Abstract: A system for determining the trajectory of a missile and the minimum miss distance with respect to a target aircraft, comprises two transmitters on the aircraft each cooperating with four receivers on the aircraft. Each transmitter radiates a succession of pulses each having a very short duration of the order of 2 nanoseconds and each having a shape approximating to a single sine wave. The transmitted pulses are reflected from the missile and received by the receivers each of which is accurately time gated so that the received signal is sampled at a predetermined time delay after the radiation of each transmit pulse. A time delay corresponds to a particular missile range, and by gating at different delays the sampled signals indicate when the missile enters or leaves a plurality of range envelopes surrounding the target. Processing of the sampled signals enables the missile trajectory and minimum miss distance to be computed.