Jamming GPS does not blind a guided weapon. Convincing it is somewhere else does.

In short: satellite navigation signals arrive so weak that a modest transmitter can drown them out, and that is the easy attack. The harder one is spoofing, where a false signal feeds a wrong position that the guidance computer accepts as true. Modern weapons answer with inertial navigation, multi-constellation receivers and antennas that null the jammer.

The intuition most people carry is that jamming turns a smart weapon into a dumb one. That is only half right, and the wrong half is the dangerous one.

קראו גם: The missile does not pick the target. The system behind it does. · Laser air defense: the weapon that changes the cost of every intercept · Most drones are stopped without a single shot fired

Why the signal is so easy to bury

A GPS satellite transmits from roughly 20,000 kilometres away. By the time the signal reaches a receiver on the ground it sits below the ambient noise floor, and the receiver recovers it only by correlating a known code. Any transmitter nearby that pushes noise into the same band raises the floor and breaks the correlation. Commercial jammers sold as privacy devices for delivery drivers already do this across a few hundred metres.

Scale that to a military emitter and the denial zone reaches tens of kilometres. Civil aviation has been reporting exactly this effect around active conflict areas for several years, with crews losing satellite position while flying near contested borders.

Jamming versus spoofing

A weapon that loses satellite lock knows it lost it. A weapon that is spoofed does not know anything is wrong, which is why spoofing is treated as the more serious problem even though it is far harder to execute.

What guided weapons fall back on

Inertial measurement units carry the weapon through the gap. Accelerometers and gyroscopes track motion from a known starting point, and the position estimate drifts slowly rather than vanishing. Over a short flight the drift stays inside the warhead's effective radius. Over a long cruise it does not, which is why the two systems are coupled rather than stacked.

• Multi-constellation receivers that also read Galileo, GLONASS and BeiDou, forcing a jammer to cover more bands
• Controlled reception pattern antennas that steer a null toward the jammer's direction
• Terrain or scene matching in the terminal phase, comparing what the seeker sees to stored imagery
• Encrypted military signal codes that a commercial spoofer cannot reproduce
• Sanity checks that reject a position jump inconsistent with the inertial solution

The defensive side of the same coin

Navigation attack is also a defensive tool, and it is the quiet reason that most drones are stopped without a shot fired. A small quadcopter relying on civil GPS is far easier to push off course than a guided munition, and the interception costs nothing per attempt.

The decision of when to jam belongs to the same layer that decides when to fire, because the system behind the missile picks the target. Jamming broadly also degrades your own navigation and your own drones. The same discipline applies here as in deciding what a radar chooses to ignore.

Assume satellite navigation will be unavailable when it matters, and judge any system by how well it flies without it.

Source: Inertial navigation system, Wikipedia