Abstract:

An approach to polar stellar-inertial navigation utilizing a grid coordinate system is presented. The conventional inertial navigation mechanizations is not suited for transpolar flights due to the convergence of the longitude meridians at the poles which cause a mathematical singularity in the navigation equations. The method proposed here utilizes a grid reference frame and the grid meridians are everywhere parallel to the Greenwich meridian, based on which, the grid mechanization equations and error equations are derived. Since the meridians do not converge at the poles, the grid mechanization is well suited for polar navigation. The requirement for military aircraft inertial navigation systems with all-earth, completely self-contained, high precision and long-flight capability can be achieved through aiding with star-tracker. The difference between the inertial platform measured and computed lines of sight vectors to a star provides an ideal observation for the stellar-inertial Kalman filter to estimate or correct inertial navigation errors. The simulation results show that the position error propagation is less than 400 m for an 8 h flight and the proposed scheme is effective in polar navigation.