Here is the full list of all 12 Ion Assault achievements worth 200 gamerscore.
Destroyed five asteroids at once.
Destroyed 50 big obstacles in a single game.
Finish a stage in less than 90 seconds.
Completed a stage without collecting a Power-Up.
Complete the single player campaign.
Complete the cooperative campaign.
Destroy seven asteroids at once.
Complete a whole sector without dying once.
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.