In-Flight Hot Pixels and Random Telegraph Signal in Aeolus Accumulation CCDs Operated at Low Temperature

The European Space Agency’s (ESA) Aeolus mission utilized a space-based light detection and ranging (LiDAR) instrument for atmospheric wind measurements. These measurements were derived from signals collected by accumulation charge-coupled Devices (ACCDs), which showed unexpected behavior in flight. During the nearly five-year operation of the exploratory mission, hot pixels in the silicon detectors appeared at an almost-linear rate, most of which exhibited random telegraph signal (RTS) behavior, contrary to predictions based on pre-flight testing. The discrepancy highlights a gap between ground-based radiation tests, typically conducted at room temperature, and in-flight silicon detector conditions of low temperature and low readout noise levels. In-flight dark current activation energies and RTS phenomena observed in ACCD pixels are analysed, including suspected electric field enhancement (EFE) effects. This study compares these in-flight anomalies with literature models that forecast displacement damage dose (DDD)-induced dark current rates to determine if space radiation effects could be the primary cause of the hot pixels.