The main objective of this project is to develop a High Resolution Optical Satellite Sensor by using the synthetic aperture technique. This technique consists in the reconstruction of the original image of an object starting from that formed on the common focal plane of a set of telescopes (or a multi-aperture telescope) observing simultaneously the object while maintaining constant within a fraction of wavelengths the phase of the various wavefronts which are combined together (namely, a set of telescopes correctly co-phased, which, in this case, operate like an interferometer). The synthetic aperture technique thus allow to obtain the same resolution of a monolithic-mirror by means of a set of smaller mirrors properly arranged over the surface covered by the monolithic one, with a dramatic reduction of the volume and the mass of the optics. ISR participation will cover the control of the mirror positions.