US, allies rush to refit their big guns with GPS protections

THE HAGUE, Netherlands — The war in Ukraine has jump-started a scramble to fortify artillery systems against GPS jamming and spoofing, with a technology previously used primarily on airborne platforms playing a key role.

The rush to inject new defenses into cannon and rocket artillery systems, in particular, represents the latest round of a cat-and-mouse game in the electromagnetic spectrum. Invisible to the human eye, its mastery determines not only whether projectiles find their intended targets; but in some cases whether weapons will function at all.

The American-made HIMARS rocket launchers, for example, touted as a game changer after they were delivered to Ukraine, quickly faced problems that stemmed from GPS jamming, senior U.S. officials have admitted.

The Washington Post was the first to report the story last year, based on a confidential report on the effectiveness of weapons in combat. The verdict was damning: After the initial success and hype, HIMARS was now deemed “completely ineffective” at the hands of Russian jamming by the Ukrainians using them along the front line.

Multiple rocket launcher systems such as HIMARS rely on clear GPS data to operate effectively. For one, the vehicle must be able to detect precisely where it located in order to determine its relative position to the target. It also must be able to determine the location of GPS satellites in the sky above it, as this is vital information that is uploaded – along with other guidance data – to the missile right before launch in the form of what is referred to as an “almanac.” Once the missile leaves the launcher, it is typically on its own.

Some self-propelled howitzers, including French CAESAR and Swedish Archer types, are now also banking on GPS in their fire control systems.

Air-to-ground equipment

Buried in the U.S. Army budget request for fiscal year 2025, there are several mentions of upgrades to the GPS system of the service’s fleet of mobile missile launchers, amounting to a total of $75 million. The Army has bought a total of 376 anti-jamming kits for its HIMARS rocket launchers over the past two years, the documents show. A further 284 for both HIMARS and also the fleet of M270A1 vehicles are slated to be bought between 2025 and 2029.

The kit in question, the Digital GPS Anti-Jam Receiver, or DIGAR, is sold by BAE Systems and was originally intended for air warfare, where it has already found wide application – including being retrofitted onto American F-16 and F-15 fighter jets. Recently, it has also been slated for integration into Eurofighter Typhoons.

The more modern F-35 fighter jet goes with a competing solution by contractor Lockheed Martin, which also makes the plane.

“Integrating on a land vehicle does not require any more effort than going from one platform to another,” a BAE Systems spokesperson told Defense News. The main difference, according to the company, lies in the terrestrial environmental conditions in the form of dust, debris and rocket residue.

The roughly laptop-sized silver box has become a preferred way of countering electronic warfare targeting GPS signals, which even under the best of conditions are remarkably faint owing to the tens of thousands of kilometers of distance between the satellites and the surface of the Earth.

According to one industry insider, who spoke on condition of anonymity to discuss the technology, testing by the U.S. Air Force had shown that “if a user was still being jammed even after fitting DIGAR, then the enemy transmitter would be so close you could engage it with a rifle.”

Other nations also are focusing on the threat of GPS interference to their heavy weaponry. In Denmark, the procurement of new, Israeli-made MLRS systems to replace those that were sent to Ukraine ended up mired in controversy after a report by the country’s public broadcaster alleged they were vulnerable to GPS attacks – a claim that was refuted by the manufacturer.

The U.K., for its part, has bought over 1,000 of Raytheon’s Landshield anti-jamming systems, which are roughly the size of a hockey puck. And Israel has been developing anti-jamming technologies, including for undisclosed foreign customers, using the new military M-Code GPS standard, which was designed to be resistant to interference.

“All the internationals are going to get DIGAR,” the industry insider said, referring to foreign users of American-made HIMARS launchers. In the case of European users, some had already started shipping their launchers to the U.S. to be taken apart, upgraded and then reassembled. All the newly manufactured HIMARS will get DIGAR right from the assembly line, the insider said.

While Lockheed has publicly announced that it will upgrade M270 launchers – the bigger, tracked version of the weapon – for “global partners,” there is to date no matching statement regarding HIMARS.