Investigations on the TOPSAR acquisition mode with TerraSAR-X

The paper reports about investigations on the implementation of the recently proposed TOPSAR acquisition mode with TerraSAR-X. Differently from ScanSAR,TOPSAR mode allows a wide swath coverage with nearly uniform signal to noise ratio (SNR), therefore avoiding scalloping and azimuth dependent SNR. To achieve this goal the antenna beam is steered within the different swaths in the along-track direction. TerraSAR-X can electronically steer the azimuth beam; however, angle quantization is introduced because of the limited number of available azimuth beams per data take. The effects of the TerraSAR-X angle quantization of the antenna steering are analyzed resulting in a negligible distortion. The maximum azimuth steering angle of TerraSAR-X allows the implementation of TOPSAR with the same coverage and resolution as the nominal TerraSAR-X ScanSAR mode, four range subswaths with 16 m azimuth resolution and a total swath of 100 km. Finally,TerraSAR-X TOPSAR interferometry capability and the possibility of using an inverse TOPSAR configuration are discussed.