After solving the death of Travis (Depression Achievement) rejoin and continue following the tracks until you come to stationary metal freight containers. Turn left and climb the hill overlooking the containers and turn back towards the woods. Use
to zoom and look for four lights amongst the trees ahead which can be tricky to spot. Once you locate the lights go over to them and press them in a specific order to turn them blue. For me, it was 3-2-4-1 but it appears to be completely random. After you've turned all panels blue a spaceman will appear and you will need to follow him for a while until you reach a spaceship where you will be teleported to space. At the conclusion of your experience, a panel will open and a note will appear. Pick up the note and accept it to unlock the achievement.