1. ONERA, The French Aerospace Laboratory BP. 72, F-92322 Chatillon Cedex, France
2. Aix Marseille Univ., CNRS, CNES LAM, 38 rue F. Joliot-Curie, F-13388 Marseille, France
3. Centre for Advanced Instrumentation (CfAI), Durham University, South Road, Durham DH1 3LE, UK