1. Process for identifying an incorrectly measuring sensor in a sensor arrangement on a spacecraft for measuring external directional vectors relative to a spacecraft-fixed system of coordinates, which directional vectors indicate directions of external objects with respect to an actual location of the spacecraft, or external field vectors at the actual location of the space craft, said process comprising: measuring respective external directional vectors with respect to a spacecraft-fixed system of coordinates based on signals from said sensor arrangement; calculating respective external directional vectors with respect to an inertial system of coordinates, based on information concerning an actual point in time and actual location of the spacecraft; determining angles between individual directional vectors measured by means of the sensor arrangement, and angles between calculated individual directional vectors; comparing angles which correspond to one another with respect to participating directional vectors from the two systems of coordinates; and identifying a particular sensor as measuring incorrectly if all angles determined based on a directional vector measured by the particular sensor deviate from one another by more than a definable minimum amount.