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