TerraSAR-X is a satellite mission for scientific and commercial applications providing a multitude of SAR prod-ucts of high accuracy and reliability. The instrument and SAR performance have been successfully verified in the commissioning phase and are monitored since start of the operational phase. This paper presents the results of the performance supervision over time, and confirms the stability of the excellent image quality delivered in the Ter-raSAR-X mission. It also describes the efforts to acquire images for the TerraSAR-X mission with the future TanDEM-X satellite and to preserve its excellent performance.