A control device (D), for a spacecraft (S1) of a group of spacecraft moving in formation, comprises i) an assembly consisting of three antennas (A1-A3) installed on a face of the spacecraft (S1) and capable of emitting and/or receiving first and second RF signals exhibiting first and second frequencies spaced apart by a chosen frequency gap, ii) first measurement means (M1) charged with determining first and second differences in path length between antennas (A1-A3), corresponding to the first frequency and to the frequency gap, on the basis of the first and second signals received by the antennas and originating from another spacecraft, iii) second measurement means (M2) charged with delivering measurements of rotation undergone by the spacecraft (S1), and iv) processing means (MT) a) charged with coarsely estimating the direction of transmission of the signals received on the basis of first and second initial path length differences, b) with ordering the positioning of the spacecraft (S1) so that a chosen axis of a frame of reference tied to said spacecraft is aligned with respect to the coarse direction of transmission, c) with ordering the rotational turning of the spacecraft (S1) about the chosen axis, d) with precisely estimating the direction of transmission of the signals emitted by the other spacecraft (Si′) on the basis of the rotation measurement and of a measurement of variation of the first path length difference induced by this rotation.