Navstar Global Positioning System

The global positioning system (GPS) is truly unique when compared to other Department of Defense space assets.1 Although GPS was originally procured to aid in navigation, it has become a universal system used by both the civilian world and the military. GPS has become so integrated into our everyday lives that the Department of Homeland Security has declared it a part of the United States’ critical infrastructure. Used by cell phones, computers, and cars, GPS can be found everywhere. This chapter will discuss the GPS missions; segments; limitations and vulnerabilities; tactics, techniques, and procedures; and modernization efforts.2