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Posted on 2/14/17 at 5:04 pm to beantown
quote:
Thought it was a fixed path once it got up there, hence the question.
Nope. The Earth is not a perfect spheroid and there are parts of it that are more dense than others (for instance, the Himalayas). This means that the gravitational field of the Earth is not perfect either and varies. On the surface, this is absolutely measurable, but it has no really noticeable effect since things like friction and air resistance swamp the effects of the tiny differences in gravitation.
However, way out in geosynch orbit, things like tiny differences in gravity matter. As the satellite moves around the planet, these tiny differences in gravity tug the satellite ever so slightly in different directions from orbit to orbit. In addition, the moon's tug on the satellite varies as they both revolve around the Earth and the distances and the angles change. Even things like the pressure of the sun's light on the satellite varies as the angle the sunlight hits the satellite changes and it travels into the planet's shadow. All these tiny little pushes and tugs add up over time to move the satellite away from the station it should be keeping above the Earth. Every so often, the satellite operator plans a small adjustment burn to keep the satellite where it should be.
Now, you can't just leave a dead satellite in geosynchronous orbit because it would endanger other satellites if it drifts free and because, for operational reasons, there are a limited number of slots where a satellite can be stationed in that particular orbit. So, there's an agreement that all measures will be taken to put the satellite into a graveyard orbit where it won't interfere with anything once the operator is done with it. Many satellites that are operating perfectly are scrapped when the normal station keeping depletes their fuel to the point where there's only enough left to get it to the graveyard orbit.
This post was edited on 2/14/17 at 5:06 pm
Posted on 2/14/17 at 5:05 pm to beantown
Posted on 2/14/17 at 5:29 pm to MountainTiger
Correct / they are all over the equator. I was referring to the satellites at the orbital slots between roughly 60-130 degrees west. That's typical called the US domestic arc.
Posted on 2/14/17 at 5:52 pm to Atttaboy
I figured you knew what you were talking about. Just being a little pedantic. 
Posted on 2/14/17 at 7:58 pm to beantown
Even when they are not in serious maneuvers, they are actually moving in a small Figure-8 pattern throughout their life, but centered at their orbital slot. Their center position is called "center of box."
For the commercial Fixed Satellite Service satellites, their separation is typically 2 degrees.
LSU ChE and not using any of the Chem part for sure...
For the commercial Fixed Satellite Service satellites, their separation is typically 2 degrees.
LSU ChE and not using any of the Chem part for sure...
Posted on 2/14/17 at 8:59 pm to Atttaboy
Great responses. Exactly what I was looking for 
So many little things contribute to it working. I love engineering!
So many little things contribute to it working. I love engineering!
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