26-GHz data downlink for LEO satellites

State-of-the art downlink technology allows Low Earth Orbit (LEO) satellites for Earth observation (EO) to downlink just above 500 Mb/s in the X-band due to bandwidth limitations. X-band is also becoming very congested. The ITU allocates four times more bandwidth in the 26 GHz band (i.e. 25.5 to 27 GHz) for the EO downlink. This 26 GHz band is particularly challenging in terms of atmospheric propagation effects. Data downlink (DDL) system studies, propagation characterization studies and pre-development of technology are on-going in Europe and in the USA. This paper addresses the main system architecture and related technical challenges. The existing data downlink infrastructure in the 26 GHz band is presented, and then the paper focuses on the programmatic approach both in Europe and in the USA in order to enable future missions to use the 26 GHz data downlink for LEO satellites with data rate capabilities above 1 Gbps by the end of this decade.