Satellite Navigation

"A navigation system, usually referred to as ‘Attitude and Orbit Control’ is essential for the spacecraft to maintain its attitude, so that it can be directed towards its intended destination. This capability is also required to keep its solar panels pointed towards the Sun and its instruments pointing at specific targets. Attitude control is achieved with electronic 'eyes' (sun and star sensors). These can sense the location of the Sun and track the stars allowing the spacecraft’s position and orientation to be calculated. A propulsion system or reaction wheels controlled by appropriate software ensure then that the spacecraft is moved or oriented appropriately." (ESA, 2013)