Observation of Ultra-High Energy Cosmic Rays in cloudy conditions by the JEM-EUSO Space Observatory

Source of Ultra-high Energy Cosmic Rays (several times 10 19 eV) are still unidentified. Overcoming their extremely small fluxes, a detector with huge observation are as is needed to investigate the energy and arrival direction distribution of EECRs. JEM-EUSO is a unique experiment that will be located in the International Space Station to observe extensive air showers (EAS) by monitoring night part of Earth atmosphere. In addition to clear sky condition, the extensive air showers in cloudy condition are also observable by taking advantage of the certain fraction of EAS develop above the cloud. In the preset work, using Monte Carlo simultions for test clouds, the cloud impact to the trigger efficiency was estimated taking into account the statistics of cloud property.