Long-Term Monitoring of TerraSAR-X and TanDEM-X Ultra-Stable Oscillators

Inhalt:
The satellites TerraSAR-X and TanDEM-X are operated in close formation to acquire synthetic aperture radar (SAR) images for scientific and commercial applications as well as for global high precision digital elevation models (DEMs). In order to ensure the expected quality of those products and to monitor the performance and stability of the SAR instruments, a long-term system monitoring (LTSM) process has been established for critical system parameters and hardware elements. This paper focuses on the methodology of monitoring of the ultra-stable oscillators (USOs) on both satellites over the extended mission time, the events encountered and the measures that have been taken to restore nominal operations.