Space-based radar imaging

The technology for space-based imaging radar is not new but is currently attracting an increasing interest. The capabilities of the space-based radar systems have improved, e.g., with higher image resolution. The costs have also decreased, which enables more states to operate their own radar satellites. Not only nations such as USA, Russia and China, but also Italy and Israel, have operating radar satellites. The military use of space-based imaging radar includes surveillance over large areas and access to high-resolution images, although these two capabilities cannot be achieved simultaneously. Radar systems allow, in contrast to electro-optical systems, surveillance independent of light conditions and cloud coverage. The development of military systems are approaching a resolution at the decimeter level. Civilian systems have coarser resolution but may still be of interest for military intelligence gathering purposes. The highest resolution in civilian systems is of the order of one or a few meters, which is often a minimum requirement in military applications. Dual-use systems, with both military and civilian application, are rather common. A study of current and planned space-based radar systems have been undertaken within this project. Both the technical performance of the radar satellites and the satellite orbits have been of interest. The possibility of implementing radar systems on small satellites have been addressed. This report presents interesting trends in space-based radar imaging, with implications for radar performance. Typical and interesting orbits for radar satellites are also discussed. Some particularly interesting examples of radar satellites are mentioned.