KALMAN FILTER DESIGN FOR JWST SPACECRAFT ATTITUDE DETERMINATION SYSTEM

摘要

This paper describes an 8-state Extended Kalman Filter (EKF) design for the James Webb Space Telescope (JWST) fine pointing mode attitude determination. Due to the stringent pointing requirements imposed on JWST, the single star measurement from the fine guidance sensor (FGS) in the telescope is incorporated into the typical two star tracker (ST) based spacecraft attitude determination system. However, the tower type structure of the large telescope is subject to thermal deformation. Therefore, the FGS alignment has to be calibrated during the flight. A simple covariance analysis is used to assess the effectiveness of this 8-state EKF. The result indicates this design can achieve accuracy better than 0.5 arc-sec (3σ) in the FGS cross axes. Selective analysis results are also presented in this paper.