An Optimal Tightly-coupled Stellar/inertial Integrated Navigation Method for Daytime Application

In the stellar/inertial system, the accumulated error of inertial navigation system (INS) can be restrained by the star tracker, which is capable of providing 3-axis attitude information by using at least 2 stars in the field of view (FOV). Unfortunately, there are usually not enough bright stars in the FOV for attitude determination in the daytime. To overcome this limitation, a new tightly-coupled stellar-inertial integration method based on the observation of predicted star centroid error is developed in this paper. The mathematical model of the proposed method is derived in detail, and its feasibility is investigated by numerical simulations. The simulation results show that the tightly-coupled method can get better navigation performance than the loosely-coupled method, and is particularly suitable for the stellar/inertial system with small FOV star tracker for daytime applications.