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