I Admire its Purity (20)

Detect 30 targets with the motion tracker

You will receive the motion tracker in the beginning of the fourth mission, “Seegson Communications.”

You must detect 30 unique enemies for this achievement, you cannot keep tapping the RB and whip out the motion tracker 30 times on a single enemy.

As you progress through the game you’ll earn this achievement with no problems. Most people should unlock this naturally during missions six or seven.