Due to the COVID-19 pandemic, the GASS 2020 LOC and the URSI Board decided to cancel the organization of the 33rd URSI General Assembly and Scientific Symposium as a physical event. However the GASS 2020 LOC and the URSI Board also decided, in view of the record number of submitted papers and in order to value the work of all our fellow researchers, to publish the proceedings of the 33rd General Assembly and Scientific Symposium, available through the URSI website. Consequently, the GASS 2021 will be the 34th General Assembly and Scientific Symposium of our union.