The Calorimetric Electron Telescope (CALET) Project

The CALorimetric Electron Telescope, CALET, mission is proposed for the Japanese Experiment Module Exposed Facility, JEM-EF, of the International Space Station. The scientific objective is to investigate the origin of the cosmic electrons and gamma-rays in very high energy region. The detector is composed of an imaging calorimeter of scintillating fibers and a total absorption calorimeter. The thickness of all absorber is 36 r.l for electro-magnetic particles and 1.7 m.f.p for protons. Total mass of the payload is nearly 2,500 kg, and the effective geometrical factor is 0.5 -1.0m(2) sr. The detector is capable of measuring the electrons from a few GeV to 10 TeV and the gamma-rays from 20MeV to several TeV, keeping the energy resolution within a few % over 10 GeV. The hadron rejection power should be nearly 106 in order to observe the electrons up to 10 TeV and it is achieved by measuring the fine structure of shower development. Much higher hadron-rejection power in the gamma-ray observation could be easily attained by the anti-conincidence counter covering the detector. Observation of protons and heavy nulei from 1 to 1000 TeV is also consedered to investigate the acceleartion limit in supernova shocks. We are expecting to launch the CALET around 2010 by the Japanese H-II Transfer Vehicle, HTV.