In pR&D 2 (external sensors), the team assembled the AEV following the instructions found in the AEV documents. After the AEV was assembled, the reflectance sensors were attached on the arm by the wheel with silver markings. The reflectance sensors purpose is to gauge how far the AEV has moved along the track. One mark (the silver part of the wheel) is equal to .4875 inches. The reflectance sensors help determine when the AEV should stop or begin to slow down/speed up during the performance tests.