Long-Term System Monitoring of Radiometric Stability – Current Status of TerraSAR-X and TanDEM-X

The TerraSAR-X and the TanDEM-X satellite produce high quality SAR images for a number of scientific and commercial applications. To guarantee the stability of the high accurate SAR products both systems are permanently monitored. The intention of this paper is to present the latest results of Long-Term System Monitoring (LTSM) in order to demonstrate the remarkable performance of both systems since launch. The study extends previous evaluations and updates their results. The evaluations focus on the three major indicators for monitoring the radiometric accuracy and stability of the SAR systems: - the radiometric properties of all T/R modules, i.e. the monitoring of gain and phase which are recorded within the SAR instrument and used for internal calibration, - the antenna pattern stability and deviations to the antenna model obtained from acquisitions over the Amazon rainforest – known as widely, uniformly distributed backscattering area, and - radiometric accuracy and stability of the SAR instrument derived from permanently mounted point targets, including integrated and peak-to-sidelobe ratio. For the latter a monitoring area with four corner reflectors was established and has been operated by the Institute near Neustrelitz since the beginning of TerraSAR-X operational phase in 2008 which will ensure a reliable monitoring of both SAR systems over the entire life time