20 Nov 2020

20 Nov 2020

Review status: a revised version of this preprint is currently under review for the journal AMT.

Characterization of dark current signal measurements of the ACCDs used on-board the Aeolus satellite

Fabian Weiler1, Thomas Kanitz2, Denny Wernham2, Michael Rennie3, Dorit Huber4, Marc Schillinger5, Olivier Saint-Pe5, Ray Bell6, Tommaso Parrinello7, and Oliver Reitebuch1 Fabian Weiler et al.
  • 1Deutsches Zentrum für Luft- und Raumfahrt, Institut für Physik der Atmosphäre, Oberpfaffenhofen, Germany
  • 2European Space Agency-ESTEC, Keplerlaan 1, Noordwijk NL-2201 AZ, The Netherlands
  • 3European Centre for Medium-Range Weather Forecasts, Shinfield Park, Reading RG2 9AX, United Kingdom
  • 4DoRIT, 82239 Alling, Germany
  • 5Airbus Defence and Space (Toulouse), Rue de Cosmonautes, 31400 Toulouse, France
  • 6Teledyne e2v, 106 Waterhouse Lane, Chelmsford Essex CM1 2QU, United Kingdom
  • 7European Space Agency-ESRIN, Largo Galileo Galilei 1, 00044 Frascati RM, Italy

Abstract. Already 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 4 m/s. This paper provides a detailed characterization of the hot pixels which occurred during the first one and a half 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 the 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 has almost linearly increased during the observing period between 2018-09-02 until 2020-05-20 with 6 % of the ACCD pixels affected in total at the end of the period leading to 9.5 % at the end of 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 inflight 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.

Fabian Weiler et al.

Status: final response (author comments only)
Status: final response (author comments only)
AC: Author comment | RC: Referee comment | SC: Short comment | EC: Editor comment

Fabian Weiler et al.

Fabian Weiler et al.


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Short summary
This paper reports on dark current signals anomalies of the detectors used on-board ESA's Earth Explorer Satellite Aeolus during the first one and a half years in orbit. After introducing sophisticated algorithms to classify dark current anomalies according to their characteristics, the impact of the different kinds of anomalies on the wind measurements is discussed. In addition, mitigation approaches for the wind retrieval are presented and potential root causes are discussed.