Blueprint detector? 
Edit: Oh, it’s projector, my mistake.
To what purpose? Projecting base layouts for other players to see? I can’t think of any other thing by using that name and what we know of multiplayer…
Perhaps maybe it’s just a visual representation for why there’s a ghost image of base parts before placing them?
Most of all I’m still curious how some of these travellers are going to get their helmets on
I’m going to assume we don’t look like the travellers we’ve met, maybe we’re finally the closest instance to its creators.