I recently got into a twitter discussion over the ISS attitude. The point of the discussion is the attitude that the ISS mantains while orbiting around the Earth.
From my reminescences of Oribital Mechanics, you need the highest inertia axis (usually the
y, for convention) to point towards the Earth, so that the gravitational differential pull will not affect too negatively the Attitude control (and as a neat consequence you can decouple the
x-z control loop from the
y one, plus you receive a side always pointing towards Earth for communication/observation) and I remember that it is somehow connected to the uncontrolled (and unexpected) spin of Explorer 1.
The other side argued instead that having a side pointing towards Earth is required to have this communication/observation side (i.e., cause and effect are inverted).
Which side is right? Why does the ISS always has the "cupola side" towards Earth?