The Rover's Robotic arm has 3 joints, corresponding to shoulder, elbow and wrist joints. There are 2 motors controlling the shoulder joint (for extra strength and stability) and a single motor each controlling the elbow and wrist joints. Sensors for the scientific instruments are mounted at the end of the 'wrist joint'. For safety reasons, the Robotic Arm's deployment has been preprogrammed, and each joint will only move in the horizontal plane (see video).
Watch a video from 'How it's Made' about building a robotic arm.
The Robotic Arm allows the Scientific Instruments mounted on the end of the arm to be placed directly up against rock and soil samples. The Robotic Arm can only be deployed if the Rover is stopped. The Robotics Engineer is responsible for the safe deployment of the Robotic Arm.
Photo right: Close-up of Robotic Arm sensors