Calet ultra heavy cosmic ray observations on the ISS

The CALorimetric Electron Telescope (CALET) on the International Space Station (ISS) has made cosmic-ray observations since shortly after its launch in August 2015. The heart of CALET, its main calorimeter (CAL), continues to make the direct measurements of the highest energy cosmic-ray total electron spectrum it was designed for. The CAL has also observed gamma rays and cosmic-ray (CR) nuclei, and it has measured energy spectra as well as secondary to primary ratios of the more abundant CR nuclei through ₂₆Fe. In addition, the CAL has measured the ultra-heavy cosmic ray (UHCR) nuclei heavier than ₂₆Fe, and it has demonstrated the dynamic range to measure CR nuclei from ₁H to ₄₀Zr. Using the main high energy (HE) CAL trigger mode particle energies can be reconstructed from the energy deposition in the total absorption calorimeter (TASC), and there is also a high duty cycle (~90%) UHCR trigger providing an expanded geometric acceptance that is ~6× that for events fully contained by the CAL. In ~5 years the UHCR trigger will collect a data set comparable to that so far collected by the balloon-borne SuperTIGER instrument. Preliminary CALET results presented at the last ICRC were in reasonable agreement with SuperTIGER relative abundances of even charge UHCR nuclei in a similar energy range. Both of these measurements are complemented by the ~1/3 smaller lower-energy space-based ACE-CRIS measurements. We present the current status and future plans for the CALET UHCR analysis.