Proton-induced degradation of charge transfer efficiency on FLEX CCD detectors: measurement and impact on instrument performances

The exposure of Charge-Coupled Devices (CCD) to high-energy particles in space leads to a degradation of their performances. One of the observed mechanisms is the creation of defects in the CCD silicon lattice by displacement damage, inducing a reduction of the Charge Transfer Efficiency (CTE), i.e. the ability of the device to efficiently transfer the photo-induced charge to the read-out output node. Hence a reduction of the imaging quality of the detector. We present here a comparison of the modelled and measured optical quality of the FLEX CCD exposed to a high energy proton flux. The optical quality was directly measured on an irradiated flight representative device. A physical model of the detector, including an accurate modelling of the charge trapping dynamic, is used to generate synthetic scenes affected by CTE degradation from which the optical quality is assessed and compared to the measurement. Eventually the correlation of the model and the measurement will allow to accurately assess the performances of a detector exposed to space radiation environment.