Detection of slow and fast moving targets using hybrid CD-DMTF SAR GMTI mode

TerraSAR-X and TanDEM-X has since 2014 been flying in the monostatic pursuit mode. This mode consists of a formation flying with the satellites having identic orbit, but with a displacement in along-track of a distance corresponding to 10 s delay. Such formation gives e.g. the ability to detect movements of very slow targets or targets standing still and moving between measurements. Depending on the integration time for each satellite and the time separation between the satellites, the clutter may behave as stationary or non-stationary. This allows for the possibility to apply either coherent or incoherent change detection algorithms. As has been proved earlier, the potential of coherent change detection has very good abilities but has proven difficult to obtain on X-band. In the case of very high resolution SAR, there will also be a target smearing effect due to the target movement within the coherent processing interval (CPI). The target defocusing effect may also be used for detection of moving targets in the scene using the so-called Detection of Moving Targets by Focusing (DMTF) technique. This is since an estimate or hypothesis test for target movements can be used to reprocess the SAR image and obtain a Signal-To-Clutter-Noise (SCNR) gain, thus increase chances for moving target detection. Therefore, a combination of DMTF and change detection over short times is promising. As such, this paper investigates the potential of the monostatic pursuit mode for GMTI.