1. A system for detecting the posture of a moving object in space comprising: a fixed electro-optical device of known orientation comprising at least one emission source, an image sensor and image analysis means; and an optical assembly comprising at least one optical retroreflector arranged on the moving object, wherein: the optical retroreflector is an optical sphere of variable index comprising a transparent hemisphere and a reflecting hemisphere such that a light ray, refracted by the transparent hemisphere, reflected by the reflecting hemisphere and refracted a second time by the transparent hemisphere re-emerges parallel to its direction of incidence, the optical retroreflector comprises a meshing comprising at least three opaque wires, of small thickness and known geometrical arrangement, the image of the optical retroreflector lit by the source forms a reflection on the image sensor, said reflection comprising at least the two images of the shadow of one of the three wires by the retroreflector, and the image analysis means detects at least the orientation of the leak line given by said images, said orientation being representative of 3 first parameter of the posture of the moving object.