This part of the rules (All Errors Are My Own, p. 10) confuses me too: "Applying the mission control impact is tied to the crew impact applied at the same time: if a crew member wishes to get the crew impact, they must also apply the mission control impact, and if they want the mission control impact, they must apply the crew impact. The crew can elect to not have either impact affect them."
This seems to indicate there are separate crew impacts and mission control impacts, but I can't find crew impacts anywhere in the rules...