ESA reported first problems with functioning their navigation system. Issues spotted already in 2017 are first serious problems since announcing start of Galileo Initial Services by European Commission on 15 December 2016.
According to ESA, which coordinates and operates Galileo, at least four from eighteen satellites from present constellation of Galileo are affected with problem. Defect affects onboard atomic clocks - each satellite is equipped with four atomic clocks. Ten clocks were reported as not working , one managed to restart and at the present moment is operating normally. Problem appeared in the half of January 2017.
Devices affected with problem are both Hydrogen Masers (6 units) and Rubidium clocks (3 units) installed inside two different types of satellites. In-Orbit Validation (IOV) satellites by Airbus and Thales Alenia and first generation of regular navigational satellites by OHB Systems reported same issues. It was spotted that no more than two clocks failed in each satellite, what makes all satellites remain with one line of redundancy and are still able to operate.
Highly accurate timing devices like atomic clocks (hydrogen maser clocks from Galileo satellites are accurate to one billionth of a second per day),are one of the key elements of every satellite navigation system. Signal generated by clocks is transmitted to users on the ground and helps in establishing correct position.
Swiss company which was provided atomic clocks for Galileo spacecrafts, SpectraTime, already started to cooperate with ESA to evaluate potential reasons for this problem.
ESA already decided to postpone launch of next series of Galileo satellites from August 2017 to November 2017. Mission covers delivering to orbit Galileo FM19 - FM22 satellites manufactured by OHB Systems and planned to be launched from Guiana Space Center on the to pof Arianespace Ariane 5 rocket.