Experts from the Ludwig Maximillian University in Munich (Dr. Volker Freudenthaler, Dr. Nikos Siomos) with the POLIS reference lidar are joining the specialists from Romania (Dr. Livio Belegante, Dr. Victor Nicolae, Drd. Razvan Pirloaga) with the RALI and ALPHA reference lidars in order to measure side-by-side and assess the performances of each of the systems. Moreover, experts from the University of Warsaw (Dr. Iwona Stachlewska, Afwan Haviz) will join the campaign starting 19 September with the European Space Agency's EMORAL reference system. Quality Assurance tests are performed before sunrise and at noon, weather permitting. The data is analysed in parallel by the experts (manual analysis) and with the automatic software newly developed at CARS. The goal is to optimize the automatic procedure for being further implemented at all lidar stations.