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Navigation operations is the process of identifying a destination, finding the path to the destination and performing the necessary tasks to transport a vehicle to the destination along with the passengers which may be people or science instruments. Navigation operations are synonymous with exploration and it is performed by engineers and explorers or ordinary people when they get in their car, turn on the GPS and drive to the mall. The GPS navigation system requires a GPS receiver and a map. GPS alone does not navigate. Spacecraft navigation to the bodies in the solar system is a bit more complicated than driving to the mall. The closest analogy to planetary spacecraft navigation is the navigation performed on Eighteenth century and earlier sailing ships. The navigator knows his home port and has a vague idea of the location of his destination. Once the ship sails beyond the horizon, its location is not known very well. The major problem is determining time. In order to determine longitude, the navigator must know the time in his home port where 12:00 PM is high noon. If high noon occurs at 1:00 PM he knows he is about 700 miles West of his home port depending on his latitude that can be determined from the elevation of stars above the horizon. Magellan carried 18 hour glasses for his voyage around the world. In determining a route, he must have some knowledge of wind and ocean currents. For planetary navigation, the navigator knows his home port, namely the Earth. He has a vague idea of his destination. If his destination is a planet, he can go out at night and look up and see his destination. The problem of determining where the spacecraft is located and plotting a route is shared with sailors of antiquity. Determination of time with atomic clocks enable the navigator to determine range to the spacecraft and is the key to planetary orbit determination. The major advantage of planetary spacecraft navigators over sailors of antiquity is that they perform navigation in a comfortable flight operations facility and do not die if they make a mistake.