I’ve been able to create .raws from NASA’s .img files and I have constructed a fairly realistic landscape. I know I can add more then 1 terrain (eats up the processing power and ram, but as long as I am very careful not to add to much data at once, I think it can handle it after smoothing, etc. I’ve been loading .raws the size of 4096 pxls across, but I am trying to replicate a much bigger area. in its entirety (assuming my math isn’t off), a whole 1/27 of the moon I would like to simulate at once. I need it to be spherical however. Simply adding 9X4069 terrains and matching them up won’t cut it. I am wondering if there are other options such as wrapping around a big ass sphere. I am completely lost on how to do this, so I could really use some advice from the devs. Thank you for your consideration.
Default Unity terrain cannot be bended intro sphere, so you should to write your own terrain system with dynamic LoD topology, splat shader, grass, tree system etc.
I can say that this is very complicated task.
How would I go about doing that? I’m not an advanced programmer. Has any one else tried something like that? Could I create it in another program and import it? what are my options here?
The search term: “quad tree planet” in google will give you lots of valuable info. But you seem to tone down your technical level, and so I wonder if this is too big an undertaking for you?
Well, unless you want to actually just learn along the way. Because it’s surely not rocket science to get something like this going. But you need to put in an effort to get a solid and stable framework.
This task requires a huge programming skills. So maybe your option, is hire a programmer 
There is beatiful project for example http://en.spaceengine.org/
Also check a Youtube http://www.youtube.com/results?search_query=Real+Time+planet+rendering