Modification of orbit "Tundra" for service in Russia and its stability analysis

Based on long term sustainability analyses of orbital constellation of "Sirius" satellites, orbiting earth on high elliptic "Tundra" orbits was determined period of constellation functioning without necessity of orbital correction. Further orbit analysis is in progress in order to modify orbital parameter and optimize Russian Territory coverage. Modified orbital structures that consist of three and four satellites being compared. Beamwidth required in order to cover work area of spacecraft trajectory in the interval between orbit corrections were estimated for ground station with fixed antenna orientation.