Atmospheric scattering with dynamic transparency

Complicated yes, I am looking for someone who is good with shaders for this. I already have the atmopsheric scattering shader, and i've already seen 16-2 gpu gems, but i'm looking to add a dynamic layer for transparency to the shader. The farther you get from the surface of the planet (atmosRadius - planetRadius), the more transparent the atmosphere becomes.

When you are on the surface of the planet, you cannot see the sky and stars (particle effect and models)

When you are x units above the planet surface, you can see the stars and planets through the atmosphere.