A perpendicular magnetic recording head includes a main pole layer and a return path layer that are exposed from a medium-facing surface of the recording head facing a recording medium and that face each other with a predetermined gap therebetween at the medium-facing surface. The method includes limiting a number of R_RDYs sent between frames, when frames are waiting to be transmitted at a given time, for minimizing a number of ordered sets transmitted between frames. 89% by weight of a conjugated diene unit, 5 to 69. The predetermined desired position time history is verified by the control unit and by means of a preliminary filter and is modified with regard to the feasibility thereof if required. The mass of the film mirror is less than 40 g per square meter, capable of doubling and redoubling the generating power of solar energy equipment on a spacecraft, reducing significantly the weight of the system.