Battle of Yavin? must be for rogue leader...
if you're talking about rogue squadron (the one that's out) they're bonus levels, umm...do u really wanna be spoiled? ok, you get hoth once u get gold medals in every level. there's 3 bonus levels, 1 for each type of medal u get on all the levels, all bronze gets u the first bonus level, all silver gets you the second bonus level, and all golds gets you the last bonus level.