1
$\begingroup$

Why can satellites not orbit around the North or South Pole, instead of orbiting about the centre of the earth?

$\endgroup$
2
  • $\begingroup$ On the chance that the answers are misinterpreting, highly inclined orbits are a thing. This means that the satelight orbits in a plane that includes the goemetric center of the Earth but also passes near the goemetric poles. Useful for mapping, global surface observations and spying. Such orbits are not stable in the long term due to high order moments of the planet, but they last for years. $\endgroup$ Nov 19, 2019 at 1:03
  • $\begingroup$ @dmckee, "Such orbits are not stable in the long term...", "...but they last for years." : Could you please explain how polar orbits being unstable last for years? Further, what does this statement mean "...high order moments of the planet..."? Thank you. $\endgroup$
    – Vishnu
    Nov 27, 2019 at 7:17

3 Answers 3

2
$\begingroup$

The sum of the gravitational forces on a satellite from all the atoms in the Earth is a net force toward the center of the Earth. (This is a consequence of spherical symmetry. It can also be shown by using integral calculus.) Thus any satellite’s orbit must accelerate toward the center and not toward, say, a pole.

$\endgroup$
0
2
$\begingroup$

Here is a diagram showing the orbit of a satellite around the North Pole.

enter image description here

The gravitational force $\vec F$ can be split into two components $\vec {F'}$ and $\vec {F''}$ such that $\vec {F}=\vec {F'} + \vec {F''}$.
The component in the plane of the orbit $\vec {F'}$ provides the centripetal acceleration around the North Pole $r\omega^2$.

However there is still the component $\vec {F''}$ to deal with as otherwise there will also be an acceleration of the satellite in the direction of this force.
One would need to have the satellite equipped with a rocket engine continuously providing a force equal in magnitude but opposite in direction to force $\vec {F''}$ to keep the satellite in the required orbit.
This is not a feasible proposition.

$\endgroup$
1
$\begingroup$

If we ignore the cases of elliptical orbits, the earth gives the satellite a gravitational attraction towards its centre, which is perpendicular to the velocity of the satellite. In your question, such a motion requires a force towards the poles of our earth, which is impossible to satisfy because a component force of the gravity would pull the satellite downwards and disrupt its original motion.

$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge you have read our privacy policy.

Not the answer you're looking for? Browse other questions tagged or ask your own question.