Autonomous Magnetic Navigation for Earth Orbiting Spacecraft

The strength and orientation of the Earth's magnetic field varies as a function of the location of the observations, which means that the magnetic field measurements contains position information. Many artificial satellites carry a magnetometer on-board. The local magnetic field measurements could be used to provide navigation information. Such a navigation method has the advantage of requiring only data from low cost on-board instruments and has applications in low budget operation of satellite systems. Furthermore if processing can be performed on-board, this method leads to the possibility of fully autonomous long term navigation. In many systems magnetic navigation could be an effective back-up. To study the feasibility and potential performance of spacecraft magnetic navigation, the concept was investigated using two possible approaches. In a first configuration the magnetic field orientation is assumed to be complemented by measurements of the Nadir direction provided by an Earth horizon sensor on board; the two vectors form the basis of a "space sextant." In the second configuration magnetic field magnitude is the sole source of external information.