Switchover to the Redundant SAR Instrument Chain on the TanDEM-X Satellite

Inhalt:
TanDEM-X (TDX-1) is a German radar satellite launched in 2010 which serves the TerraSAR-X and TanDEM-X missions together with its companion TerraSAR-X (TSX-1), launched in 2007. This paper describes the activities performed in July 2019 to switch TDX-1 from operationally using the nominal SAR instrument chain to the corresponding redundant unit. First, the steps from failure isolation until back again in operation are described. Necessary tests of the on-board functions which are preventing the mutual illumination between the two satellites flying in close formation are detailed and finally the first datatake acquired with the TDX-1 redundant instrument chain is shown.