Status of the operations of CALET for 7.5 years on the International Space Station

Abstract

The CALorimetric Electron Telescope (CALET) has successfully been carrying out cosmic-ray observations on the International Space Station since October, 2015. CALET directly measures the cosmic-ray electron spectrum in the energy range of 1 GeV to 20 TeV with a 2 % energy resolution above 30 GeV. In addition, the instrument can measure the spectrum of gamma rays well into the TeV range, and the spectra of protons and nuclei up to a PeV. The scientific operations are implemented by taking into account orbital variations of geomagnetic rigidity cutoff. Scheduled command sequences are used to control the CALET observation modes on orbit. The high-energy (> 10 GeV) trigger mode is always active for maintaining maximum exposure to high-energy electrons and other high-energy shower events. Also, around the ISS orbit, calibration data acquisition by, for example, recording pedestal and penetrating particle events, a low-energy electron trigger mode operating at high geomagnetic latitude, a low-energy gamma-ray trigger mode operating at low geomagnetic latitude, and an ultra-heavy trigger mode, are scheduled. As of June 30, 2023, the total observation time is 2818 days with a live time fraction of the total time around 86 %. Nearly 1.86 billion events are collected with the high-energy trigger.