Abstract: An aerodynamic body (M) provided with means for steering in response to a body control variable signal has a homing device (1) supplying a measurement signal (.epsilon..sub.m) of the error angle of the body. For intercepting a target (T) a computing unit (10), operating on the basis of relationships describing the aerodynamic behavior of the body with respect to the target, determines signal values (.sigma., .theta.) representing approximations of the line of sight angular rate (.sigma.) and the attitude angular rate (.theta.). The input signal to the computing unit (10) is the body control variable signal (u, u.sub.m) which is dependent on the determined approximation (.sigma.) of the line of sight angular rate. From said two signal values (.sigma., .theta.) a signal value (.epsilon.) representing an approximation of the error angle is determined. An error angle difference signal value (.DELTA..epsilon.=.epsilon..sub.m -.epsilon.