Space radiation environment is composed by a variety of particles with energies ranging from keV to some GeV. These particles are either trapped into the magnetic field of the Earth or are passing through the Solar System. Some of the satellite electronics is based on silicon devices which suffer degradation due to environmental radiation. To study heavy ion and other particles effects we designed and fabricated MOS (metal oxide semiconductor) ad hoc capacitors. Radiation damage test were made using the Van de Graaf (TANDAR) heavy ion accelerator. In situ characterization was performed by means of C-V (capacitance-voltage) measurements during irradiation experiments and from the curves obtained the characteristic parameters were estimated.