A spacecraft is on a mission to explore Mars. When the spacecraft entered the Martian atmosphere, the commander made a balanced turn by tilting the spacecraft wings at an angle α to the horizontal. The commander maintained the center of gravity of the spacecraft in a horizontal plane. The speed V_s of the spacecraft was constant, and the spacecraft moved in a circle of radius R_s. Calculate the tilting angle α using V_s, Mars' gravitational acceleration g, and R_s. Note that the lift force is directed perpendicular to the wings and in the opposite direction of gravity.