• Red faces in Brussels. European Galileo global satellite navigation system forced to fall back on GPS
• System down for more than four days - and counting
• Explanations are brief and vague
• Most likely cause seems to be global reference time clocks getting out of sync

Galileo, Europe's very own global navigation satellite constellation, has been offline for  more than four days now and counting. Explanations as to the cause of the outage are brief and vague. All that is being said is that system is down due to a “technical incident related to its ground infrastructure". That ground infrastructure is notoriously complex.

Whatever the root cause, all servers, devices and other links to the system remain inoperative because they cannot receive positional or timing data from the satellites. And so, with considerable embarrassment and political squirming, the EU is currently having to rely on good old GPS (the venerable US 'Global Positioning System'), the one that Galileo is supposed to supersede in terms of accuracy and robustness.

Galileo is an initiative of, is owned by and is being paid for by, the European Union under the auspices of the the European GNSS Agency (GSA) and the European Space Agency. The first indications that something was seriously wrong first became apparent last Thursday when the GSA posted an alarm on its website stating that Galileo's services "have degraded and may not be available nor meet the minimum performance levels." 

The alert was upgraded on Saturday with the announcement that 24 of Galileo's 26 satellite constellation are "not usable" while the remaining two are classified as being in "testing phase" and thus, also, as much use as a chocolate teapot. The statement added that users (various governmental agencies and private companies) determined to try to use Galileo would do "at the users' own risk." Later in the day that was changed to the stark warning, "Galileo systems are not to be used."

After seventeen years of development, many technical glitches, delays and false starts, Galileo was eventually launched in 2016 and, although it is still in what is called it's "roll-out pilot-phase", now provides both paid-for commercial services (increasingly used by private companies) and free-at-point-of-use services for government agencies, universities and academia, including disaster recovery and other global navigation purposes.

Global positioning systems now vital to the global economy

In a somewhat degraded spin-off civilian version, GPS was first made available as a commercial service by the US Air Force as far back in 1978. From then on GPS quickly established itself as a vital part of the global economy and is now fundamental to a wide range services in hugely important industry sectors including telecoms, IT, energy and oil and international finance.

Speculation about the cause of the outage is rife on the Internet with explanations ranging from interference by extra-terrestrial beings through to interference by state-sponsored hackers. Also we should not forget that when the Galileo system was first mooted and all the way through its design and implementation phases the US threatened, in extremis, to shoot down the constellation in the event of a serious inter-regional or global political crisis, not least because Galileo was, from the outset, designed to be tougher, more accurate and harder to jam than GPS. In the end after some pressure and horse-trading Galileo's frequencies were changed to alternatives that could be more easily degraded or jammed and thereafter things went quiet, but we live in strange and unsettling times.

However, a more prosaic fault explanation is likely and rumours have it that the cause of the outage is a serious problem with Galileo's Precise Timing Facility (PTF) which is sited in on the ground in Italy. The PTF generates and manages the exact reference time by which the entire Galileo constellation is calibrated. If the GNSS clocks go out of sync and the satellites do not get correct updated timing data, positioning accuracy will quickly degrade to the point where the entire constellation will be compromised and go down.

As this article is being written, Galileo is still offline and the GSA continues to stand by its earlier assertion that "Experts are working to restore the situation as soon as possible." It adds," An Anomaly Review Board has been immediately set up to analyse the exact root cause and to implement recovery actions."

It's all a bit of a mess, and if Galileo was as fully commercially functional as it is supposed to be by now, the impact would be extremely severe. As it is, the GSA has egg on its face and EU technocrats are puce with embarrassment.​