Abstract: | Two-state tracking filters are considered for seeker applications. Estimation of the line-of-sight (LOS) rate is the main purpose and equations of motion for the LOS are discussed and simplified for design. An observer approach is applied, the filter transfer functions are given and the gain is designed by pole placement. Also a measurement time delay is taken into account. The filter properties are investigated for deterministic LOS rotations, which is a case of practical interest, corresponding to target maneuvers. The influence of measurement noise is also considered |