Complete each achievement to get the allotted gamerscore.

Unlockables

Exploring Jupiter (20) Make it to Jupiter.
Exploring Saturn (20) Make it to Saturn.
Exploring Uranus (10) Make it to Uranus.

Good Start (10) Get 12,000 points in the first stage.

Mars Attack (30) Make it to Mars.
Mother Earth (30) Make it to Earth.

Partnership (10) Obtain a score of 60,000 during an Xbox Live Co-op game.

Safety First (10) Make it to Neptune without losing a life.
Sharp Shooter (10) Kill all ships on the first 3 bonus levels.

Team Work (20) Obtain a score of 200,000 during an Xbox Live Co-op game.
Too Good (20) Win 50 Xbox Live Versus games.
Tough Guy (10) Make it to stage 7 without obtaining any bonus weapons.