Incorporating delayed star tracker measurements in Gokturk-2 satellite attitude filter

Star trackers (STRs) are widely used for fine attitude estimation. Due to the processing time for tasks such as star identification, track-ing, and attitude solution, a STR can provide the attitude quaternion measurements with a time delay, which may be as high as a few 100 ms. Different methods are available for incorporating such delayed measurements in the attitude filter, such as the most straightfor-ward method of propagating the measurements to the actual filter time. This study evaluates different methods to incorporate the delayed STR measurements in the Gokturk-2 satellite attitude filter, which is structured as a Multiplicative Extended Kalman Filter (MEKF). Methods are compared in terms of accuracy, computational load, and impact on the filter's optimality. They are evaluated using the simulated data for an Earth observation spacecraft in Sun-synchronous orbit and the actual STR data for the operational Gokturk-2 satellite. & COPY; 2023 COSPAR. Published by Elsevier B.V. All rights reserved.