Galileo clock failures
Ten atomic clocks have failed on Galileo navigation satellites, casting doubt on the date of the next launch.
ESA's Director-General stated at his annual briefing that the Agency has not decided whether to go ahead as planned with the Ariane 5 launch of 4 satellites in August. "We have to find some systematic root cause, or go on launching and say ‘OK, there might be some failures’. Should we not launch until we have solved the problem? We are right now in this discussion as to what to do.”
Five satellites are affected - 3 initial validation (IOV) and 2 operational (FOC). But, with each satellite carrying 4 clocks, redundancy has ensured that no satellite has fewer than 2 working time references, and all affected satellites remain operational.
Both types of clock are involved - 3 rubidium atomic frequency clocks and 7 more-precise passive hydrogen masers, although one of these has since been restarted. The Swiss firm Spectratime produces both types of clock.
ESA has stated that, while investigations continue, some refurbishment is required on the remaining rubidium and hydrogen maser clocks still to be launched.
There are 18 Galileo satellites in orbit:
- 11 usable
- 4 under commissioning (latest 4 launched)
- 2 under testing (in wrong orbits)
- 1 unavailable (permanent failure)
The 11 usable satellites are providing 'initial services', declared on 15 December. Full capability is planned by 2020 latest.
Picture of passive hydrogen maser from ESA.
Details from the links below . .