Abstract: A system (30) for determining a missile kinematic property. The inventive system includes a radar system (36) for obtaining radar range measurements (34). An inertial reference unit (40) tracks changes in missile acceleration without the use of the radar range measurements and provides a signal (38, 42) in response thereto. An altitude Kalman filter (32) and a subtractor circuit (48) are used to combine the signal (38, 42) and the radar range measurements (34) to provide an accurate estimate (50) of the property. In a specific embodiment, the kinematic property includes missile vertical velocity and missile altitude. A radar system (36) supplies radar range information (34) to the Kalman filter (32). A loop (52) from the Kalman filter (32) to the radar system (36) facilitates estimating the radar range measurements (34) when invalid radar range measurements are provided by the radar system (36).