An on-orbit calibration system for satellite attitude control

To ensure the long-term on-orbit working precision of attitude sensors, a new approach for the high-precision three-axis stabilized satellite with the typical inertial/stellar measurement mode is presented. This approach employs a real-time on-orbit calibration system to estimate the measurement error of gyro by star sensor. The calibration system is achieved by using a second-order nonlinear filter in a closed-loop satellite attitude control system. Considering the error sources during the attitude measurement, a model of gyros misalignment, scale factor error and drift is constructed to compensate the corresponding errors. Comparing with the attitude control system without on-orbit calibration, this approach provides more attitude measurement information for satellite attitude determination and correction. The computation quantity is small and response time is short. Simulation results indicate that the real-time on-orbit calibration system is extremely effective in improving the attitude pointing accuracy and stabilization.