Here is the full list of all 11 Oscillatron: Alien Frequency achievements.
Destroy 100 purple spaceships
Destroy 50 purple spaceships
Destroy 100 red spaceships
Destroy 100 green spaceships
Finish your track
Destroy 50 red spaceships
Destroy 50 green spaceships
Destroy 25 orange spaceships
Destroy 50 orange spaceships
Finish 5 of your tracks
Finish 10 of your tracks