Spherical UVs (or another practical way to create/ keep UVs)

Hello, congrats for the amazing work!

I want to replace the vertex colors with a baked texture, so i try to find a fast way to create the UVs. I tried to create spherical UVs in blender but they dont match exactly. 

1. Is there any way to keep the UVs , to export them with the mesh ?
2. If no , do they follow the spherical coordinates with center 0,0,0 ?

Thank you!