My wish is that the reader enjoys this dissertation and that it brings him/her a better understanding on Gas-Surface Interaction (GSI) phenomena. Nonetheless, this journey through the VKI doctoral program has been long, and I wouldn't be able to address this topic without acknowledging people that were by my side during this research, because without them this thesis would not have been possible: A big thank to Olivier Chazot for giving me the opportunity to develop my thesis in the Plasmatron facility. His office was always open and ready for discussion. A special mention to his telephone, most of the time ringing during each one of our conversations. Also to Roberto Flores, director of this thesis in UPC, who allowed me to keep in contact with my university. Following the experimental nature of this dissertation, I would like to mention also the contribution made by Pascal Collin. He did an excelent job running the Plasmatron and installing the probes. I will always remember his desperation when water leaks appear when making the vacuum in the chamber. I thank also the rest of the Plasmatron team: Bernd Helber and Damien Le Quang as radiation experts, and Işil Şakraker as advisor for calorimetric measurements. Many CFD simulations appear in this dissertaion. For that, the advice of Vincent Van Der Haegen, my office mate, has been extremely useful to achieve a converged solution. Also, the flight extrapolation technique developed here deserves my gratitude to Fabio Pinna, whose expertise in CFD helped me to improve my IXV simulations and achieve the "Pinna Certification". I really enjoyed working with them. Other VKI colleagues I want to mention are Alessandro Turchi, who helped me understand many aspects of GSI phenomena, Francesco Panerai who set the basis to develop this dissertation, and Georgios Bellas-Chatzigeordis to whom I encourage to continue with the catalytic model development and implementation in VKI numerical tools. Last but not least, special thanks to my family. They encouraged me to pursue a doctorate degree and supported me in the most difficult moments.