  The High-Energy Ray Observatory (HERO) is a space experiment based on a heavy
ionization calorimeter for direct study of cosmic rays. The effective
geometrical factor of the apparatus varies from 12 to 60 m$^2$sr for protons
depending on the weight of the calorimeter from 10 to 70 tons. During the
exposure for $\sim$5 years this mission will make it possible to measure energy
spectra of all abundant cosmic ray nuclei in the knee region ($\sim$3 PeV) with
individual resolution of charges with energy resolution better than 30\% and
provide useful information to solve the puzzle of the cosmic ray knee origin.
HERO mission will make it also possible to measure energy spectra of cosmic
rays nuclei for energies 1-1000 TeV with very high precision and energy
resolution (up to 3\% for calorimeter 70 tons) and study the fine structure of
the spectra. The planned experiment launch is no earlier than 2029.
