TerraSAR-X is a high resolution synthetic aperture radar (SAR) satellite launched in 2007. Its active phased array X-Band antenna hosts 384 transmit/receive modules (TRMs) controlling the beam steering in azimuth and eleva-tion. A calibration network provides monitoring of internal instrument behaviour by introducing additional calibration pulses. Evaluation of calibration pulses for every image acquisition guarantees high radiometric stability of all SAR products. This paper shows the latest in-orbit results of the radar instrument stability and TRM performance. The novel PN Gating method is verified in a spaceborne environment for the first time ever
