Despite early battlefield successes, US-made weapons augmented by Global Positioning System (GPS) satellites for position updates in Ukraine are now susceptible to Russian electronic warfare (EW) jamming, reported the New York Times (NYT) and the Washington Post, but it is unclear whether other factors are involved.
The weapons affected may include the 155mm Excalibur artillery projectiles, Ground Launched Small Diameter Bomb (GLSDB), Joint Direct Attack Munition (JDAM) and weapons rounds used with the High Mobility Artillery Rocket System (HIMARS), among others, depending on how they are employed by the weapons operators.
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An unnamed source reportedly familiar with the classified report told the NYT that in the worst-case scenario, only one in 19 Excalibur rounds was hitting its target, where the report said the cost per successful strike skyrocketed from $300,000 to $1.9 million between January and August 2023.
“The Excalibur technology in existing versions has lost its potential,” read the report, as cited by the Washington Post.
Two unnamed Ukrainian artillery commanders told NYT that Ukraine has stopped employing these weapons as a result.
The NYT article, published on Saturday, said the reports were first revealed by the Washington Post on Friday, while the second report was “described but not shown” to an NYT reporter.
Faltering performance of Excalibur
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NYT said the report’s claims that Russian EW has rendered US Excalibur rounds ineffective were allegedly substantiated by sources in the Ukrainian military.
Excalibur projectiles have the target’s GPS coordinates entered pre-launch. Like other GPS-aided precision-guided weapons, they are guided to the target using an inertial navigation system (INS), and the GPS modules provide external references of their physical coordinates as weapon location updates throughout the time of flight to the target.
However, Russian EW could theoretically disrupt their ability to receive accurate satellite data by either noise jamming (drowning out the signals) or spoofing (providing false satellite time-stamp signals), causing the weapons, using false data in its own positional calculations, to drift off course accordingly.
A Kyiv Post analysis published in April 2023, when Excalibur saw extended use in Ukraine, posited that the GPS-aided rounds could reach up to 50 kilometers and within 4 meters of their target.
NYT said the reports on Excalibur were compiled based on nearly 3,000 shells fired using US-provided M777 howitzers on the Kherson, Kharkiv and Bakhmut fronts between December 2022 and August 2023.
It said the hit rate dropped from 55 percent in January 2023 to 6 percent in August, when Ukraine’s counteroffensive was in full swing – however, the Washington Post article also pointed out that the data in later months were incomplete, as cautioned by the report.
“We have some problems with accuracy,” an artillery commander in the 45th Brigade operating in the Donetsk region told NYT regarding the use of Excalibur, adding that his unit has stopped using them since early 2023 due to their ineffectiveness.
The Washington Post added that Ukraine had stopped using Excalibur before the US suspended its deliveries partly due to the time-consuming calculation and programming, instead favoring standard howitzer rounds.
The article did not note that this calculation is critical for the weapons to be used in assuring targeting success, and that Ukrainian reluctance to follow these procedural steps to expedite battlefield employment could contribute considerably to miss distances.
The publication did add that the performance of guided munitions supplied by other nations – some not aided by GPS – also became less effective, though it’s not clear why.
Effects on other GPS-guided munitions
According to the classified reports, Russian jamming also affected other GPS-aided munitions, including air-launched JDAMs and ground-launched HIMARS.
JDAMs, which are essentially glide kits attached to dumb bombs, zero in on their targets using onboard INS aided by GPS signals similar to Excalibur, where the GPS signals provide coordinate references.
“The navigation system is initialized by transfer alignment from the aircraft that provides position and velocity vectors from the aircraft systems,” read the US Air Force’s site, adding that coordinates are “loaded into the aircraft before takeoff, manually altered by the aircrew before weapon release, or automatically entered through target designation with onboard aircraft sensors.”
When GPS-aided weapons are employed by Western aircraft the munition is provided with enhanced GPS capability used only in specific combat conditions. It is not clear whether MiG-29s or Su-27s have the ability to hand off this encrypted enhancement, something that would be easily solved if employed from an F-16 or other NATO fighter, bomber or attack aircraft.
The Washington Post, citing the report, said that soon after the JDAMs were used in Ukraine in February 2023, the hit rate dropped within weeks after its “nonresistance” to jamming was discovered and exploited, where they missed the targets by 65 feet (19 meters) to about three-quarters of a mile (close to one kilometer).
However, according to the US Air Force, the weapon should be able to hit within a 30-meter radius even without GPS assistance in ideal circumstances.
“In its most accurate mode, the JDAM system will provide a weapon circular error probable of 5 meters or less during free flight when GPS data is available. If GPS data is denied, the JDAM will achieve a 30-meter [circular error probable] CEP or less for free flight times up to 100 seconds with a GPS quality handoff from the aircraft,” it said.
As for HIMARS, claims of its ineffectiveness caused by Russian jamming were also substantiated by military sources without providing information of what is meant by ineffective.
While they were effective in striking ammunition depots and command points behind enemy lines in 2022, Russian jamming has impeded their effectiveness since 2023, where an unnamed battalion commander told the Washington Post how he witnessed the HIMARS missing the Russian target one shot after another through a reconnaissance drone.
