The CALorimetric Electron Telescope (CALET) on the ISS: Preliminary Results from On-orbit Observations since October, 2015

Abstract

The CALorimetric Electron Telescope (CALET) on the ISS: Preliminary Results from the On-orbit Observaion since October, 2015 The CALorimetric Electron Telescope (CALET) space experiment, which has been developed by Japan in collaboration with Italy and the United States, is a high energy astroparticle physics mission to be installed on the International Space Station (ISS). The primary goals of the CALET mission include investigating possible nearby sources of high energy electrons, studying the details of galactic particle propagation and searching for dark matter signatures. During a two-year mission, extendable to five years, the CALET experiment is measuring the flux of cosmic-ray electrons (including positrons) to 20 TeV, gamma-rays to 10 TeV and nuclei with Z=1 to 40 up to 1,000 TeV. The instrument consists of two layers of segmented plastic scintillators for the cosmic-ray charge identification (CHD), a 3 radiation length thick tungsten-scintillating fiber imaging calorimeter (IMC) and a 27 radiation length thick lead-tungstate calorimeter (TASC). CALET has sufficient depth, imaging capabilities and excellent energy resolution to allow for a clear separation between hadrons and electrons and between charged particles and gamma rays. The instrument was launched on August 19, 2015 to the ISS with HTV-5 (H-II Transfer Vehicle 5) and installed on the Japanese Experiment Module-Exposed Facility (JEM-EF) on August 25 . Since the start of operation from mid-October, 2015, continuous observation has been conducted without any major interruption mainly by triggering high energy (>10 GeV) showers. The number of triggered events is about 20 million per month. By using the data obtained so far, we will present a summary of preliminary results by the CALET observations on 1) Electron energy spectrum, 2) Proton and Nuclei spectum, 3) Gamma-ray observations, with results of the performance study on orbit. We also present the results of searches for the electromagnetic counterparts to LIGO-VIRGO gravitational wave events and high energy counterparts to GRB events measured with the CALET Gamma-ray Burst Monitor (CGBM).