(France / French) The protection of the astronauts against radiation is one of the main challenges that will face deep space exploration. On 18 August, ESA astronaut Thomas Pesquet activated the Lumina experiment inside the ISS as part of the ALPHA mission. Developed under the coordination of the French Space Agency, CNES, and with the involvement of CERN, the Laboratoire Hubert Curien at the Université Jean-Monnet-Saint-Étienne, and iXblue, this project uses two several-kilometre-long optical fibres as active dosimeters to measure ionising radiation in the ISS with very high sensitivity.