Dr Didier Fussen (born on 28-Dec-1956), Head of Department Solar Radiations in Atmospheres, was the leader of the Limb Remote Sounding group at the Belgian Institute for Space Aeronomy (BISA). He joined this federal scientific institute in 1988 after a PhD degree in Atomic Physics at the "Université Catholique de Louvain" (UCL). He is presently the Principal Investigator of ALTIUS, an ESA EarthWatch mission on board a micro-satellite that will perform atmospheric limb imaging in the UV-VIS-NIR domain. He was also coordinating the PICASSO cubeSat mission and proposed its VISION spectral imager. He was a member of the Board of Directors and of the Scientific Council of the Belgian Institute for Space Aeronomy. He was also invited professor at UCL. After his retirement as a permanent member of BISA staff, he is half-time working in a research position mainly focused on the ALTIUS mission.