Design and Radiation Hardness of Next Generation Solar UV Radiometers

For next space-based ultraviolet (UV) solar radiometers, we propose a design based on subsystem components that are selected according to lessons learned from previous flying missions and ground irradiation campaigns. UV interference filters inherited from space-based solar missions show strong degradation caused by structural changes that lead to an important decrease of visible light rejection. Wide bandgap semiconductors (WBGS) are used for the photodetectors: innovative metal-semiconductor-metal (MSM) based on Aluminum Nitride (AlN) and Diamond-based PIN photodetectors were developed, characterized and compared to the commonly used silicon photodiode technology (AXUV and SXUV types). Insignificant degradation of the WBGS based-photodetector performances were observed after exposure to protons of 14.4 MeV energy showing a good radiation tolerance up to fluences of 1x10^11 p+/cm2. Onboard calibration strategy based on UV LEDs are used as well to distinguish the detector's drift from inevitable degradations of the optical front filters.