The CALorimetric Electron Telescope (CALET) on the International Space Station: Results from the First Two Years On Orbit

Y Asaoka ,Y Tsunesada ,G Bigongiari ,W Ishizaki ,S Yanagita ,B F Rauch ,А А Моисеев ,Yosui Akaike ,S Okuno ,Y Katayose ,T G Guzik ,E Vannuccini ,R Sparvoli ,Simone Bonechi ,Misao Sasaki ,O Adriani ,S Nakahira ,Ichiro Takahashi ,Jun Nishimura ,J F Ormes ,S Sugita ,John F Krizmanic ,П Спиллантини ,N Mori ,S Ricciarini ,Ken Ebisawa ,A Yoshida ,A V Penacchioni ,Hiroyuki Murakami ,H Krawczynski ,J P Wefel ,Kentaro Asano ,M Mori ,Kunishiro Mori ,P Maestro ,K Kasahara ,Norita Kawanaka ,M Takayanagi ,Francesco Stolzi ,P S Marrocchesi ,Lorenzo Pacini ,M Ichimura ,C Kato ,Yuki Shimizu ,Y Kawakubo ,J Kataoka ,V Pal'shin ,H Motz ,Y Uchihori ,C Checchia ,M L Cherry ,A Shiomi ,S Ueno ,T Tamura ,J E Suh ,W R Binns ,T Lomtadze ,Kazuhiro Sakai ,N Cannady ,M G Bagliesi ,M H Israel ,Nobuyuki Hasebe ,T Terasawa ,J W Mitchell ,P Papini ,H Tomida ,Shoji Torii ,P Brogi ,K Yamaoka ,Ryuho Kataoka ,M Bongi ,T Sakamoto ,T Hams ,A Messineo ,N Tateyama ,H Fuke ,A Bruno ,Shoko Miyake ,E Berti ,M Takita ,A Sulaj ,V Di Felice ,F Palma ,J H Buckley ,G A De Nolfo ,Kunihito Ioka ,S Ozawa ,K Hibino ,G Collazuol ,G Castellini ,Kazunori Kohri ,K Munakata ,Kenji Yoshida

doi:10.1088/1742-6596/1181/1/012003

Abstract

The CALorimetric Electron Telescope (CALET) is a high-energy astroparticle physics space experiment installed on the International Space Station (ISS), developed and operated by Japan in collaboration with Italy and the United States. The CALET mission goals include the investigation of possible nearby sources of high-energy electrons, of the details of galactic particle acceleration and propagation, and of potential signatures of dark matter. CALET measures the cosmic-ray electron+positron flux up to 20 TeV, gamma-rays up to 10 TeV, and nuclei with Z=1 to 40 up to 1, 000 TeV for the more abundant elements during a long-term observation aboard the ISS. Starting science operation in mid-October 2015, CALET performed continuous observation without major interruption with close to 20 million triggered events over 10 GeV per month. Based on the data taken during the first two-years, we present an overview of CALET observations: 1) Electron+positron energy spectrum, 2) Nuclei analysis, 3) Gamma-ray observation including a characterization of on-orbit performance. Results of the electromagnetic counterpart search for LIGO/Virgo gravitational wave events are discussed as well.

Highlights

The CALorimetric Electron Telescope (CALET) [1, 2] is a high-energy astroparticle physics mission on the ISS, with development and operation conducted by Japan in collaboration with Italy and the United States
The unexpected increase of the positron fraction above 10 GeV established by PAMELA [12] and AMS-02 [13] may require a primary source component for positrons in addition to the generally accepted secondary origin. Candidates for such primary sources range from astrophysical to exotic
Since these primary sources emit electron-positron pairs, it is expected that the all-electron spectrum would exhibit a spectral feature, near the highest energy range of the primary component

Summary

Introduction

The CALorimetric Electron Telescope (CALET) [1, 2] is a high-energy astroparticle physics mission on the ISS, with development and operation conducted by Japan in collaboration with Italy and the United States. The components and read-out sensors are summarized in the left panels of Fig. 2 Combining these sub-detectors as well as the trigger system and data acquisition system, the CALET instrument features (1) a proton rejection factor larger than 105, (2) a 2% energy resolution above 20 GeV for electrons, (3) very wide dynamic range from 1 GeV to 1 PeV, (4) charge resolution of 0.1–0.3 electron charge unit from protons to above iron (up to Z = 40), (5) an angular resolution of 0.1 to 0.5◦, and (6) a geometrical factor of the order of 0.1 m2sr. Data transmission from JAXA-GSE to WCOC and data processing for scientific analysis at WCOC proceeded smoothly

Calibration

Results

Summary and Prospects