ESA’s Wind Lidar Mission Aeolus – Instrument Performance and Stability

The European Space Agency, ESA deployed the first Doppler wind lidar in space within its Earth Explorer Mission Aeolus in August 2018. After the initial commissioning of the satellite and the single payload ALADIN, the mission has started to demonstrate the capability of Doppler lidar to measure wind from space. In order to provide the best Aeolus wind product possible, detailed monitoring of the instrument is crucial for analysis of system health, but also for the assessment of measurement performance and data product calibration. Within the last 1.2 years the different instrument modes to assess instrument and laser health, as well as the nominal wind processing indicated longterm instrument drifts. The laser beam profile has been monitored and showed an energy redistribution within the beam. The line of sight has slowly drifted, resulting in a change of incidence angle at spectrometer level. The impact of these observed drifts on the wind product are compensated on demand by updates of dedicated ground processing calibration files. This contribution will provide an overview about the Aeolus instrument modes and the observed stability that are needed to provide the Aeolus wind product. The current Aeolus performance has been assessed by various Numerical Weather Prediction centers. The positive outcome is represented by ECMWF’s decision to start using Aeolus data operationally on 9^th January 2020.