This paper presents a numerical tool able to generate realistic SAR images from accurate vessel models for a given orbital sensor. Its capability to extract high resolution radar signatures converts this SAR simulator in a useful tool for vessel classification studies and, furthermore, to define a future constellation of SAR sensors bound for carry on an automatic vessel monitoring system. This SAR simulator has low computational requirements as it is based on high
frequency electromagnetic calculations making feasible to run it in a simple PC. In this paper, the main scheme of the simulator and its capability to consider the vessel velocity and the ocean waves, which can produce an important distorting effect in the final SAR images, will be presented as well as some validation results and particular aspects of vessel modeling. Finally, some examples of radar signatures of precise fishing vessel models are exposed.