Spherical target state estimators

A spherical filter formulation is derived and the resulting nonlinear estimator is applied to a tactical air-to-air missile intercept problem. An Extended Kalman filter is used to estimate the target acceleration in the line-of-sight frame. The estimator models the target acceleration as a first-order Gauss-Markov process. A method suggested by Singer was used to select the process noise power spectral density matrix. Next, a kinematic constraint is used to improve the estimated target acceleration by using a fictitious measurement to augment the seeker measurements. Finally, a form of adaptive filtering is used to obtain a better value for the target acceleration time constant. These techniques are evaluated using a representative target engagement scenario.