A system used to determine a spacecraft's location, including its distance, velocity, and trajectory. NASA's deep-space network (DSN) uses such methods as Doppler, ranging, and antenna control. Distance is determined by uplinking data that the spacecraft echoes. Measuring the Doppler shift change of frequency on the vehicle's downlink carrier provides the velocity. Doppler and range measurements together provide the trajectory. Navigation files are used by the DSN to predict where to point their antennae.
Subjects: Astronomy and Astrophysics.