GAMMA-400 Gamma-Ray Observations in the GeV and TeV Energy Range

The future space-based GAMMA-400 γ -ray telescope will operate onboard the Russian astrophysical observatory in a highly elliptic orbit during 7 years. Observing γ -ray sources from Galactic plane, γ -ray bursts, γ -ray diffuse emission, γ rays from the Sun, and γ rays from dark matter particles will be performed uninterruptedly for a long time ( ∼ 100 days) in point-source mode in contrast to scanning mode for Fermi-LAT and other space- and ground-based instruments. GAMMA-400 will measure γ rays in the energy range from ∼ 20 MeV to several TeV units, have the unprecedented angular ( ∼0.01^∘ at E_γ=100 GeV) and energy ( ∼2% at E_γ=100 GeV) resolutions better than for Fermi-LAT, as well as ground-based γ -ray facilities, by a factor of 5–10, and perfectly separate γ rays from cosmic-ray background.