You can't decline to activate a formation, so the spaceship
must make an activation roll.
From 1.6:
Quote:
The player going first then carries out an action with one formation, and then their opponent does likewise, and so on until all formations have taken an action. If one player runs out of formations to activate, then the opposing player may keep on activating formations one after the other until all of his formations have taken an action.
And 1.6.1:
Quote:
Note that you must activate a formation if you can, you can’t choose to pass unless you have no choice in the matter.
Bold formatting added by me.
From memory, the only exception is that formations already on Overwatch can stay in Overwatch without an activation test, but only if they are the last formation to activate.