A system for measuring the radial speed of a moving body in a line of sight determined for a referential position is disclosed. The system includes an emitter assembly for emitting a signal and a referential receiver assembly dedicated to reception of the signal. The emitter assembly is disposed on a first of the elements of a group formed by the moving body and the referential position. The receiver assembly is disposed on a second of the elements of the group. The emitter assembly is able to emit a signal on at least two emission frequencies, where the emission frequencies are separated by a chosen emission frequency gap. The system also includes an analyzer configured to analyze the signal received by the receiver assembly, and to measure the reception frequency gap separating the signal reception frequencies to calculate the radial speed of the moving body according to a function of the reception frequency gap and emission frequency gap.