# Satellite with period equal to that of its planet?

1. Apr 21, 2013

### Humaj

Would it be possible to have a satellite orbiting Earth slowly enough that it always stays between Earth and the sun? Not necessarily directly between so that its shadow is always on Earth, but such that, with an orbit that would take it "behind" Earth, it would orbit at a speed such that when it gets halfway through its orbit, Earth has gone halfway through its own, and its still on the inside of Earth's orbit? Probably much farther away than geosynchronous satellites?
This wouldn't be the same thing as an L1 point in my understanding of Lagrange points, because the object is solely in orbit around Earth, but might not be possible.
And please be specific as to why it's not possible if it's not, so I know whether to go with a fabricated excuse as to how it could be possible, or go with an actual possible story.

2. Apr 21, 2013

### mathman

I suggest you could calculate the distance and see if it makes sense. My guess (I can be completely wrong) is that it would be as far away as the sun, since planetary orbits depend almost entirely on the distance from the sun.

3. Apr 21, 2013

### phyzguy

Why do you say this isn't the Lagrange point L1? In order to stay between the Earth and the Sun, it needs to orbit both the Sun and the Earth. Relative to the fixed stars, in one year, it will have made one orbit around the Sun, and it will have made one orbit around the Earth. I think this is what is meant by the Lagrange point L1. So the answer is, yes it is possible.

4. Apr 22, 2013