it hit me. like a brick. no an anvil.
what is this purpose of Terra Nova Mira talks about? i think i know it. it was hinted at in the very first episode.
remember when Taylor said that he was the first man, but the second did not show up untill 118 days or so later?
this means time is not 100% synchronous between 2149 and Terra Nova. it would be almost stupid if it was, since messing about with the Time Hole would directly mean messing about with the time link itself. since messing about with the time hole already happens when they open it up, this means that at any time you could alter time.
this is one way, and it very likely is an engineering issue rather than a physics one.
so the purpose of Terra Nova: send people back in time, and then back to a future or past in the 2149 timeline.