Navigation Using Doppler Shift from LEO Constellations and INS Data

Absolute navigation using the downlink communication signals of massive LEO constellations augmented by data from an Inertial Navigation System (INS) is considered. Lack of atomic clocks on-board LEO satellites requires the use of Doppler shift as a navigation observable. Furthermore, footprint limits of downlink signals' beams necessitates the use of a tightly-coupled INS/radio-navigation filter in order to compensate for the fact that it is not possible to measure carrier Doppler shift simultaneously from 8 or more satellites. The navigation solution error is shown for a situation which demonstrates the feasibility of combining measurements from LEO constellations and INS data to enable GNSS-like navigation capabilities. Finally, an investigation is performed to study how navigation solution error is affected by IMU quality, signal availability, and downlink spot beam steering protocol.