Attitude & Orbit Control Systems (AOCS) are used to achieve and hold the geometrical objectives of satellites. The attitude of a satellite is important for pointing of payloads on-board and ensuring safety of the system. The orbit is key to fullfilling any satellite mission. Systems that are used for attitude and orbit control are e.g. Star Trackers, Sun Sensors and Gyroscopes for sensing the attitude, and thrusters, and reaction wheels as actuators. The control of these hardware components and the mission objectves is essential and typically consists of delicate and complex algorithms on robust computer systems. Dutch Space designed, produced and tested the Attitude & Orbit Control Systems for the scientific satellites ISO (an infra-red measuring satellite) and SAX (an x-ray measuring satellite). For current and future scientific missions, extraordinary pointing accuracies and stationing stabilities are required. Currently, the attitude & orbit control system for the joint Herschel-Planck mission is under development at Dutch Space.