Potential of the atmospheric monitoring system of JEM-EUSO mission

The existance of high energy particles with energies >1020 eV in the space is a basic problem in fundermental physics, because it means a violation of the GZK theoretical limitation. JEM-EUSO will try to detect such high energy particles in the space by the oprical fluorescence from the high energy paticles incident to the atmosphere. For caliblation of the optical background an atmospheric monitoring system consisting of a spaceborne lidar with an ultraviolet pulsed laser and an IR camera will be used. The IR camera takes images at suitable time intervals, monitoring the cloud cover in the whole field of view (FoV) of the telescope. Moreover stereo images are also taken to retrieve pixel by pixel the height of the cloud-top. The ultraviolet lidar measures the height of surface of clouds with the 30 m resolution. From these measuremnts we obtain a 3 dimentional map of clouds. The laser specifications are 20mJ/pulses at 355nm 20Hz rate, single longitudinal mode, and M 2<1 with conduction cooling.