Galileo is a satellite-based global navigation system created by the European Union through the European Space Agency (ESA) and operated by the European Union Agency for the Space Programme (EUSPA). With its headquarters in Prague in Czechia, the system has two ground operations centers in Oberpfaffenhofen/Germany, and in Fucino/Italy, where the former is primarily responsible for the control of the satellites and the latter is mostly responsible for providing the navigation data.
Named after the Italian astronomer Galileo Galilei, one of the aims of the system is to provide an independent high-precision positioning system so that the European authorities do not have to rely on the United States GPS or the Russian GLONASS systems, which could be disabled or degraded by their operators at any time. The use of basic (lower-precision) Galileo services is free and open to everyone. Previously only available to government-authorized users, higher-precision service has also been available for free since January 2023. Galileo also provides global search and rescue (SAR) functionality as part of the Medium-Earth Orbit Search and Rescue (MEOSAR) system.
Galileo Historical Development
In 2008, the three main contributors of the European Space Agency (ESA) (Germany, France and Italy) presented their different concept proposals for Galileo. These were compared and unified by a joint team of engineers from these countries. The first stage of the Galileo programme was agreed upon officially on 26 May 2003 by the European Union (EU) and the ESA. Between 2003 and 2006, countries such as China, Israel, India were also accepted as partners in the programme; but in mid-2006, the public–private partnership dissolved due to security concerns and financial issues. Consequently, the European Commission decided to nationalize Galileo as an EU programme. The project began offering limited services in 2016.
While the development of the first generation of the Galileo programme was mainly led by Italy and Germany, France has taken a more prominent role in the development of the Galileo Second Generation (G2G).
Unlike the more military-focused approaches of the systems of the United States (GPS), Russia (GLONASS) and China (BeiDou), Galileo is primarily intended for civilian use, and hence it does not impose any particular accuracy limit for non-military applications. But still Galileo could also be subject to shut down for military purposes in extreme circumstances such as in the event of a potential armed conflict.
Constellation and Frequency Utilization
The original constellation plan of the Galileo system was to have 30 in-orbit satellites (24 in full service and the additional ones as spares) orbiting at the MEO level at an altitude of 23,222 km having orbital periods of 14 hours and 5 minutes (so that every 17 revolutions done in 10 sidereal days, which means that a satellite passes over the same location). 3 orbital planes were utilized for the constellation, where 8 operational satellites and at least 2 active spares per orbital plane were planned. As of December 2025, Galileo system consists of 23 active and healthy satellites, and it is planned to achieve 26 and 32 satellites by the end of 2027 and after 2027, respectively.
As in all other GNSS systems, each Galileo satellite broadcasts radio signals from its on-board atomic clocks, providing its location, status, and precise time. These signals travel through space at the speed of light. Whenever a relevant device receives these radio signals, it determines the exact time of arrival and uses this information to calculate its distance from each satellite in view. Once a Galileo receiver knows its distance from at least four satellites, it can use geometry to determine its location on Earth in three dimensions.
Similar to other systems, the signals must be modulated onto a carrier wave to be sent from the satellite to the receiver. The frequency utilization of the system is as follows:
- E1 (1575.42 MHz = 10.23 MHz × 154),
- E5 (1191.795 MHz = 10.23 MHz × 116.5),
- E5a (1176.45 MHz = 10.23 MHz × 115),
- E5b (1207.14 MHz = 10.23 MHz × 118), and
- E6 (1278.75 MHz = 10.23 MHz × 125)
Note that all the utilized frequency values are determined as multiples of 10.23 MHz (in fact integer multiples of 1.023 MHz), which are also encountered in the US GPS system. The choice of such frequencies for the GPS system is historically due to the usage of Rubidium-based oscillators, which have been quite stable and cost-effective during the design phase of the GPS system in 1970s. The aforementioned standardized frequency relationships ensure that the system’s different signals are coherently tied together, all originating from a highly stable oscillator (like an atomic clock) running at the core 10.23 MHz rate within the relevant satellites. This design decision additionally eases the design of dual-capability (GPS and/or Galileo) receivers.
Conclusion
With its open services, Galileo has been an essential element of the European Union as regards applications requiring accurate position and time information. Though not as widely adopted as its US counterpart GPS, Galileo technology is increasingly incorporated into various commercial and scientific applications. It constitutes a backbone and serves as a vital safeguard for the European ecosystem, in case the other GNSS systems are out of service and/or unavailable due to any reason.
