Analysis and Compensation of Sun Direction Error on Solar Disk Velocity Difference

Solar disk velocity difference is an emerging celestial navigation measurement acquired through four spectrometers positioned on the four corners of the quadrangular pyramid. The alignment of the pyramid’s axis with the direction from the sun to the spacecraft is crucial. However, the sun sensor measurement error inevitably leads to the sun direction error, which both significantly affect navigation accuracy. To address this issue, this article proposes an augmented state sun direction/solar disk velocity difference integrated navigation method. By analyzing the impact of the sun direction error on sun direction and solar disk velocity difference measurements, the errors of the solar elevation and azimuth angle are extended to the state vector. The navigation method establishes state and measurement models that consider these errors. Simulation results show that the position error and velocity error of the proposed method are reduced by 97.51% and 96.91% compared with those of the integrated navigation with the sun direction error, respectively. The result demonstrates that the proposed method effectively mitigates the impact of sun direction error on navigation performance. In addition, the proposed method can maintain a satisfactory error suppression effect under different sun direction error values.