Abstract: Two Star-tracker-based attitude determination algorithms, the Least-Square algorithm (LS) and the quaternion estimator (QUEST) algorithm, are presented. This paper contains an accuracy comparison of the two algorithms under different number of the observation vectors and any bore sight direction of the star tracker in the global area. The results show that the QUEST algorithm is more accurate than the LS one, even under the adverse constellation configuration.

Key words: QUEST algorithm, Least-Square