The paper reports about TerraSAR-X/TanDEM-X Bi-Directional (BiDi) short-term time series experiments. The TerraSAR-X and TanDEM-X satellites flew during the pursuit commissioning phase with an along track separation of 20 km and time series of up to 6 SAR images with repetition intervals of 1 s to 2.5 s were acquired. From the SAR images a sequence of up to 3 interferograms was generated with a repetition interval of 3.6 s. An acquisition constellation with interleaved BiDi and boresight acquisitions is described which allows for 3 repeated acquisitions by one satellite only. The Doppler spectrum is discussed and short-term time series of SAR images and interferograms are presented from acquisitions over Singapore and the Upsala Glacier in Argentina.