Francisco Galera Monico
• Grantee: Gustavo Patara Onishi
• Host Institution: Faculdade de Ciências e Tecnologia (FCT). Universidade Estadual Paulista (UNESP). Campus de Presidente Prudente. Presidente Prudente , SP, Brazil
• Associated research grant: 17/50115-0 - GNSS technology for supporting air navigation, AP.PP

Abstract

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, especially the American Global Positioning System (GPS), 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 influences from ionospheric layer strongly, 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 Brazilian territory, especially on those regions 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. Investigations in this direction are of great importance due to judicious requirements on safety involved in aviation, because it involves risk to human lives. In this scenario, the proposal of creating this NIST (National Institute for Science and Technology, Instituto Nacional de Ciência e Tecnologia) has the objective of accomplishing a detailed analysis of errors decorrelation models owing to ionosphere (risk model), developed to be applied in the United States, which assure safety operation for precise landing systems, like GBAS. Such models require a feasibility analysis to be applied in Brazil, since ionospheric conditions are quite different from those ones where original models were developed. Additionally, adaptations and improvements will be proposed in this risk model to make it suitable for Brazilian reality in complying with ICAO accuracy, integrity, availability and continuity criteria. Investigations conducted in this NIST will also contribute to improve the combined use of GNSS and inertial systems. For the development of this project, a consistent and comprehensive data set from GNSS receivers over national territory is needed for the purpose of enabling analysis of Brazilian ionosphere specificities and, consequently, to make it possible to apply GNSS technologies for aerial navigation. For this reason, it is proposed an expansion in continuous monitoring networks available nowadays, which are constituted by GNSS receivers able to measure most important ionospheric activity parameters: Total Electron Content (TEC) and the ionospheric scintillation indices (S4 and P2). This exposed demand was proposed by the Department of Airspace Control (DECEA, Departamento de Controle do Espaço Aéreo) to provide Brazilian community a safe service for precise landing procedure. Data from this new network will be used to optimize GNSS receivers performance during incidences of ionospheric scintillations and, yet, to make it available to users an map, in real time, of errors caused by ionospheric delay and scintillation occurrence. Such maps are useful for several applications in geodesy, among them are precise agriculture and