The TerraSAR-X and the TanDEM-X satellite are operated to enable two missions in parallel: the TerraSAR X and the TanDEM X mission for scientific and commercial applications providing a multitude of SAR products of high accuracy and reliability. After launch the whole SAR system of both satellites was successfully calibrated and verified during the commissioning phase: in 2007 for TerraSAR-X and in 2010 for TanDEM-X. In order to ensure a reliable and stable operation of both systems and to guaranty the excellent quality of their SAR data products, both systems have been constantly monitored since start of the operational phase. Based on previous evaluations, this paper presents the latest results of different Long-Term System Monitoring (LTSM) tasks and demonstrates the remarkable performance of both systems since launch.
Long term statistics over the mission lifetime are established by using the following system relevant parameters and instrument characteristics:
• Gain and phase stability of transmit/receiver modules (Internal Calibration)
• Temperature behavior of front end panels
• Differences between measured antenna patterns and reference patterns acquired over the Amazon rainforest (Relative Radiometric Calibration)
• Stability of the radar cross section, the integrated and the peak to side lope ratio of deployed reference targets (Absolute Radiometric calibration)
• Geometric resolution in azimuth and range direction
• Doppler centroid stability