Accomplish the indicated achievement to get the number of Xbox Live Gamerscore points.

Achievement	How to unlock
Alien Archivist ( 20 points )	Collected all Alien Captive Recordings.
Among the Stars ( 20 points )	Completed "Among the Stars".
Not of This World ( 20 points )	Completed "Not of This World".
This Galaxy Ain't Big Enough... ( 40 points )	Completed "This Galaxy Ain't Big Enough...".