Where am I, how do I get there, and what time is it?
These are three questions that must be answered to accomplish many military and civil tasks. Denying this information to an enemy and preventing an enemy from denying friendly forces this information is the essence of navigation warfare (NAVWAR).
Before the development of Global navigation satellite systems (GNSS) like the U.S.’s Global Positioning System (GPS), Europe’s Galileo, and Russia’s GLONASS:
Self-location depended on inertial navigation systems which lost accuracy as a function of time since leaving a known, surveyed location
Navigation depended on calculation of the direction and distance from a current location to another location
Timing depended on clocks
All of these were based on surveyed locations and celestial navigation – very time consuming.
Now they are based on location and timing information from Earth satellites, and thus require communication to and from those satellites and communication among friendly assets.
This communication must be near instantaneous to support military and many civil applications.
There are hundreds of thousands of military systems which depend on navigation satellite systems to move, attack and communicate.
It is essential that such systems maintain their capabilities even when satellite navigation related signals are degraded or unavailable.
Civil applications include financial transactions, air traffic control, and rail traffic safety (such as the activation of crossing barriers, weather monitoring, earthquake detection, and coordinating and routing first responders.
Interfering with the passing of this information or degrading its accuracy is the essence of offensive NAVWAR and preventing these activities is the essence of defensive NAVWAR.
Related to this, it is essential that military forces know when their critical satellite signals are being spoofed or jammed so that the dependability of GNSS dependent activities can be assessed and defensive measures initiated.
Also, critical military systems must be able to withstand GNSS outages caused by rigorous jamming and spoofing.
Enemy forces are continuously deploying more advanced jamming and spoofing technologies worldwide, jeopardizing the security and reliability of PNT data that feeds into GNSS receivers, downstream networks and subsystems.
Offensive NAVWAR measures include the jamming and spoofing of enemy communications to and from satellites and between friendly locations.
Defensive NAVWAR measures include jamming resistant antennas, communications electronic protection (including special modulations), and alternate techniques for determining PNT data during interruption of GNSS operation.