# Orbiting space station is observed to remain always vertically above

## Main Question or Discussion Point

Why is it that if an orbiting space station is observed to remain always vertically above the same point on Earth then the observer must be on the equator of Earth?

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DaveC426913
Gold Member
Why is it that if an orbiting space station is observed to remain always vertically above the same point on Earth then the observer must be on the equator of Earth?
Why do you think?

Dale
Mentor
Strictly speaking the statement isn't true. The observer doesn't need to be on the equator, but the point above which the geosynchronous space station remains stationary must be on the equator. (I am having trouble telling if I wrote that correctly)

DaveC426913
Gold Member
Here's a hint:
http://smithplanet.com/stuff/orbiter/dockingimages/mapMFD.jpg" [Broken] is a (randomly Googled) world map with some orbits superimposed on it. Why do the orbits seem to follow nice sine waves instead of straight lines? What properties of the two orbits illustrated would cause the two sine waves to have different amplitudes (heights)?

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The thesis is wrong. The orbit of the space station will always around the core of the Earth but not neccesarily around the equator. You will see the space station always above you if it has the same angular velocity as the Earth. For example telecommunication satellites work like this. They are put into orbit by high powered rockets so that they have angular velocity the same as that of the Earth.

DaveC426913
Gold Member
The thesis is wrong. The orbit of the space station will always around the core of the Earth but not neccesarily around the equator. You will see the space station always above you if it has the same angular velocity as the Earth. For example telecommunication satellites work like this. They are put into orbit by high powered rockets so that they have angular velocity the same as that of the Earth.
I am not sure what this person is talking about. There's some misleading info here.
1] What thesis?
2] A satelllite will NOT always be above you if it isn't in an equatorial orbit.

D H
Staff Emeritus