Attention! This achievement also connected with "Question of Faith" quest which will be given you by Eva in the Hort.
At the moment when you collect all nine notes - go to Eva in the Hort. She will help you with this puzzle and will make mark point on your map.
Then you must travel to this point and find a elevator.
Then you just need come to the code panel. Password to this panel you can find from puzzle with notes.
Now prepare to know all truth about Calaan.
And also you will get a cool photo :)
You will get achievement when you unlock all two code panels and walk around in this place.