Thanks all for your input,

I’ve found what works very well fsarchiver ! that can make live (or not) system backup awesome piece of software.

Thank you @IsoKiero@sopuli.xyz !
This is the solution.

unfortunately I can’t apply it, because the NAS is a closed proprietary 💩

@MrJameGumb@lemmy.world No you were right at first ! the question is

When they cross each other, which one is the closet to the earth ?

So indeed when they cross they are the same point in space (more or less otherwise it’s a collision :) ) so if they are at the same point the are at the same distance to Earth… :)

FYI great information about dual sim hardware type --> https://en.wikipedia.org/wiki/Dual_SIM#Types

Thank you @Are_Euclidding_Me@hexbear.net ! hooo so I can hide any post not only mine ! ok then it make more sense :D