Comments on "Optimal guidance of proportional navigation"

The author comments on the work of P.-J. Yuan (ibid. vol. 33, pp. 1007-1011, 1997) in which involved with the target motion parameters seem to have been ignored. In practice, the contact is obtained when the target tracking is on and target motion parameters (range, course, bearing, speed, and acceleration of the target) are found out. Various sophisticated versions of Kalman filter generate estimates with minimum variance. As long as the measurements are corrupted with noise, the estimates contain errors and these are described by covariance matrix of the estimated target state vector.