Galileo Satellite Constellation: Overview
Galileo is a Medium Earth Orbit (MEO) satellite constellation consisting of 24 operational satellites, with an additional 6 in reserve. Positioned approximately 23,222 km above the Earth’s surface, they are inclined at an angle of 56° to the equator. The constellation is part of the European Union Global Navigation Satellite System (GNSS).
Background and Launch
Commissioned by the European Space Agency (ESA), the Galileo constellation was launched beginning in 2016. This initiative was established to ensure Europe had its own independent navigation system, while also being interoperable with other major systems like the US’s GPS and Russia’s GLONASS. One of the primary design objectives of Galileo was to provide enhanced satellite coverage. With its unique inclination angle, the system offers improved coverage in polar latitudes, areas where GPS traditionally exhibits weaker coverage.
Service and Coverage
Upon completion of its testing phase, Galileo is designed to offer consistent coverage over at least 90% of the Earth’s surface, ensuring that at least four satellites are visible from any given location at any time.  
In January 2023, the Galileo system introduced its High Accuracy Service (HAS) which achieves horizontal accuracy down to 20cm and vertical to 40cm, and is the first such system be freely offered to the public.