Which option correctly describes the GPS control system components?

• A. The satellites' on-board clocks and timing system
• B. A set of user receivers in all aircraft
• C. A network of ground-based monitoring and control stations with 5 monitoring stations, 3 ground antennas, and 1 master station
• D. A single master station with no ground antennas

Answer: (C)

The key idea is that the GPS control system is the ground-based part that maintains and updates the satellites’ data. The control segment consists of a network of monitor stations scattered around the world that track satellites and collect ranging data, a master control station that processes all that data to generate precise ephemeris and clock corrections, and ground antennas used to communicate those corrections to the satellites. This is separate from the satellites’ on-board clocks (which are part of the space segment) and from the user receivers (which are the user segment). A single master station with no ground antennas wouldn’t be able to communicate with the satellites or maintain the navigation data, so it wouldn’t function as the GPS control system. The description with multiple monitoring stations, ground antennas, and a master station matches how the GPS control system is actually organized.