Investigations on TOPS interferometry with TerraSAR-X

This paper presents results on SAR interferometry with the so-called TOPSmode. The rationale to retrieve accurate interferometric products with such a mode is expounded, emphasizing the critical step of coregistering the pairs. Due to the particularities of the TOPS mode, a high Doppler-centroid is present at burst edges, demanding very high azimuth coregistration performance. A coregistration accuracy of one tenth of a pixel, as it is usually recommended with interferometric applications, will result in a large undesired azimuth phase ramp in the TOPS mode, above all at X-band. This paper presents two approaches based on the spectral diversity technique to estimate this offset with the required accuracy. Experimental results with repeat-pass TerraSAR-X data are shown to validate the proposed approach.