Here is the full list of all 12 Ion Assault achievements worth 200 gamerscore.
Complete the single player campaign.
Complete the cooperative campaign.
Destroy five asteroids at once.
Destroy seven asteroids at once.
Complete a stage without collecting a Power-Up.
Complete a whole sector without dying once.
Finish a stage in less than 90 seconds.
Score more than 500,000 points in a single game.
Score 1,500,000 points in a single game.
Survive 3 stages without dying once.
Collected enough Score Orbs in a single run to get two extra lives at once.
Destroy 50 big obstacles in a single game.