Ground testing of the PHI Image Stabilisation System (ISS) for Solar Orbiter The Photospheric and Helioseismic Imager (PHI) on board of the ESA mission Solar Orbiter, to be launched in 2017, will provide measurements with high polarimetric accuracy of the photospheric solar magnetic field at high solar latitudes. The required pointing precision is achieved by an image stabilisation system (ISS) that compensates for spacecraft jitter. The ISS consists of a high-speed correlation tracker camera (CTC) and a fast steerable tip-tilt mirror operated in closed loop. This poster will present the test setup being used to demonstrate that the performance of the ISS is according to the requirements, and the results of these tests. The tests are performed with an extended light source representing the solar surface and a steerable mirror to simulate spacecraft jitter. With this setup the photometric characteristics of the correlation tracker camera and the electromechanical characteristics of the tip-tilt drive and tip-tilt controller are determined, as well as the performance of the whole ISS in closed loop mode.