A new attitude determination approach using split field of view star camera

Due to the character of the original source materials and the nature of batch digitization, quality control issues may be present in this document. Please report any quality issues you encounter to digital@library.tamu.edu, referencing the URI of the item.Includes bibliographical references (leaves 116-119).Issued also on microfiche from Lange Micrographics.A novel split field of view star tracker is being developed for the EO-3 GIFTS mission (2004). The camera is designed to be autonomously self-calibrating, and capable of a rapid/reliable solution of the lost in space problem as well as recursive attitude estimation. An efficient Kalman filter algorithm for the spacecraft attitude estimation problem has been developed. This algorithm makes use of three axis gyros for the rate data and star line of sight vector measurements derived from the split field of view star camera to estimate the spacecraft attitude and the gyro bias. An accidental gyro failure (e.g. failure of four of the six rate gyros on the Earth Radiation Budget Satellite) or intentional omission of gyros (e.g. in Small Explorer (SAMPEX)) due to their high cost can necessitate "gyroless" attitude estimation. Two different sequential algorithms have been developed for the spacecraft body angular rates estimation in the absence of gyro rate data for a star camera mission. Star camera calibration plays an important role for the case of the spacecraft attitude estimation problem. Two efficient Kalman filter algorithms for the autonomous on-orbit calibration of the star camera are developed. In the first algorithm, we estimate the attitude, principal point offset and the focal length with the help of two Kalman filters working in tandem. Occasionally, we find that the correlation of attitude and principal point offset can make this algorithm somewhat unstable. A novel algorithm has been developed to estimate the principal point offset and focal length by using measurements independent of attitude. The relative merits of the two algorithms are then studied for estimating the focal plane distortion and the attitude of a simulated spacecraft motion. Simulation results indicate that both algorithms produce precise attitude estimates by determining principal point offset, focal length and gyro bias or spacecraft angular velocity in case of gyro failure. However, reliability and robustness characteristics favor the second algorithm. An autonomous on-orbit calibration will not only make our calibration coefficients more robust to environmental disturbances but will also help to bring down the overall cost of the mission