Two Earth's satellites move in a common plane along circular orbits. The orbital radius of one satellite `r=700km` while that of the other satellite is `Deltar=70km` less. What time interval separates the periodic approaches of the satellites to each other over the minimum distance?

Answer

`[(2pi)/(sqrt(GM))r^(3//2)(((r-Delta r)^(3//2))/(r^(3//2)-(r-Delta r)^(3//2)))]`