Satellite-navigation systems such as GPS are at risk of jamming

THE PHRASE “critical infrastructure” conjures up solidly earthbound images: road and rail networks, water and sewage pipes, electricity grids, the internet, and so on. Such stuff is so wound into the warp and weft of life that it is simultaneously both essential and taken for granted. One piece of infrastructure which has become critical over recent decades, though, is anything but earthbound. This is the various constellations of satellites, the most familiar of which is probably America’s Global Positioning System (GPS), that orbit about 20,000km above Earth, broadcasting to the world precisely where they are and exactly what time it is.