CALET, launched to the International Space Station in August 2015, is a calorimeter to measure cosmic rays and has been accumulating scientific data for over seven years. CALET measured the spectrum of the cosmic-ray proton from 40 GeV to 250 TeV. The tables of the spectrum measured by CALET are open to the public via DARTS in May 2023.

This helium data shows not only spectrum hardening which has been observed in light nuclei such as proton, carbon, oxygen, but also spectrum softening starting around 30 TeV is observed as observed in proton. It provides significant information for verifying the model of acceleration and propagation mechanism of cosmic ray in the galaxy. Because it is useful to discuss the data with past observations by other detectors, this result was published in Physical Review Letters on April 27, 2023.