Render textured terrain to large image

Hi guys!
I am working on some universe exploration game.
I have reached hard point and would like to get some help or advice.
So. I have generated terrain, textured it and placed some objects (rocks and other meshes).
Usually terrain is planet surface in my game. I want to texture planet (sphere) with whole terrain as texture.
Is there any asset or some way to achieve that?

(my weird and hacky way) I plan to make camera and render its viewport to image. Then I will map image to sphere as material.

Thank you in advance.

 

You might take a look at Sebastian Lague's YouTube series on Procedural Planet Generation to get some ideas - it is way cool.