Interferometric Evaluation of Sentinel-1A TOPS data

Abstract

The European radar satellite Sentinel 1A was launched in April 2014 as the first of the Copernicus Space Component. The Sentinel 1 system has been conceived to provide repeat-pass interferometric capabilities with wide area coverage for medium resolution applications. Wide-swath is achieved by employing the novel TOPS (Terrain Observation by Progressive Scans) acquisition mode. The contribution of this talk focuses on an interferometric evaluation of Sentinel-1A data. A brief description of the interferometric algorithms of the Integrated Wide Area Processor at DLR is provided. The spectral properties of TOPS data are exposed and the stringent coregistration accuracy emphasized, where a pixelwise ESD-based estimator is proposed. Burst mode data require that repeat-pass acquisitions are synchronized in order to obtain coherence over distributed scatterers. An evaluation of the common Doppler bandwidth for two stack of S1A scenes is provided. By exploiting the high sensitivity of TOPS data to the measurement of the along-track shift, an assessment of the shifts is as well provided for two scenarios. In the first place a temporal analysis is done with two stacks of acquisitions in different acquisiton geometries. Geophysical effects as diferential solid Earth tides are compensated. The outcome of this analysis indicates that a mere geometric coregistration is not enough to obtain accurate interferometric results, being necessary to compensate for orbital timing errors. The second analysis focuses on the systematic evaluation of the along-track shifts for a datatake composed by several slices, where good spatial stability is shown.