Detector performance of the space-borne Doppler wind lidar aboard the Aeolus satellite

Abstract

The European Space Agency's Aeolus mission (2018-2023) was the first to provide global wind measurements in near-real time using spaceborne Doppler wind lidar. Its instrument, the Atmospheric Laser Doppler Instrument (ALADIN), significantly advanced weather forecasting and atmospheric research. A persistent challenge during the mission was the presence of hot pixels on ALADIN's CCD detectors, which caused dark current anomalies and compromised wind data quality. These effects, often observed as random telegraph signals (RTS) and abrupt shifts in median dark current levels, required rigorous correction strategies. To address these issues, up to eight dark current calibrations were performed daily, resulting in an extensive dataset used to identify, monitor, and statistically characterize hot pixel behavior throughout the mission. This study presents a comprehensive analysis of hot pixels, including new insights into the correlation between RTS transition rates and amplitudes, and between activation energies and dark current rates. These analyses not only improved the accuracy of Aeolus wind products during reprocessing but also deepened understanding of CCD detector behavior in space environments. Dedicated end-of-life tests in 2023 further clarified the temperature dependence of dark currents and the origins of hot pixels. The results have direct implications for future Doppler lidar missions such as EarthCARE and Aeolus-2, as well as for other satellite systems employing CCD-based sensors.