PURPOSE: To enable acquisition and tracing for a target even when the target flies at low attitude or it generates any deception or noise jamming against the rader radio wave.

CONSTITUTION: A first rader system 2a consisting of a transmitter 3a with one frequency band and receivers 4a and 4b with one and the other frequencies is located apart from a second rader system 2b consisting of a transmitter 3b with the other frequency and receivers 4a and 4b with one and the other frequencies. Then the first and second rader systems 2a and 2b are connected with a computer 5. Therefore the location of the target can be usually detected with a high accuracy, and even when the target flies at low attitude or it generates any deception or noise jamming against the rader radio wave, the system in which acquisition and tracing can be performed is realized.