New optimal approach to space-stable inertial navigation system

Inertial navigation is typically performed using an instrumented platform stabilized in a local-level configuration. However, the local-level frame of reference must be maintained by gyro torquing, inducing attitude errors which may be intolerable for the more sensitive inertial devices currently being developed. Therefore, it is necessary to adopt space-stable mechanization to avoid the gyro torquing. In this paper, a space-stable inertial navigation system is developed, where an inertial, rather than geographic, reference is used for navigation calculations. The error model for the space-stable inertial navigation system is derived. Then an unscented Kalman filter is proposed to solve the nonlinear state estimation problem of the error model. Finally, the result shows that a good performance is achieved with a tractable computational load.