Are some moons locked until I have enough hints from translations to find them?

Are some moons locked until I have enough hints from translations to find them?

Because like, in the big patch of unknown to the left of Iox, there’s a round bit in the center that I can’t get on the river to, but I’ve charted it out and it looks like there’s a path there. Is that river locked off to me whenever I try to go for it, if I haven’t got enough translations to make a plottable course for it?