English: The crust-mantle boundary variation could bring effect to the orbit of spacecraft due to the higher density of mantle and lower density of crust. When there is thinner crust, there would be greater gravitational pull from the mantle due to its more massive nature. As a result, it would shift to an orbit with lower altitude. And if the crust is thick, the gravitational force experienced by the spacecraft would be less and the orbit would be at a higher altitude.