An On-Orbit Initial Alignment Method for Reusable Spacecraft with INS Star Sensor and GPS

Abstract

Many countries have been focusing on developing reusable spacecraft. For on-orbit alignment of reusable spacecraft, attitude determination is a vital problem. When developing a navigation system with an Inertial navigation system (INS) and star tracker, the misalignment between the two systems must be estimated so that measurements from both systems can be converted to a common reference frame. An innovative on-orbit alignment method for reusable spacecraft is proposed in this paper. This method utilizes Extended Kalman Filter (EKF) to estimate navigation errors and IMU biases, as well as the misalignment angle between INS and star tracker. The simulation results show that with good estimation of the misalignment angle between INS and star tracker, the positioning and orientation accuracy of INS/Star tracker integrated navigation system is greatly improved, so the method is effective and suitable for reusable space craft.