The European Space Agency (ESA) has celebrated the Galileo satellite navigation system meeting civil aviation standards governing flight phases from take-off to landing and explained how the feat was done.

The requirements around Safety-of-Life operations are laid down by the International Civil Aviation Organization (ICAO) and govern the use of systems where a malfunction would have catastrophic consequences.

Galileo was not designed to comply with ICAO's rules. After all, Europe already had the European Geostationary Navigation Overlay Service (EGNOS), which supplements the US Global Positioning System (GPS). The system permits accuracy to within 1.5 meters and since 2011 was declared compliant for Safety-of-Life operations.

Considering Galileo is the European Commission's bid to free itself of dependence on GPS, using it for civil aviation had a certain inevitability. Augmentation by EGNOS would be required for take-off and landing.

The question is, how robust is Galileo? According to ESA, only six events in the history of Galileo "exceeded the standards set by ICAO, and none of them were affecting more than a single satellite at a time."

Impressive until one considers the 2019 event when the network suffered a "service degradation" and served up inaccurate positioning information over a period of several days.

ESA fails to mention this incident in its latest wording about Galileo meeting avation standards, however, we imagine that any airline betting an aircraft full of passengers on the system would need reassurance that similar failures would not happen again.

To get the coveted Safety-of-Life endorsement, engineers had to tweak the ground segment to mitigate the effects of the "very few" potential malfunctions. The satellites themselves were either already in orbit or on their way. Oddly, ESA should have commented on why it was that the requirement for the rigorous standards set by the ICAO only came up when it was too late to update the design of Galileo.

The fix ended up being all in the software. "In the end, not a single infrastructure or hardware element was touched," said Stefan Wallner, head of the Galileo Signal-in-Space Engineering Unit. "We improved the monitoring and notification capabilities of Galileo purely by retuning the software in the ground segment."

The improvements received the stamp of approval from the ICAO in March 2023, meaning that Galileo (alongside GPS) can support non-critical phases of flight. Upcoming augmentation with EGNOS is still needed for operations such as landing.

However, why wasn't the Galileo system designed with this in mind in the first place? The first launch of the US GPS system was in 1978. Galileo's first launch happened in 2011.

The second generation of the Galileo program is now under development and will go hand-in-hand with EGNOS v3, which is capable of augmenting Galileo as well as GPS. ®

https://www.theregister.com//2024/01/30/esa_galileo_aviation/