Russia’s bombardment of Ukraine with Iranian-designed Shahed drones is unrelenting, with 45 launched on the night of 10-11 Feb and another 14 last night. Over 3,700 Shahed attacks been recorded by December 21 and questions are raised about the Ukraine supply of air defense missiles. Now Ukraine has a new drone shield which does not rely on ammunition: a nationwide electronic warfare system called Pokrova with confuses drone navigation systems.
Valerii Zaluzhnyi, then Commander-in-Chief of the Armed Forces of Ukraine, revealed the existence of the system last November in a paper laying out his plans to break out the current military impasse.
“…the capabilities to counter high-precision enemy weapons (guided missiles, UAVs) are increasing due to the deployment of a nationwide ‘Pokrova’ electronic warfare system with the possibility of replacing the satellite radio navigation field (‘spoofing’), suppression of satellite radio navigation. along the entire line of contact and in most of the territory of Ukraine,” Zaluzhnyi wrote.
Pokrova is the Ukrainian name for the Feast Of Protection of the Mother of God, which celebrates an occasion in the 10th century when an apparition of the Virgin Mary is said to have spread her veil over a church in Constantinople during a siege, causing the besiegers to withdraw. Its namesake similarly throws a protective veil over Ukraine.
Jamming overwhelms navigation systems (GPS and others such as the Russian GLONASS) with noise. Spoofing causes them to give an incorrect location by generating a fake signal, and most of the known examples come from Russia. Drivers close to the Kremlin find their satnav tells them that they are at the airport, and ships in the Black Sea may appear to be miles inland. Putin appears to be surrounded by a bubble of spoofing, likely as protection against drone attacks.
Ukraine has brought down Russian tactical drones with spoofing from short range before, but Pokrova works on a much larger scale. This is technically challenging. Dr Thomas Withington, an electronic warfare expert at U.K .defence thinktank RUSI, told Forbes that it will require a network of perfectly synchronized transmitters. Fortunately Ukraine already operates a similarly synchronized system controlling radar in their national air defence network so they are already familiar with this area.
Shahed drones are well protected against electronic warfare. The current version have the Russian military Kometa-M navigation unit, a digital antenna array allowing it to identify and exclude jamming signals. According to the makers drones with Kometa-M can still find their way when the jamming is tens of thousands of times more powerful than the satellite signal.
The Shahed also has a backup inertial navigation unit or INS. This works even when there is no satellite signal, but drifts rapidly over time. The backup system provides accurate navigation for perhaps one minute – long enough to hit a target protected by a local jammer, or fly through a band of jamming before it can recover a satellite signal.
This combination makes the Shahed difficult to counter with conventional electronic warfare. But Ukrainian engineers have had the opportunity to take apart several Shaheds and work out the vulnerabilities of their navigation system.
“Spoofing might be a way of outflanking counter-countermeasures like jam-resistant receivers,” says Withington.
Spoofing is much harder to detect than jamming. If the spoofing signal is relatively subtle – gradually moving further and further away from the real location – the drone will have no way of telling that it is being spoofed, but will end up some distance from the target.
“We already have the ability to counter this system [Kometa-M],” Ivan Pavlenko, the Chief of the Main Directorate of Electronic Warfare and Cyber Security of the Ukrainian General Staff, stated in September.
The Shahed-136, with its relatively small warhead of about 45 kg/ 100 pounds, needs to strike close to the target to have any effect. Pushing it half a mile away guarantees c complete miss – though it may still damage something.
Russia’s multi-million-dollar cruise and ballistic missiles have more advanced navigation systems which do not rely on satellite signals, but the bulk of Russia’s attacks now involve Shaheds which are vulnerable.
Spoofing In Action
Zaluzhnyi did not say when Pokrova had been activated, but there may be some clues that it is working.
On February 3rd, the Ukrainian Air Force’s official Telegram channel noted that 11 Shahed had been shot down the previous night, and “In addition, at least seven attack drones did not reach their targets and were lost locally.”
In addition, there have recently been instances where Shaheds have been captured intact and appear to have been brought down with electronic warfare rather than missile or gunfire.
It is impossible to tell how effective Pokrova system is, or just how its spoofs navigation signals. Attacks take place at night, and the jamming will likely only be activated in times and places where drone attacks are taking place. Ukraine does not reveal any details of where Shaheds hit, denying Russia any information how many are finding targets. Russian developers will attempt to detect or counter the spoofing — and the Ukrainians will modify their system to counter the countermeasures. In the mean time, just because a Shahed is not shot down does not mean it hits a target.