Spacecraft navigation is to give the position vector and velocity vector of controlled spacecraft to determine the spacecraft orbit method and process. Its main tasks include: (1) to determine the position and speed of the spacecraft in orbit; (2) calculate the future spacecraft orbit and landing point, as well as the initial conditions required for maneuver.
According to whether the acquisition of navigation data depends on the support of ground equipment, spacecraft navigation can be divided into two categories: autonomous navigation and non-autonomous navigation. The common non-autonomous navigation methods include tracking and measurement of spacecraft by ground station and orbit determination and tracking and data relay satellite. Autonomous navigation is not dependent on the earth or other celestial man-made facilities orbit determination methods, such as astronomical navigation and inertial navigation. For example, America's GPS and Russia's GNSS use autonomous navigation.
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