You are going away, to some place isolated… in space, of course. You will only be around one other person. You can take an allotment if 1GB of personal media with you (text, video, music, games, pics, etc.) that you will be able to access in your free time indefinitely at will.
The other person will also take 1GB with them, but you won’t be able to talk to them until you’re on the journey.
You will have access to any knowledge resources to perform your function and keep you alive. You will never return to a point where you can get new external media. Any additional media you ever access would have to be created by you and or your travel partner with what you have access to.
You will also not know the sex of your partner, but they have willingly taken the same risks to embark on the journey as yourself, and will have a similar mission.
Since size is paramount, I’d probably fill about half of this space with NES, GB, and SNES roms and the emulators to play them as well as a few highly replayable classic PC games (CIv, SIm City, X-Com, Warcraft 2, Doom) and some small programs to edit/create images, and a small compiler and text editing tool (maybe Pascal based as another commenter suggested). The rest would be filled with a tremendous amount text books in a compressed archive, both fiction and non-fiction.