There was no information provided on how target coordinates and elevations were collected by reconnaissance drones that may be using other coordinate systems (like older UTMs often used by ground troops rather than the WGS84 coordinate system used by GPS), nor how the height above mean sea level was determined, if used at all.
A senior Ukrainian military official confirmed the claims that HIMARS became less effective due to the lack of GPS signals caused by Russian EW systems.
“Everything ended: the Russians deployed electronic warfare, disabled satellite signals, and HIMARS became completely ineffective,” he told the Washington Post.
While Kyiv still considered HIMARS to be an effective weapon overall, following improvements from the West, another unnamed Ukrainian official told the publication that Russian jamming still affects its performance.
“When it’s, for example, a pontoon bridge… but there’s a 10-meter deviation, it ends up in the water,” he said.
Given that a typical pontoon bridge is 2.5 to 3 meters wide, such overall ineffectiveness of any long-range attack with any weapon is usually high. This normally means weaponeers would allocate many munitions attacking from very critical angles or the use of laser or visually updated weapons to further refine accuracy.
How do Russian EW systems affect the accuracy of GPS-aided munitions?
Assuming the findings of the classified reports are accurate – bearing in mind that it’s not a standard military practice to divulge weapon performance in war time – there are multiple ways that Russian EW can interfere with GPS-aided weaponry.
Most GPS-aided weaponry relies on the initial and target coordinates and calculates the path and trajectory using satellite provided time-stamp signals and then using the receiver’s (the weapon’s) own 3-D triangulation calculations accordingly, meaning that any deviation in the process can throw the weapon off course.
It’s possible that in addition to GPS interference, the initial or target coordinates were inaccurate to begin with, which needs to include not only latitude and longitude but also target elevation above mean sea level (MSL), rendering the guidance less effective. In the case of artillery and HIMARS strikes, it’s common for Ukrainian troops to spot the target through drones or reconnaissance units, where a room of error can theoretically exist due to Russian EW systems in operation.
It is also not known how Ukrainian drones derive target elevation without finding that information using a laser or radar altimeter and comparing that to the drone’s altitude (which may or may not be accounted for or known) to calculate the MSL of the object in question. Target elevation in weapons employment is critical to minimize weapons impact errors and is nearly as important as accurate latitude and longitude coordinates.
Since certain weapons rely on GPS time-stamps and onboard 3-D positional calculations based on this in mid-flight to adjust their courses – as in the case of some drones – Russian troops can theoretically “spoof” the GPS modules by feeding it false GPS satellite time-stamps, which would also throw the weapons off course – a tactic Ukraine has used against Russian drones to some effect.
Another bit of information not provided is what level of inaccuracy was introduced and what was required to be considered a hit. This depends on the type of target and the type of weapon in use along with a myriad of factors not mentioned, or perhaps even considered, by either the Ukrainian sources or the NYT and Washington Post articles.
While it’s a known fact that Russia has developed advanced EW capabilities, how exactly it managed to throw GPS-aided munitions off course remains unclear based on the NYT and Washington Post articles.
Addressing the issue
The Washington Post said the Excalibur were no longer supplied to Ukraine, while some, such as the JDAMs, continued to receive updates from the US to help them resist Russian jamming.
It said Kyiv and Washington, alongside manufacturers, are working on solutions to counter Moscow’s EW capability, though an unnamed Ukrainian official told the Washington Post in interviews that bureaucracies have prevented both from developing solutions in a timely manner.
Unnamed US defense officials told the publication that Washington anticipated the issues and is working with Kyiv to “evolve and make sure that Ukraine has the capabilities they need to be effective,” which mirrored Kyiv’s defense ministry statement that it “regularly receives recommendations to improve the equipment.”
Regarding JDAMs, it’s reported that Ukraine has continued to use them after the manufacturer provided improved systems last May to make them less prone to GPS jamming.
A recent Kyiv Post article also reported that the US planned to provide Ukraine with JDAM equipped with add-on radar seekers to target Russian GPS jammers specifically, turning the weapon affected by Moscow’s EW systems against the threat itself.
HIMARS is now equipped with “additional equipment to ensure good geolocation,” a senior official told the Washington Post, while Kyiv has reportedly asked Washington to provide them with the M26 unguided cluster munitions, which can remain effective over a large area despite GPS jamming.
Other Western-supplied weapons, such as the UK-supplied Storm Shadow missiles, are equipped with other forms of navigation alongside the GPS systems, including an internal terrain matching system, which made them less susceptible to Russian GPS jamming.
Another solution is to target Russia’s EW equipment, which Kyiv has been able to destroy with some success, particularly in occupied Crimea where Ukrainian troops were able to strike the command posts and other high-value targets after destroying radars and EW systems.
Overall, experts and unnamed officials agreed that there is a race to develop countermeasures between Kyiv and Moscow, and effective measures from either side can soon become obsolete.
“The life cycle of a radio in Ukraine is only about three months before it needs to be reprogrammed or swapped out as the Russians optimize their electronic warfare against it,” said Daniel Patt, a senior fellow at the Hudson Institute, as quoted by the NYT.
“The peak efficiency of a new weapon system is only about two weeks before countermeasures emerge.”
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