GEOS-C will be the third of a series of spacecraft designed for the National Geodetic Satellite Programme. The two earlier and successful spacecraft were designated GEOS-I and II. In these, geocentric stabilisation was acheived to optimise the usage of the radiated and reflected radio and optical power of the geodetic observations. It was the atmospheric attenuation of the optical beacons, by which the spacecraft could be photographed against a star background, which imposed the accuracy requirement of earth pointing to within 5°. Descriptions as well as performance analyses of these attitude control systems have been published. In each, the proper mass distribution was obtained through an end mass on a de Havilland extendible boom. Since initial misorientation and perturbing torques induce motion about the equilibrium orientation in a gravity-gradient system, a mechanism for energy dissipation is necessary. A Magnetically Anchored Eddy Current Damper was used for this purpose. It consists of a magnet assembly that is free to lock onto the geomagnetic field and rotate freely within a conducting spherical shell. Relative motion of the two produces eddy currents in the conductor which in turn impede the relative motion.