General prefixes:
* Geo- (from Greek "ge", meaning "earth") - This is often used when referring to the Earth as a sphere, like "geodesy" (the science of measuring the Earth).
* Spher- (from Greek "sphaira", meaning "sphere") - This is the most direct prefix, but it's not as commonly used as some others.
* Globo- (from Latin "globus", meaning "sphere") - This is used to refer to the Earth as a sphere, like "globoid" (sphere-shaped).
Specific prefixes:
* Hemis- (from Greek "hemi", meaning "half") - This is used to refer to half a sphere, like "hemisphere".
* Astro- (from Greek "astron", meaning "star") - This is used to refer to celestial spheres, like "astrosphere".
The most appropriate prefix will depend on the specific meaning you're trying to convey.