Bistatic SAR for urban environments - Annual report 2009

The report summarises activities and results during 2009 for the research project "Bistatic SAR for urban environments". The objective of the project is to improve capabilities of future ground surveillance systems, in particular detection of concealed targets in difficult clutter environments. The project goal is to develop and evaluate the performance of airborne bistatic synthetic aperture radar (SAR) operating in the VHF and UHF bands. Studied scenarios include both urban and forest-covered terrain where bistatic SAR has shown promising results based on simulations. The project involves two international collaborations, i.e. a bilateral research collaboration with France and a multilateral collaboration with industries in France, United Kingdom and Sweden. A significant effort during the year has been preparations for the first bistatic flight tests together with France, which are planned to be conducted during weeks 50-51 in 2009. Analysis of synchronisation tests have shown that the GPS-method developed for frequency tuning provides sufficient accuracy for data recording. However, the residual phase drift between the systems needs to be estimated from radar data. Simulations have been conducted and an experiment plan has been defined. The project is also involved in SIMCLAIRS ("Studies for Integrated Multifunction Compact Lightweight Airborne Radars and Systems") which is conduced by a European industrial consortium and coordinated by the European Defence Agency (EDA). During the fall, FOI has had the responsibility to verify a prototype for a miniature CARABAS system aimed for helicopter installation which has been developed by Saab Microwave Systems. The results from the first set of measurements indicate that the radar electronics works well but that revision is required to eliminate internally generated interference signals. A new method for target detection has been studied during the year which is based on training data to optimise detection performance. The algorithm has been applied to SAR data from FOI's LORA system. Target signatures are computed from electromagnetic simulations whereas clutter signatures are estimated from collected radar data. The results are promising and indicate that smaller objects, e.g. small aircraft, concealed in forest may be detected with fewer false alarms than before.