The GPS (Global Positioning System) has been fully functional for nearly two decades. GPS consists of 27 satellites positioned in a medium earth orbit. A satellite is considered to be in medium earth orbit when it is 35,000 kilometers above the Earths surface, roughly 22,000 miles. The first experimental satellite was launched in 1972. It was not until 1995, 23 years after the launch of the first experimental satellite, that GPS bore fruit as a fully function satellite tracking system. Even then the system was restricted to military and airline industry use.
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