The recent outage of GALILEO has clearly demonstrated that any Global Navigation Satellite System (GNSS) can - from one second to the other - simply fail. Luckily, the US NAVSTAR GPS has shown a strong performance and good resilience so far. Nevertheless, we should urgently develop a "backup plan" for GNSS, as more and more procedures require high integrity and accuracy navigation solutions and thus DME, IRS and "RADAR vectors" will not be good enough anymore...
This topic is known as Alternative Positioning Navigation and Timing (APNT). I recently published a scientific paper about this and you are invited to read it... (click on the paper below):
