I'm also curious about this. Isn't this exactly the kind of project Alphabet was created to wrap? i.e. something not related to Google's core business but still under the corporate umbrella?
Terra Bella is under Geo, which is where Maps resides. Seems like a pretty good fit to me, given that satellite imagery is presented in Maps. Why do you think Terra Bella should be in Alphabet?
That makes perfect sense actually. I was erroneously thinking of Terra Bella as a standalone project instead of as an extension to one of Google's core products.