**6. Acknowledgment**

I wish to acknowledge insights and valuable discussions with Prof. Fabio Rocca, Prof. Andrea Monti Guarnieri, and eng. Mauro Mariotti d'Alessandro at Politecnico di Milano. I also wish to thank to Dr. Malcom Davidson (ESA), Dr. Irena Hajnsek (DLR), Dr. Kostas Papathanassiou (DLR), Dr. Fabrizio Lombardini (Universitè di Pisa), Prof. Lars Ulander (FOI), Dr. Pascale Dubois-Fernandez (ONERA), Dr. Thuy Le Toan (CESBIO) with whom I have discussed many of the results within this chapter.
