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?

Explanation

Let `omega=sqrt((gammaM_E)/(r^(3.)))=` circular frequency of the satelline in the outer orbit,
`omega_0=sqrt((gammaM_E)/((r-Deltar)^3))=` circular frequency of the satellite in the inner orbit.
So, relative angular velocity `=omega_0+-omega` where -sign is to be taken when the satellites are moving in the same sense and +sign if they are moving in opposite sense.
Hence, time between closest approaches
`=(2pi)/(omega_0+-omega)=(2pi)/(sqrt(gammaM_E)//r^(3//2))(1)/((3Deltar)/(2r)+delta)={(4*5,days,(delta=0),,),(0*80,hour,(delta=2),,):}`
where `delta` is 0 in the first case and 2 in the second case.