The past year, 2012 has been the hundredth anniversary of the discovery of the cosmic-rays by Viktor Hess. It was also the tenth anniversary of the High Energy Stereoscopic System, in short H.E.S.S., named after him and last but not least 2012 also marked the start of the second phase of the experiment with the inauguration in September of a fifth and much larger telescope.
It was 1912, when Viktor Hess performed several flights in air balloon, and discovered the extra-terrestrial origin of ionizing particles bombarding the Earth. The cosmic-rays were discovered. Since then, they have attract attention of a large community of scientists: physicists, astrophysicists and astronomers. A new field of research, astro-particle physics, emerged, spanning several orders of magnitude both in energy and particle rate, with the aim of studying their origin and properties.