Ch 5. Galileo

José Ángel Ávila Rodríguez, Jörg Hahn, Miguel Manteiga Bautista, and Eric Chatre

European Space Agency, and European Commission

Chapter Overview:

The increasing role of satellite navigation moved the European Space Agency (ESA) and the European Commission (EC) back in 2003 to develop the Galileo system, the European contribution to global satellite navigation.

Galileo has been designed to provide independent satellite-based positioning worldwide and increased accuracy, availability‚ and continuity. Galileo is not only compatible with all other navigation systems such as GPS, GLONASS‚ and BeiDou, but it is also interoperable with them.

Galileo shares with other GNSSs the physical principle of using radio signals to determine the user’s position based on passive RF trilateration. Accurate time plays a fundamental role, and high-precision clocks are flown on board Galileo satellites. Galileo carries the most accurate atomic clock ever flown in space and based on passive hydrogen maser clock technology.

Galileo’s signal plan is in-line with ongoing modernization of other navigation systems. This ultimately results in a clear benefit for the users in terms of improved navigation performance and robustness, enhancing accuracy and resilience against common modes of failure.

This chapter describes the Galileo system. Section 5.1 outlines the history of the Galileo Programme, describing the historical key elements in Section 5.1.1, while Section 5.1.2 addresses its signal evolution. Section 5.2 explains the management structure of the Galileo programme, reviewing the roles and relationships of all organizations. Section 5.3 describes the Galileo Geodetic and Time Reference System, and Section 5.4 depicts all Galileo services including performance targets. Sections 5.5, 5.6, and 5.7 provide an overview with key characteristics of the Galileo's space segment, ground segment, and signal plan, respectively. Section 5.8 summarizes Galileo's ionosphere model, while Section 5.9 summarizes Galileo's navigation performance. Finally, Section 5.10 provides a vision of where Galileo could evolve in the years to come.

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Figure 5.9 First Galileo launch with Ariane 5 carrying four satellites on 17 November 2017. Source: © ESA – S. Corvaja.

Figure 5.16 Galileo frequency plan, signals‚ and components.