Great Fox
In order to unlock the Great Fox mission, you’ll need to have completed all of the main stages before completing the following sequence. Once you’ve completed all of the main stages, including the Fortuna stage, you’ll be notified that Star Wolf has been spotted in Sector Alpha. Make Fox and his team check it out and play through the stage, you should notice red laser fire then coming from your six.
Pigma from Star Wolf will appear and in order to get this mission, you’ll want to lock on to him with ZL. In doing so, Fox will leave the current mission and follow Pigma to a fight with Andrew and Pigma of Star Wolf. Defeat them both and you’ll be taken to the Great Fox and will play out a slightly different version of the Asteroid Field stage. The only difference here is that this stage features a different version of the Dodorah boss.
In order to defeat it, you’ll need to lure it in front of the Great Fox’s main gun and ensure it takes two hits from it. Once you’ve done this, you’ll unlock this handy shortcut to Sector Gamma.