In-flight antenna characterization of a SAR instrument operating in complex TOPS mode

The antenna model used for correcting the influence of the antenna pattern on synthetic aperture radar (SAR) images requires on-ground validation and in-flight verification. A methodology based on the in-flight measurement of azimuth patterns with ground receivers has been successfully performed for the missions TerraSAR-X (TSX) and TanDEM-X (TDX), namely for operational modes and beams. Future satellite missions such as Sentinel-1 will have the novel and complex TOPS (Terrain Observation by Progressive Scans) as operational mode. This paper presents the first in-flight antenna characterization of a SAR instrument in TOPS mode with ground receivers, performed with experimental TSX data. The results demonstrate the suitability of the calibration approach and, extendedly, the accuracy and stability of the TSX antenna model.