I've built it and unlocked JFK. Unfortunately, I can't tell you what tech allows you to build SETI, and as you probably already know, the Civilopedia is next to worthless, as the entry for the wonders don't even list the required tech. What I can tell you though, is that the required tech has to be a much earlier one than you'd expect for something like SETI, as the AI beat me to it several times as I was trying to unlock JFK, and this was on King, where I always had significantly more tech than any AI. Apparently I was just always missing the one tech I needed.