This is an ambitious adventure, which packs in a lot of worldbuilding and plot. Lovely bit of pathos at the end! I love the crunchy elements of resource management, and nicely developed mechanisms for exploration.
It might be nice to have a timeline/overview of events to make it easier to see at a glance how the premise is set up. Likewise developing the visuals as others have mentioned.
Have you considered that the way re-rolls work on major and minor events means that exposition will become slower as the mission goes on? (It would give a sense of getting further from civilisation, so if that's the intent then please ignore this!) It might be better to switch these around so that you start by rolling on minor events, and if that minor event has already come up receive a major event instead, so that you gather pace instead?
Overall, lovely bit of storytelling that I would enjoy playing through :)