A Fast Calibration Method of the Star Sensor Installation Error Based on Observability Analysis for the Tightly Coupled SINS/CNS-Integrated Navigation System

The strap-down inertial navigation system/celestial navigation system (SINS/CNS)-integrated system can be divided into the loosely coupled integrated mode and the tightly coupled integrated mode. Because the loosely coupled integrated mode requires the star sensor to observe at least three stars at the same time to obtain the attitude matrix, the tightly coupled integrated mode, which can still work with only one star, is more practical in reality, especially for the aircraft that need to work in the daytime. The star sensor is a vital part of the CNS, while its installation error impacts the navigation accuracy seriously in both the modes. Therefore, the star sensor installation error of the SINS/CNS-integrated navigation system must be corrected. The installation error calibration has been settled for the loosely coupled SINS/CNS-integrated navigation system when the attitude matrix is available. However, it is still a problem for the tightly coupled mode. This paper proposes a fast calibration method of the star sensor installation error for the tightly coupled SINS/CNS-integrated navigation system based on maneuvers and observability analysis. Simulations indicate that the proposed method is feasible and effective when only one star is visible at a time. The mean position error of the tightly coupled SINS/CNS-integrated navigation decreases by about 63.23% after compensation for the star sensor installation error.