Abstract. Even just shortly after the successful launch of the
European Space Agency satellite Aeolus in August 2018, it turned out that
dark current signal anomalies of single pixels (so-called “hot pixels”) on
the accumulation charge-coupled devices (ACCDs) of the Aeolus detectors
detrimentally impact the quality of the aerosol and wind products,
potentially leading to wind errors of up to several meters per second. This paper provides
a detailed characterization of the hot pixels that occurred during the
first 1.5 years in orbit. The hot pixels are classified according
to their characteristics to discuss their impact on wind measurements.
Furthermore, mitigation approaches for the wind retrieval are presented and
potential root causes for hot pixel occurrence are discussed. The
analysis of the dark current signal anomalies reveals a large variety of
anomalies ranging from pixels with random telegraph signal (RTS)-like
characteristics to pixels with sporadic shifts in the median dark current
signal. Moreover, the results indicate that the number of hot pixels
almost linearly increased during the observing period between 2 September 2018
and 20 May 2020 with 6 % of the ACCD pixels affected in total at the end
of the period leading to 9.5 % at the end of the mission lifetime. This work
introduces dedicated instrument calibration modes and ground processors,
which allowed for a correction shortly after a hot pixel occurrence. The
achieved performance with this approach avoids risky adjustments to the
in-flight hardware operation. It is demonstrated that the success of the
correction scheme varies depending on the characteristics of each hot pixel
itself. With the herein presented categorization, it is shown that
multi-level RTS pixels with high fluctuation are the biggest challenge for
the hot pixel correction scheme. Despite a detailed analysis in this
framework, no conclusion could be drawn about the root cause of the hot
pixel issue.