Contributions from the DISC to accomplish the Aeolus mission objectives

The Aeolus Data Innovation and Science Cluster (DISC) supports the Aeolus mission with a wide range of activities from instrument and product quality monitoring over retrieval algorithm improvements to numerical weather prediction (NWP) impact assessments for wind and aerosols. The Aeolus DISC provides support to ESA, Cal/Val teams, numerical weather prediction (NWP) centers, and scientific users for instrument special operations and calibration, for the re-processing of Aeolus products from the past and through the provision of bi-annual updates of the L1A, L1B, L2A and L2B operational processors. The Aeolus DISC is coordinated by DLR with partners from ECMWF, KNMI, Météo-France, TROPOS, DoRIT, ABB, s&t, serco, OLA, Physics Solutions, IB Reissig and Les Myriades involving more than 40 scientists and engineers. The presentation will highlight the Aeolus DISC activities with a focus for the year 2021 and early 2022 since the last Aeolus workshop in November 2020. This covers the evolution of the instrument performance including investigations of the cause of the on-going signal loss and the achieved improvement via dedicated laser tests in 2021. In addition, refinements of algorithms and correction of the wind bias will be discussed - including a known remaining seasonal bias in October and March as encountered during the re-processing campaigns. Finally, the strategy for the on-going and future re-processing campaigns will be addressed to inform the scientific community about the availability and quality of the re-processed data products. The Aeolus mission has fully achieved its mission objectives including the unprecedented demonstration of direct-detection Doppler wind lidar technology and high-power laser operation in space in the ultraviolet spectral region over its planned full mission lifetime of 3 years and 3 months. Aeolus wind products have clearly demonstrated positive impact on forecasts using several NWP models. Since early 2020, and thus only 1.5 years after launch, the Aeolus wind products are used in operation at various NWP centers worldwide. This was achieved even despite the larger than expected wind random errors due to lower initial atmospheric signal levels and the observed signal losses during the operation of the first and second laser. In addition to this incredible success, first scientific studies demonstrated the use of Aeolus for atmospheric dynamics research in the stratosphere and for the analysis of aerosol transport. These achievements of the Aeolus mission and its success were only possible with the essential and critical contributions from the Aeolus DISC. This demonstrates the need and potential for setting up such scientific consortia covering a wide range of expertise from instrument, processors, and scientific use of products for Earth Explorer type missions. The invaluable experience gained by the Aeolus DISC during the more then 3 years of Aeolus mission in orbit (preceded by a period of 20 years before launch by a similar study team) is a pre-requisite for a successful preparation of an operational follow-on Aeolus-2 mission

Assessment of the Aeolus performance and bias correction - results from the Aeolus DISC

Already within the first weeks after the launch of ESA's Earth Explorer mission Aeolus on 22 August 2018, the spaceborne wind lidar ALADIN (Atmospheric LAser Doppler INstrument) provided atmospheric backscatter measurements on 5 September and wind profiles on 12 September 2018. This swift availability of observations from ALADIN after launch is considered as a great success for ESA, space industry and algorithm and processor developer teams. These teams from scientific institutes, numerical weather prediction (NWP) centres, companies and ESA continuously improved and tested the retrieval algorithms and processors using sophisticated end-to-end simulation tools and experience gained with the airborne demonstrator for Aeolus for more than 15 years before launch. This cooperation from the pre-launch phase of Aeolus was extended within a new framework for exploitation activities of Earth Explorer missions named Data Innovation and Science Cluster (DISC) starting in January 2019. The Aeolus DISC activities range from instrument monitoring including calibration to algorithm refinement resulting in updates of the complete processor chain for all product levels every 6 months. DISC teams perform continuous monitoring of the product quality and provide regular reports in supports of external validation teams and ESA. Finally, wind product monitoring and impact experiments with NWP models are building an essential activity within the Aeolus DISC in order to achieve the objective of the Aeolus mission. In order to cover the broad range of activities, a multi-disciplinary team of experts, institutes and companies was established for the Aeolus DISC coordinated by DLR with ECMWF, KNMI, CNRS/Météo-France, DoRIT, ABB, S&T and Serco. During the presentation the Aeolus instrument performance for wind products, the discovered causes of the systematic errors and their correction will be discussed. Main achievements in this area are related to the characterization and correction of enhanced dark signal levels for single "hot" pixels in June 2019, the identification of the harmonic error contribution caused by the varying telescope primary mirror temperature variation in September- October 2019, the error in the on-board computation of the satellite induced Doppler frequency shift, and finally the observed temporal drift of a constant bias caused by drifts in the internal reference path. An outlook to the implementation of these corrections for real-time and reprocessed data products will be given

Contributions from the DISC to the Aeolus Mission in 2022 and 2023

The Aeolus Data Innovation and Science Cluster (DISC) supports the Aeolus mission with a wide range of activities from instrument and product quality monitoring over retrieval algorithm improvements to numerical weather prediction (NWP) impact assessments for wind and aerosol forecasts. The Aeolus DISC provides support to ESA, Cal/Val teams, numerical weather prediction (NWP) centers, and scientific users for instrument special operations and calibration, for the re-processing of Aeolus products and through the provision of bi-annual updates of the L1A, L1B, L2A and L2B operational processors. The Aeolus DISC is coordinated by DLR with partners from ECMWF, KNMI, Météo-France, TROPOS, DoRIT, ABB, s&t, serco, OLA, Physics Solutions, IB Reissig and Les Myriades involving more than 40 scientists and engineers. The presentation will highlight the Aeolus DISC activities with a focus for the year 2022 and early 2023 since the last Aeolus workshop in Taormina, Italy during April 2022. This covers the evolution of the instrument performance including the significantly enhanced performance wrt. signal levels and random errors since the switch back to the flight model FM-A laser in October-November 2022. In addition, refinements of algorithms and processor updates will be outlined, which were introduced for the baseline B15 (13 September 2022) and B16 (expected to be released in spring 2023). A summary of the quality for the 3rd re-processing campaign for initial FM-A data (September 2018 - June 2019) will be give and an outlook to the 4th re-processing campaign covering the complete Aeolus mission. An outlook will also introduce some of the planned instrument activities in summer 2023 at the end of the expected mission lifetime of Aeolus. The Aeolus mission has fully achieved its mission objectives including the unprecedented demonstration of direct-detection Doppler wind lidar technology and high-power laser operation in space in the ultraviolet spectral region for more than 4 ½ years up to now - exceeding the planned mission lifetime of 3 years and 3 months. Aeolus wind products have clearly demonstrated positive impact on forecasts using several NWP models. Since early 2020, and thus only 1.5 years after launch, the Aeolus wind products were used in operation at ECMWF and at various NWP centers worldwide. This incredible success of Aeolus paved the way for the decision taken by the member states of ESA in November 2022 on the way forward of an operational follow-on wind lidar mission. These achievements of the Aeolus mission and its success were only possible with the essential and critical contributions from the Aeolus DISC. This demonstrates the need and potential for setting up such scientific consortia covering a wide range of expertise from instrument, processors, and scientific use of products for Earth Explorer type missions. The invaluable experience gained by the Aeolus DISC during the more than 4 years of Aeolus mission in orbit (preceded by a period of 20 years before launch by a similar study team) is a pre-requisite for the successful preparation of an operational follow-on wind lidar mission planned within the EUMETSAT Polar System (EPS) program