Here is the full list of all 28 Firmament achievements.
Dropped five ice blocks with the skiff in Curievale
Read every document in Firmament
All Worlds Must Collide
Triggered every Mentor speech
Engaged the Embrace in Curievale
Solved the dive suit puzzle in Curievale (trigger when you get to the airlock at the end)
Powered the furnace in Curievale
Explored the bunker in Juleston
Engaged the Embrace in Juleston
Lowered the water in the reservoir in Juleston
Engaged the Embrace in St. Andrew
Lowered the water in the reservoir in St. Andrew
Raised spire in St. Andrew
Got the Amplified Force upgrade
Called the Camelus for the first time
Accessed the elevator in the conservatory in St. Andrew
Raised spire in Juleston
Got the Concatenated Socketing upgrade
Raised spire in Curievale
Got the Distance Extension upgrade
Picked up an ice block with the HUG
Crushed some ice in Curievale
Visited Juleston for the first time
Added the missing piece to the skiff puzzle in St. Andrew
Visited St. Andrew for the first time
Visited The Swan for the first time
Raised the starting bunker
You were Awakened in the bunker