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.1 for electro-magnetic particles and 1.7m.f.p for protons. Total mass of the payload is nearly 2.500kg, and the effective geometrical factor is 0.5-1.0m₂sr. 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 10TeV 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.