Three Years of CALET Ultra Heavy Cosmic Ray Observations*

The CALorimetric Electron Telescope (CALET) has been collecting data on the International Space Station (ISS) since shortly after its launch in August 2015. Its main calorimeter (CAL), designed to measure the fluxes of the highest energy cosmic-ray electrons, has also made excellent measurements of cosmic-ray (CR) nuclei and gamma rays. CAL has measured energy spectra as well as secondary to primary ratios of the more abundant CR nuclei through ₂₆Fe, and it has the demonstrated dynamic range to measure CR nuclei from ₁H to ₄₀Zr. A high duty cycle (~90%) ultra-heavy cosmic-ray (UHCR) trigger provides an expanded geometric acceptance that is ~6× that for events fully contained by the CAL, which will collect in 5 years a UHCR data set with statistics comparable to that so far collected by the balloon-borne SuperTIGER instrument. Preliminary CALET results are in reasonable agreement with SuperTIGER relative abundances of even charge UHCR nuclei in a similar energy range, and both these measurements are complemented by the ~1/3 smaller lower-energy space-based ACE-CRIS measurements. Here we present the state of the analysis of ~3 years of this CALET UHCR data set and plans for future analysis steps.