As @Philipp points out in a comment to this question:
The general achievement contracts only appear when it's something you haven't already done yet.
To maximize my career performance I'd like not to go exploring before the corresponding achievement contract is available.
Some of this list, that I've already encountered in-game (as of 1.0.4) are:
- Orbit Kerbin
- Explore Mun
- Explore Duna
Is there a comprehensive list, so I could catch-em-all?