Why the Galileo System Failed

Embarrassing: In July 2019, the European navigation system Galileo had failed for 11 days. Now details about the cause have become known.

Nothing about the cause was announced at that time, except that there was a problem with the base stations. The failure caused hardly any problems, as almost all navigation devices can receive signals from several satellite navigation systems. So the operation with GPS and GLONASS simply continues.

Now, however, further details have become known on how the failure occurred. An important component of satellite navigation systems is the time signal, because the receivers calculate their own location by determining the signal propagation times. To do this, a time synchronization signal is sent from the ground to the satellites. In the case of Galileo, it comes from one of the system's two atomic clocks. One is located in Oberpfaffenhofen near Munich, another in Fucino, Italy. There was a technical problem with the clock in Fucino, which is why it was temporarily deactivated. What the technicians in Italy did not know was that the clock in Oberpfaffenhofen was in maintenance mode at the same time and could not send a time signal for the satellites either. For some time the satellites could still work, but after a day they stopped broadcasting. Galileo's emergency service was not affected as it transmits on a different frequency. The problem was additionally fired because the coordination of the restoration of the service took a long time.