Simulation of imaging effects of very high resolution SAR systems

Current space borne synthetic aperture radar (SAR) systems are able to provide users with high resolution image data of around one meter. Focusing on systems operating in the X-band, this value is not the end of possible improvements in resolution. There still lies a great potential in an increase of bandwidth of the radar signal itself and also in a significant enlargement of the synthetic aperture. From the technical point of view this certainly is a challenge, but could be possible for future space borne SAR missions already with current state of the art hardware. As a matter of proof TerraSAR-X introduces a new staring spotlight image product that significantly improves the azimuthal resolution to around a quarter of a meter. The technical realization of the very high resolution SAR system is not the only obstacle to overcome. Especially the increase of Doppler bandwidth along the synthetic aperture requests special treatment and considerations in system design from a signal processing's point of view. Challenges like orbital accuracy, tropospheric effects, approximations in SAR processing methods and depth-of-focus issues have to be addressed. In this paper, most of these challenges are studied separately by performing parametric simulations for single point targets and also for complex signatures of an airplane. A comparable SAR parameter set as used by the high resolution sliding spotlight mode and the new staring spotlight mode of TerraSAR-X are used for simulation.