The wiki says that once you unlock Arbitrations, they are supposed to be unlocked forever, regardless of new mission nodes. I do have some Zariman and Deimos nodes from the quest hubs that I haven't done, but I swear those didn't count before. Plus supposedly you don't have to fully complete the star chart to unlock Arbitrations anymore.. I have recently got all planets and done all main story quests. I need to do some new war prep for mods with arbitrations.
![How to Unlock & what are Arbitrations [Warframe] YouTube](https://i.ytimg.com/vi/a4brOsYLILQ/maxresdefault.jpg "How to Unlock & what are Arbitrations [Warframe] YouTube")
Arbitrations are a special Alert variant hosted by the Arbiters of Hexis, featuring "elite" versions of endless missions with additional modifiers for greater difficulty. They were introduced in Update 23.10 (2018-10-12). As of update 39, Arbitrations are now unlocked through Junction completion instead of completing all Star Chart nodes. Arbitrations are now unlocked upon completion of a Task.. Arbitrations are special alert missions in warframe that feature higher level enemies and players only have one life. This mission is the main way of farming vitus essence which are the only way.