# Geostationary Satellite Equatorial Plane

Geostationary satellites need to be in equatorial plane.

Now my first doubt is what exactly is the equatorial plane?
Is it just locus of all points have 0 latitude
or locus of all points having a fixed latitude say 5.
{Like does a orbit in equatorial plane mean that its latitude is 0 degree
or does it mean that the latitude is constant throughout the orbit not necessarily 0 like say 15)

Also if the answer is that the latitude is just 0 and not anyither fixed value then please explain why a geostationary orbit cannot have an orbit in any other latitude as i feel it still will have the required time period and would appear stationary at all times.

D H
Staff Emeritus
The center of the Earth must lie on, not above or below, the orbital plane of a satellite.

Okay...But why is this a requirement for the satellite to be stationary.

Like let the satellite be at 5 latitude having the required w(omega) and thus the required height.

Still at all times it will appear stationary to the observer on the earth isn't it?

By 5 latitude I mean 5 degree latitude.
Always at 5 degree.
So no problem of the satellite being seen as going up and down.

Infact to be straight forward my question is why is 0 degree latitude orbit a necessity for the satellite to be geostationary

D H
Staff Emeritus
A satellite cannot orbit so it is always at 5 degrees latitude.

I didnt get you!

I meant to say it rotates around the earth at 5 degree latitude
the longitude is changing

And by stationary i mean geo stationary

Like why is that the orbital plane should be the equatorial plane ?
Why not the plane of tropic of cancer or any other latitude?

Hello Dh, I still haven't got the reason why the satellite has to be in equatorial plane for it to appear stationary relative to earth.

Why can't it be in a plane parallel to the equatorial plane.
For eg why cant it be in the plane of tropic of cancer for it to be stationary relative to earth

Drakkith
Staff Emeritus
Hello Dh, I still haven't got the reason why the satellite has to be in equatorial plane for it to appear stationary relative to earth.

Why can't it be in a plane parallel to the equatorial plane.
For eg why cant it be in the plane of tropic of cancer for it to be stationary relative to earth

Because it's orbit would not be centered on the center of the Earth. The Earth's center of mass is the focus of the orbit, meaning that any satellite must orbit around that point, nowhere else. To clarify realize that the Earth is pulling on the satellite through gravity with the force of the pull towards the center of the Earth. If a satellite started out in an orbit that would be stationary relative to the Tropic of Cancer, the Earth's gravity would pull it into a different orbit. It's simply not possible without constantly expending fuel to stay in the right spot, as you would have to work against gravity.

Oh got it.Thanks a lot
The only reason its done is to save energy, right?

However (hypothetically) if I am willing to spend energy(maybe using solar panels)
then tropic of cancer can be an orbital plane.
Am i right?Just clarifying.

Drakkith
Staff Emeritus
Oh got it.Thanks a lot
The only reason its done is to save energy, right?

However (hypothetically) if I am willing to spend energy(maybe using solar panels)
then tropic of cancer can be an orbital plane.
Am i right?Just clarifying.

Not energy, fuel. Our only available means of propulsion involves ejecting mass from a vehicle. IE things like rocket engines or nozzles that allow gas to escape. Mass and space on the satellites is VERY limited, and they generally carry just enough for small changes to stay in their orbits to counteract drag or gravitational effects. Something like a stationary orbit over one of the Tropics is simply way beyond feasible.

Oh yeah.Excellent point.
Thanks a ton Drakkith.