One salient point might be that one of my explorer m5's scanned a number of the asteroids in the sector earlier on in the game, although afaik none of them were the ones needed for the mission.
Also, what is the final reward for OFF anyway, so far i've gained nothing but a sense of frustration and boredom. so if it's not all that good I might as well not bother with it. Flying hundreds of km around a needlessly large sector while swatting down endless swarms of khaak interceptors isn't my idea of a good time, certainly not for the measly 300k they're paying me for it...

Sorry if this has been mentioned/resolved elsewhere, but as this forum doesn't have the best search function in the world you'll just have to forgive me
