Characterization of transient signal induced in IR detector array by Jupiter high-energy electrons and implications for JUICE/MAJIS operability

International audienceMAJIS is the visible-infrared spectral imager of the JUICE mission, scheduled by ESA to explore Jupiter and its three icy Galilean moons starting in 2030. It will encounter a challenging environment, the intense Jovian magnetosphere, which among the various expected effects of radiation on detector operability, raises the major issue of transient signal perturbations generated by electrons during every acquisition. This paper aims at a precise characterization of the consequences of such a flux of high-energy electrons on MAJIS detectors in order to evaluate their impact on their operability. To assess the effects of this environment on MAJIS during the mission, we exposed two candidate detectors for the mission to β- radioactive sources simulating an environment around the ~ MeV energy. The candidate detectors under tests were Teledyne H1RG and SOFRADIR Retina NGP MWIR with 5.3 μm cut-off. We have developped and validated an algorithm to interpret these measurements and characterize the distribution of electron impacts (or "spikes") both in terms of intensity and spatial distribution. The main trends we identify are that the Sofradir detector generates in average 1 spike per electron while the H1RG generates in average 2 spikes per electron forming a spatial cluster. The counterpart that we observe is that more energy is deposited in single spikes on the Sofradir than on the H1RG. Yet, the transient signals are of the order of magnitude of 1000 charges in average, filling less than 1% of the full-well capacity of both detectors. Since the foreseen strategy to discriminate the spikes is time filtering on acquisitions that will be split into sub-integrations, the absence of time persistence of the spike signal was paramount and we managed to check its absence on both detectors. We conclude that the expected effects on operability should be effectively mitigated by the foreseen despiking strategy