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Satellite-navigation systems & jamming
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- Infrastructurally speaking: The term “critical infrastructure” bring to mind solidly earthbound images: road and rail networks, water and sewage pipes, electricity grids, the internet, and so on. Such stuff is so crucial, it is taken for granted. One piece of infrastructure which has become critical over recent decades, is the various constellations of satellites, the most familiar of which is probably America’s Global Positioning System (GPS), that orbit about 20,000 km above Earth, broadcasting to the world precisely where they are and exactly what time it is.
- Why was it made: The original purpose of the GPS and its European (Galileo), Russian (GLONASS) and Chinese (BeiDou) counterparts was to enable suitably programmed receivers on or near the ground to calculate their whereabouts to within a few centimetres, by comparing signals from several satellites.
- In this role they have become ubiquitous, running everything from the navigation systems of planes, ships and automobiles, both military and civilian, to guiding the application of water and fertiliser in precision agriculture. But global-navigation satellite systems (GNSS), to give their collective name, now do much more than that.
- By acting as clocks that broadcast the time accurate to within a few dozen nanoseconds, they are crucial to jobs ranging from co-ordinating electricity grids and mobile-phone networks to time-stamping financial transactions and regulating the flow of information in and out of data centres.
- Weak spot: The GNSS networks have a weak spot. The satellites’ transmitters broadcast with the wattage of a refrigerator lightbulb. Their signals are so vanishingly faint that they arrive “beneath the noise floor” of ambient electromagnetic radiation. This makes them vulnerable to interference, both accidental and deliberate. The more uses which GNSS constellations are put to, the more this matters. So those engineers are looking at ways to harden and back up the whole idea.
- Jamming: It sometimes happens accidentally. In January 21, it emerged that GPS failures which had been plaguing aircraft near Wilmington International Airport, in North Carolina, were caused by wireless equipment at an unnamed nearby utility. GNSS networks are also vulnerable to “natural” jamming by the arrival from the sun of coronal-mass ejections of electrically charged particles. Most often jamming is deliberate too!
- Local problems can be caused by personal privacy jammers (PPJs). These are devices—widely available for sale even though generally illegal to use—which scramble GPS signals to stop vehicles being tracked by nosy employers or suspicious spouses. Thieves also find them useful. They are, for example, involved in 85% of vehicle thefts in Mexico.
- Further up the commercially available scale are wide-area jammers. These devices, which are about the size of suitcases, do have legitimate quasi-civilian uses, such as protecting potential targets, public or private, from attack by GNSS-guided drones or missiles. But misused, whether deliberately or accidentally, they can disrupt GNSS across an area the size of a city.
- In this context it is notable that the northern Black Sea, where many Russian bigwigs, supposedly including the country’s president, Vladimir Putin, have country estates, is a hot-spot for GNSS outages that affect shipping in the area.
- At the high end of GNSS disruptors are military systems, which can muddle signals for hundreds of kilometres around. Collateral effects from these are a growing problem. In 2019 the number of recorded incidents reached 3,564—nearly 22 times more than had been noted two years previously. Most hotspots were near war zones. South Korea’s capital, Seoul, for instance, often experiences GNSS outages for which the only plausible explanation is jamming from North Korea, the border with which is only about 40km away.
- Alternates needed: In America this search has been reinforced by the National Defence Authorisation Act, which became law on January 1st. This obliges the country’s armed forces to generate “resilient and survivable” positioning and timing capabilities by 2023. One approach to doing so is to upgrade the satellites themselves. America’s air force, for example, has begun launching a generation of new “GPS III” satellites built by Lockheed Martin, a defence giant. GPS III offers somewhat stronger signals than its predecessor. But its main advantage is an encryption system, the details of which remain classified. Satelles, a firm in Virginia, is using Iridium, a constellation of 66 satellites orbiting at an altitude of just 800km, to re-broadcast encrypted time data sent from a network of high-precision clocks on the ground, together with data about the satellites’ locations (thus mimicking the functions of a GNSS network), to clients including telecommunication firms, data centres, stock exchanges and banks.
- Summary: Some people are trying to revive the idea of land-based navigation beacons similar to the Loran (long-range navigation) towers used by the American and British navies during the second world war. Many countries are now constructing enhanced “eLoran” networks. These include China, Iran, Russia, Saudi Arabia and South Korea.
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