The main goal of the High-Energy Ray Observatory (HERO) mission is to perform direct measurements of very high energy cosmic ray. Measurements will concern the following scientific goals: detailed study of charge composition of CR in knee region, studies of the energy spectra of Galactic and extragalactic CR, search for signatures of dark matter particles. HERO is planned to be launched onboard a heavy satellite. This experiment is based on the application of a wide aperture (>2π) deep (~5λ) ionization calorimeter. The effective geometrical factor of the apparatus is not less than 8-16 m2sr depending on the type of particles. Under the long exposure (~10 years), this mission will make it possible to precisely measure cosmic rays up to 1017eV. Wide Monte-Carlo simulations were performed to obtain instrument response for different species of cosmic rays, including charged particles and gammas.