A Performance Model of an Integrated Navigation Solution Using Satellite Observations from Star Trackers

This paper defines the major system components of a navigation system that integrates a star tracker observing satellites on a star background with an inertial measurement unit (IMU). By modeling the components and their respective errors their contribution to the navigation position error is evaluated to reflect the key performing parameters. The scenario of interest models the navigation performance of a moving vehicle that integrated an IMU with a star tracker. By imaging a satellite on a star background, the star tracker measures two angles. Those angles, when associated with a time, describe a 3-D line of sight vector on which the observer must lie. This research determines the component error sources to such measurements and the expected performance of a navigation system that integrates these measurements with an inertial system. The results show the expected navigation error vary according to star tracker quality, satellite ephemeris error, IMU quality, and observed satellite selection algorithm. The method described in this work improves on previous celestial navigation techniques by tightly integrating the measured line of sight angles with an IMU while using the physical specifications of the sensors to define the measurement accuracy.