Results from the ULTRA experiment in the framework of the EUSO project

The detection of ?erenkov light from EAS in a delayed coincidence with uorescence light gives a strong signature to discriminate protons and neutrinos in cosmic rays. For this purpose, the ULTRA experiment has been designed with 2 detectors: a small EAS array (ETscope) and an UV optical device including wide field (Belenos) and narrow field (UVscope) ?erenkov light detectors. The array measures the shower size and the arrival direction of the incoming EAS, while the UV devices, pointing both to zenith and nadir, are used to determine the amount of direct and diffused coincident C erenkov light. This information, provided for different diffusing surfaces, will be used to verify the possibility of detecting from Space the ?erenkov light produced by UHECRs with the EUSO experiment, on board the ISS.