I'd just like to jump in here and point out that I really, really hate the UESPA. Not the concept - just the name. 'United Earth Space Probe Agency' - it just sounds so damn ridiculous, like something out of a cheesy pulp novel. Just like the dozen other names considered for the Enterprise
's operating authority in TOS - gems like 'Space Command', 'Star Service', etc. Those all sound just as stupid as UESPA, in some cases even more so. In fact I'm surprised the writers could even utter those phrases without laughing.
'Starfleet', on the other hand...that makes sense. Simple, honest, direct, *efficient*. And it DOESN'T sound like something from a pulp, or from stuff like "Rocky Jones, Space Ranger".