Have there ever been any experiments measuring gravity in space above the rotational poles of any celestial body (Earth, Moon, Sun, etc.)?
I don't mean an orbit that passes near the rotational pole, but rather an orbital path that passes through the exact rotational axis?
And not on the surface of the celestial body, but in space - perhaps at the distance where satellites orbit the Earth or greater, however many miles above the surface that is.
The reason I ask is because from what I understand, satellites never orbit in a path that would cross through the axis. The reasons that I have heard are:
1. the data gathered from such an orbital path is relatively less helpful for GPS applications, and
2. there may be "relativistic effects" which make that path more difficult to transverse (whatever that means - it's over my head), and
3. in order to achieve such an orbital path, i would require more energy/fuel, making the satellite launch process much more expensive.
I assume that Newton's gravitational laws still holds in space along the rotational axis (b/c gravity is a function of mass and distance, not orientation with respect to rotation), but I was wondering if there have ever been any experiments to confirm it.
Also, what is meant by relativistic effects?