Errors in the trajectories of balistic missiles result from a number of causes such as the velocity uncertainty of the missile during its powered flight. Prediction of these errors provides the missile circular error probability (CEP) usually in the form of a ballistic position error ellipse that is derived for each trajectory. This ellipse can be used to significantly improve performance by reducing the error probability. At a particular time (T.sub.1) during the flight a radar altimeter determines the actual altitude of the missile and computation of the altitude error is made by subtracting the actual altitude from the nominal altitude at T. sub.1 provided by the predetermined ellipse. Range error is computed from the relationship &Dgr; h over tangent &thgr; where &thgr; is the angle of the ellipse semi-major axis with respect to the vertical. A missile control system then directs a maneuver based upon the range error to correct the error by returning the missile to its nominal trajectory.
展开▼
