Extension of the spacecraft launch windows to determinate accessible areas on the Venus surface in the frame of the Venera-D project

The paper considers the problem of finding accessible areas on the Venus surface and the prospect of their increasing by extension of launch windows during the period from 2026 to 2031; taking into account the restrictions on the payload weight and the maximum overload level affecting the lander during the descent in the Venus atmosphere. The project of the Venera-D mission is used as the initial data for the work. The possibility of reaching the planet on the first and second half-turns of the heliocentric transfer orbit is analyzed. As an example, the effect of the launch window expansion for 2031 on the nature of changes in the accessible landing areas is considered. Possible payload weight expenses for launch window expansion are estimated. The launch windows are selected by solving the Lambert problem, where the transit spacecraft momentum near the Earth for the flight to Venus along the first and second half-orbit paths at the period from 2026 to 2042 is calculated. The accessible landing area is shown when increasing the launch windows initially adopted for 2031.The estimation of payload weight expenses for increasing the launch windows is performed.