Status of the CALET Ultra Heavy Cosmic Ray Analysis

Abstract

The CALorimetric Electron Telescope (CALET) was launched to the International Space Station (ISS) on August 19, 2015, and has been returning science data since October 13, 2015. Through the main calorimeter (CAL), CALET observes the fluxes of high-energy electrons, gamma rays and nuclei. CALET measures the energy spectra of the more abundant cosmic-ray nuclei through 26Fe passing within the full CAL geometry, and utilizing an ultra-heavy cosmic-ray (UHCR) trig- ger, measures the relative abundances of the rare UHCR nuclei through ₄₀Zr with an expanded geometric acceptance. Preliminary analysis of the ₂₆Fe statistics from the first ~ 13 months of CAL data passing the UHCR trigger have validated the preflight estimate that in a 5 year mission CALET will observe comparable UHCR statistics to those achieved in the first flight of the Su- perTIGER balloon-borne UH experiment. The CALET UHCR measurements will complement those by SuperTIGER in a similar energy range without the need to correct for atmospheric inter- actions, as well as those at lower energy and with lower statistics by the space-based ACE-CRIS instrument. CALET is unique as an instrument sensitive to UHCR in having the dynamic range to measure from ₁H to ₄₀Zr. We present the status of the CALET UHCR analysis.