Here is the full list of all 15 Planet Assault achievements.
Congratulations you Completed the Tutorial!
Completed a Survival Level
Completed a Journey Level
Completed an Artillery Range Level
Congratulations you Completed your first Galaxy
Congratulations you Completed your Journey
You Survived till Level 10
You Survived till Level 20
You Survived till Level 30
You Survived till Level 40
You Survived till Level 50
You Scored 1500 Points in a Single Level
You Scored 2000 Points in a Single Level
You Scored 3500 Points in a Single Level
You Scored 5000 Points in a Single Level