WASHINGTON — The makers of precision-guided munitions no longer take for granted that simple GPS-guidance systems will always work on their own. Jammers and spoofing equipment threaten to populate future battlefields; manufacturers have taken notice and answered the threat.
Put simply, a jammer broadcasts noise such that GPS receivers in their vicinity — which rely on weak signals from distant satellites — are overwhelmed and lose the actual GPS signal. If a precision-guided bomb, a minute away from hitting its target, loses the lock, the results could be disastrous.
Fifteen years ago, jammers were considered expensive equipment most common to governments or nation states. But now low-cost, low-powered jammers are everywhere, riding the wave of cheap, reliable consumer electronics like Wi-Fi routers and smartphones. Although military GPS systems are more resilient than their commercial cousins, there is no 100 percent guarantee, particularly against a high-powered jammer.
A $25 Chinese-made jammer, found online, can block the GPS signal around a car, while a two- or three-watt jammer the size of a cigarette pack, available for a couple hundred dollars, could envelop several city blocks, said Joe Rolli, who heads Exelis' GPS jammer detection program, Signal Sentry.
"Anybody who wants it has got it," said James Hasik, a senior fellow at the Atlantic Council and author of "The Precision Revolution: GPS and the Future of Aerial Warfare." "To be frank, you and I could build a GPS jammer in the basement quickly."
In April, Deputy Defense Secretary Bob Work told a crowd at the US Army War College in Carlisle, Pennsylvania, that guided munitions and advanced weaponry, like GPS jammers, will be features of future ground warfare.
Russian-backed separatists in Ukraine and their state sponsors have "very definitely" been using advanced electronic warfare equipment, he said, and the Defense Department has been working to discern how effective these were in jamming command-and-control networks and GPS frequencies.
"And these technologies are proliferating as widely as conventional guided munitions," Work said. "So in the future, US Army and US Marine forces, and our allies that fight with us, are going to have to fight on a battlefield that is swept by precision-guided munitions, but also one that is swept by persistent and effective cyber and electronic warfare attacks."
Douglas Loverro, deputy assistant defense secretary for space policy, told lawmakers in a March 25 congressional hearing that the Defense Department had increased its space defense budget by $5 billion, with a portion dedicated to anti-jam capabilities on satellites and in user equipment.
On the precision-guided munition side, the US Air Force Research Laboratory at Eglin Air Force Base, Florida, is studying a kind of seeker that directs bombs to detect and destroy GPS jammers, called home-on-GPS jam, or HOG-J.
Last year, the lab awarded Scientific Applications & Research Associates of Cypress, California, a $9.8 million contract to integrate the seeker into the JDAM and Small Diameter Bomb Increment I (SDB-I) weapons and demonstrate it in flight tests. The work, at White Sands Missile Range, New Mexico, is expected to be completed by late 2016.
Alan Shaffer, deputy assistant defense secretary for research and engineering, said at a 2014 congressional hearing that, "HOG-J has had some preliminary successful tests and could be ready to enter the inventory in two to three years."
It's unclear precisely how vulnerable the JDAM is to GPS jamming. Flint, the JDAM program manager, declined to discuss a report in the Jerusalem Post which said North Korea's jamming of GPS signals in South Korea in 2011 affected its JDAM arsenal, but he said the company is taking the threat of GPS-denied environments seriously enough to modify its weapons.
"I can't comment on specific incidents, but we do consider GPS jamming to be a very viable scenario and a potential threat to the accuracy and performance to the weapons we have achieved," he said.
"GPS jamming has really evolved over the last five or six years, and the laser really gives you a great capability to go GPS independent," Flint said.
In search of GPS-level accuracy in areas without a signal, Boeing is developing a navigation system that can recognize a stationary target from a picture. The pilot or another operator could send a picture of, say a group of buildings, and designate which building the bomb must hit.
"We're using the revolution in electronics to counter some of these things, so it's definitely a spy-versus-spy scenario," Flint said.
Rockwell Collins has a four-element antenna, the Integrated GPS Anti-Jam System (IGAS), used in the JDAM, Simon said. Twenty years ago, antennas were single-patterned and captured an analog signal, but Rockwell Collins and Raytheon have produced controlled reception pattern antennas with as many as seven elements, controlled by digital antenna electronics.
Commercial GPS typically operates on the L1 frequency, while the military operates on L2 as well, with the ability to encrypt on both. That ability, even without embedded anti-jam capability, protects military GPS devices. Products like IGAS are meant to provide even more protection.
To combat battlefield obscurants, SDB II, which Raytheon is building for the Air Force, uses a three-mode seeker: a millimeter-wave radar to detect and track targets through weather, an imaging infrared for enhanced target discrimination, and a semi-active laser that enables the weapon to track an airborne laser designator or one on the ground.
Raytheon announced in May that the Air Force is moving toward low-rate initial production, with plans to put it on the F-35, F/A-18E/F and F-16 aircraft. Initial planning has also started for integration on the Super Hornet.
The 2016 president's budget requests $184.8 million for 100 Raytheon-made tactical Tomahawk block IV cruise missiles. Among other improvements, it will be able to perform in-flight retargeting, loiter over the battlefield and feature improved anti-jam GPS.
Textron Systems plans to incorporate its semi-active laser into its 50- or 70-pound G-CLAW, named for the Clean Area Warhead (CLAW) originally developed for the US Air Force but never used. The company's 12-pound Fury has GPS-aided inertial navigation and a semi-active laser seeker for terminal guidance.
Intended for manned and unmanned platforms, the G-CLAW in September completed a live-fire demonstration recently at the US Army's Yuma Proving Ground in Arizona. From 10,000 feet, Textron dropped the G-CLAW from a Cessna Caravan aircraft equipped with a US Special Operations Command common launch tube dispenser.