The United States’ confidence in the Iraq war is largely based on high-tech military equipment. Guided bombs such as JDAM can theoretically carry out precise “surgical” strikes against hostile parties. The Iraqis used low-cost signal jammers in an attempt to jam the mythical Global Positioning System (GPS) weapons guidance signals. signal jammer
This kind of GPS jammer is only the size of a mobile phone and can be purchased in the market for a few hundred dollars. The Iraqis regard it as a magic weapon to “defeat foreign artillery” – it is said that it can interfere with the GPS signal, thereby allowing the Americans to accurately The weapon was “hitting crookedly.” It is said that the US military has found and destroyed 6 such jammers in Iraq.
The US military’s “Global Positioning Satellite System” is a signal network composed of 27 satellites. It can not only position and control weapons, but also provide navigation for troops and aircraft accurate to meters. If the GPS signal can be interfered with for a long time, it will cause the entire logistics system of the US military to malfunction.
Before the war began, U.S. military experts warned that the Iraqis’ GPS jammers might disable U.S. guided bombs. Douglas Lowero, the person in charge of the GPS system program in the United States, believes that this is nonsense. There is no instrument on the market that can effectively interfere with GPS signals.
How powerful is this gadget?
A Russian company makes such a cheap GPS jammer. Theoretically, this jammer can interfere with satellite signals within a radius of 200 kilometers. The signal sent by U.S. navigation satellites to the GPS receiving antenna is very weak, and its strength is only about one billionth of the signal received by a general TV antenna. Therefore, satellite navigation systems commonly used in automobile transportation, navigation and adventure travel are very susceptible to interference from such GPS jammers. However, navigation equipment used for military purposes is relatively “robust” and less susceptible to interference.
The “C/A” code of the GPS system is used for civil purposes, and its positioning accuracy can reach about 5 meters. The military uses the “P” code, which has a positioning accuracy of up to one meter.
Not only is the military’s “P” code more precise, it’s also encrypted and therefore less susceptible to interference. Douglas Lowero believes that military GPS codes are thousands of times more resistant to interference than civilian codes. He said that GPS jammers are only effective within a radius of a few kilometers. At most, they can only interfere with GPS-guided weapons within this range, and it is impossible to make guided weapons stray.
In addition to satellite positioning systems, the U.S. military’s precision weapons are also equipped with another navigation mechanism-the Inert Navigation System (TNS). The TNS system will not be interfered by external signals. Its working principle is to use the inertia of the high-speed rotating gyro system for positioning. Before the precision bomb is launched, the TNS system is input with a set of parameters that define its starting position; after the bomb is launched, the gyro system interprets each trajectory change relative to the starting position as a steady-state disturbance, thereby performing a new position calculation. describe.
The positioning error of a GPS-guided bomb is about 3.5 meters, while the positioning error of TNS is about 20 meters. If used to attack military installations, this positioning error of TNS can be ignored. However, if it is used to attack military targets in residential areas, the possible consequences of this error cannot be underestimated.
