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How Europe is Challenging GPS | European GPS System (Galileo Satellites) Explained

Galileo is the European Global Navigation Satellite System (GNSS), often seen as a counterpart to GPS. The program started in 2007 with its initial planning phase. The Second Phase was sattelite testing and the thrid Phase Installation, with an in Orbit Validation where the sattelite was developed by Astrium and launched by a Soyouz rocket. Currently, Galileo is in its fourth phase, where the system is fully operational under the management of OHB, with satellites being launched by Ariane 5 and 6 rockets.
In general the system consists out of 24 Sattelites in 3 Orbital planes at an altitude of 23200km. Each orbital plane contains 8 satellites, spaced 40 degrees apart. Each satellite has an orbital period of 14 hours, providing a 90% probability of having at least four satellites visible from any point on Earth's surface.
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Gallileo offers different services for different applications, here you can see the different frequency bands of the services. The open service is avaible for use by anyone with approprate mass market equipment without charge. Additionally, a High Accuracy Service, offering precision up to 1 cm, is also free of charge. The Public Regulated Service (PRS) is a more robust option, with enhancements from ground stations, but access is restricted to governmental bodies. Lastly there is the search rescue service, this service makes it possible to send feedback to the sattelite, to locate and area where help is needed, for example for millitary applications.
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The Layout of a Gallleo sattelite is modular. Thorugh this production and assembly prcocesses can run mouch more effectively.  The mass of a sattelite is 700kg, it uses 1,5 kw of power for operation and its Size is 2,7 times 1,2 times 1,1 meters while The solarpanel area of  the sattelite is 14,8 square meters. The Liftetime for one sattelite is expected to be longer than 12 years, after that the sattelite has to be replaced by a new one.
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The Components for the sattelite which you can see here are developed and manufactured by many different suppliers. The Components can therefore be qualified in parallel. The most important Component of the gallieo sattelite is the clock monitoring unit, an atomic clock is essential for the position determinantion. Antother really important component is the low power antenna, which uses frequencies between 1100 and 1600 MHz. Due to the low power of 50watts there is only noise at the reveiver.
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A quiet unique feature of the gallileo sattelite, is its production process. It is manufactured in serial production because of the large number of satteltites required. This is really untypical in the space industry , often sattelites are one time builds and no serial produciton line is needed. The method used is the so called island approach which has the goal to output 1 sattelite every 6 weeks, while the runtime through the production line Is 11,5 months , the modular assembly of the sattelite makes this possible in the first place.
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The next generation of gallileo sattelites is already planned, and expect to be avaible in 2025. These new satellites will feature electric propulsion systems, allowing for multiple satellites to be inserted into orbit in a single launch.

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