Abstract : The Global Positioning System (GPS) is a satellite-based radio navigation system that provides worldwide military and civil users satellite signals they can process to determine accurate position, velocity, and time. On May 8, 2000, the Under Secretary of Defense for Acquisition, Technology and Logistics (USD (AT&L)) approved entry into the initial modernization efforts for Navstar GPS. GPS III, an Acquisition Category 1D program, is the next generation Space Vehicle (SV) that will provide significant enhancements to complete the modernization of the constellation. GPS III complies with 10 United States Code (USC) 2281, ensuring the continued sustainment and operation of GPS for military and civilian purposes, and 42 USC 14712, continuing as an international standard available on a continuous worldwide basis free of direct user fees.