Air systems 31 US Space Force

GPS satellites operated by the US Space Force, which continuously transmit signals containing time and location information

technology. And because it’s so widespread, it’s not at the forefront of people’s minds – when you have something that is reliable and is just in the background, we don’t always see it.” Elisabeth Braw, resident fellow at the American Enterprise Institute, calls this “the convenience trap”. As she sees it, society’s relationship with technology since the dawn of time has been in the service of greater and greater convenience. However, this comes with a cost – in the case of GPS, our reliance on the functionality it provides has resulted in some troubling vulnerabilities.

GPS is made up of three components – satellites, receivers and ground control stations. GPS satellite signals carry a time code kept by incredibly accurate atomic clocks, which are synchronised with each other and with counterparts on Earth. The clocks enable each of the 31 GPS satellites operated by the US Space Force to continuously broadcast a signal that includes the time and the satellite’s predicted position. GPS receivers – whether they are installed on ships or as part of a smartphone – work out their latitude, longitude and altitude by measuring the relative time delay of signals broadcast by a minimum of four satellites. Today, GPS – and other global navigation satellite systems (GNSSs), such as the EU’s Galileo constellation – is used for everything from pizza delivery and earthquake measurements to automated vehicles and missile and projectile guidance. Efforts have been made to keep military and civilian GNSS systems separate – Galileo, for example, has two signals. One is for general use, while the public regulated service (PRS) used by militaries and emergency services is designed to be more resistant to attack. However, the overlap of military and civilian systems has inevitably caused friction. And, as GPS and navigational satellite systems have become embedded in military operations, adversaries have become increasingly intent on tampering with them, Braw explains. “Yes, the military always – in every area – uses more secure technology than the rest of us. But no technology is ever completely secure,” she says.

Attack the signal

As the use of GPS for military operations has increased, so too has the development of anti-GPS technology. This typically takes two main forms – jamming and spoofing. Russia and its proxies have proven to be particularly adept and eager with jamming GPS signals, which has led to an increasing awareness of its vulnerabilities among the Nato member states.

GPS jamming operates by targeting the receivers, producing a radio frequency signal strong enough to drown out satellite transmissions. The user will immediately be able to detect such an attack, whether deliberate or accidental, as the information


the receiver is supposed to pick up will no longer be available. This can lead to serious disruption, as seen in 2016 when South Korea was subjected to a major campaign of GPS jamming from North Korea, which affected ship and aircraft navigation. One of the main threats with jamming, Stickings notes, is that the perpetrators “don’t have to be a space actor to be able to interfere with space systems – [jammers] are fairly easy to come by”. Jammers are so readily available that they’re sometimes used by London taxi drivers to avoid the rules on maximum driving hours or to prevent their employers from tracking them. In 2013, Newark Airport’s air traffic management operations were regularly affected by a man whose commute took him past the airport – he was also using a jammer to stop his employers from tracking him. GPS spoofing, on the other hand, is “more of a cyber capability,” Stickings says. Sometimes called ‘denial-of- service’ spoofing, it involves deliberately mimicking the form of transmissions from GPS satellites, thereby tricking the receiver into believing that it has been sent information as expected.

“The idea with that is, for example, for navigation purposes, you’re not where you think you are, because you’re receiving a signal that’s actually incorrect,” she adds. “Or a precision-guided munition might not go where it’s intended to go. This is obviously more difficult [than jamming], because you have to create a signal that’s not easy to distinguish as being fake.” Such an event occurred in June 2017 in the Black Sea, when more than 20 ships operating near the Russian port of Novorossiysk realised that their satellite navigational systems placed them 32km inland, at Gelendzhik Airport. While not confirmed, experts at the time believed this to be the first documented use of GPS misdirection. The danger this can present comes down to international borders and territorial waters. An aircraft patrolling the edges of a border could be spoofed into accidentally crossing over and becoming an intruder – this can be particularly dangerous in contested areas, where such an incursion could serve as the pretext to violence.

Star wars

While jamming and spoofing both involve interfering with the receiver, satellites themselves could also become vulnerable to attack. A number of nations now boast anti-satellite missile capabilities, but Stickings sees this serving as more of a deterrent than something that will receive widespread use. “Destroying a satellite kinetically creates a huge amount of debris, which is particularly a problem in low-Earth orbit,” she explains. “It’s not in anyone’s interest to increase debris – there’s a fairly fine balance in space at the moment between the major powers and other users. I think that sort of activity would not happen until much later on in a conflict – certainly not in terms of first or second-strike capability.”

Defence & Security Systems International /

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