<h2>AAS 95-421</h2><h2>Optimal Guidance and Nonlinear Estimation for Estimation of Accelerating Targets</h2><h4>M. E. Hough, Textron Defense Systems, Wilmington, MA</h4><h2> Abstract </h2>Optimal guidance and nonlinear estimation algorithms are formulated for interception of an accelerating target vehicle during boost.  For an interceptor with two-axis control of translational acceleration, time to go may be selected to null the component of commanded acceleration along the uncontrolled axis.  A nine-state, extended Kalman filter is formulated, in a Cartesian-inertial frame.  The filter dynamics model includes a vector-differential equation for the thrust acceleration vector of the target during a gravity-turn maneuver.  With angle measurements from a strapdown seeker, very small miss distances can be achieved, despite large estimation errors in range, because of the time-to-go algorithm.  Based on Monte Carlo simulations, theoretical collision probabilities are determined for different sensor measurement accuracies and filter update rates.<br><br>