1. System for detecting the posture of an object which is mobile in space, comprising a fixed electro-optical device with a known orientation comprising at least one emission source, a photosensitive matrix sensor and at least one optical corner cube, which has a mask and is arranged on the mobile object, and of which the entry face of the mask has a predetermined geometry, the light coming from the source and reflected back by the corner cube forming a luminous contour corresponding to the reflection of the mask on the matrix sensor, wherein the fixed electro-optical device comprises an occulting optical element with a known shape and location, which is placed in the vicinity of the said source and is arranged so as to form a dark zone in the central part of the luminous contour, the detection system comprising analysis means arranged so as to determine the position and the orientation of the mobile object from knowledge of the vanishing points of the luminous contour and the position and shape of the dark zone.