The Data Innovation and Science Cluster (DISC) is a core element of ESA's data quality strategy for the Aeolus mission, which was launched in August 2018. Aeolus provides for the first-time global observations of vertical profiles of horizontal wind information by using the first Doppler wind lidar in space. The Aeolus DISC is responsible for monitoring and improving the quality of the Aeolus aerosol and wind products, for the upgrade of the operational processors as well as for impact studies and support of data usage. It has been responsible for multiple significant processor upgrades which reduced the systematic error of the Aeolus observations drastically. Only due to the efforts of the Aeolus DISC team members prior to and after launch, the systematic error of the Aeolus wind products could be reduced to a global average below 1 m/s which was an important pre-requisite for making the data available to the public in May 2020 and for its use in operational weather prediction. In 2020, the reprocessing of earlier acquired Aeolus data, another important task of the Aeolus DISC, also started. In this way, also observations from June to December 2019 with significantly better quality could be made available to the public, and more data will follow this and next year. Without the thorough preparations and close collaboration between ESA and the Aeolus DISC over the past decade, many of these achievements would not have been possible.

We highlight some of the scientific benefits of the Aeolus Doppler Wind Lidar mission since its launch in August 2018. Its scientific objectives are to improve weather forecasts and to advance the understanding of atmospheric dynamics and its interaction with the atmospheric energy and water cycle. A number of meteorological and science institutes across the world are starting to demonstrate that the Aeolus mission objectives are being met. Its wind product is being operationally assimilated by four Numerical Weather Prediction (NWP) centres, thanks to demonstrated useful positive impact on NWP analyses and forecasts. Applications of its atmospheric optical properties product have been found, e.g., in the detection and tracking of smoke from the extreme Australian wildfires of 2020 and in atmospheric composition data assimilation. The winds are finding novel applications in atmospheric dynamics research, such as tropical phenomena (Quasi-Biennial Oscillation disruption events), detection of atmospheric gravity waves, and in the smoke generated vortex associated with the Australian wildfires. It has been applied in the assessment of other types of satellite derived wind information such as atmospheric motions vectors. Aeolus is already successful with hopefully more to come.

The unique European Space Agency (ESA) Earth Explorer Aeolus Doppler Wind Lidar (DWL) is a success with beneficial impacts in weather and climate. At the IGARSS ‘21 venue we will share our results internationally and present initial studies that look into an operational Aeolus follow-on mission and describe lessons learned on the instrument, data processing and application of the winds. The ESA Aeolus mission now demonstrates the unique benefits of direct measurements of the atmospheric wind fieldon atmospheric dynamical analyses and forecasts. The many lessons learned from the Aeolus instrument development, its operation and data processing development are being exploited to help develop the requirements and design of an Aeolus follow-on mission in order to further enhance its application benefit globally. An overview of preliminary Aeolus and future DWL requirements will be presented to initiate a discussion with the international community gathered at IGARSS ‘21.

The European Space Agency's (ESA) wind mission, Aeolus, hosts the first space-based Doppler Wind Lidar (DWL) world-wide. Its scientific objectives are to improve weather forecasts and to advance the understanding of atmospheric dynamics and its interaction with the atmospheric energy and water cycle. The primary data product is profiles of horizontally projected line-of-sight winds from the surface up to about 30 km, and spin-off products are profiles of cloud and aerosol optical properties. Aeolus was launched on 22 August 2018, and the Atmospheric LAser Doppler INstrument (ALADIN) switch-on was completed with first high energy output in wind mode on 4 September 2018. The on-ground data processing facility worked excellent, allowing L2 product output in near-real-time (within 3 hours of sensing) from the start of the mission. During the first 20 months in orbit, ESA, the Aeolus Data Innovation and Science Cluster (DISC), Aeolus calibration and validation (CAL/VAL) teams and industry worked on the instrument commissioning, calibration, validation and product improvements, leading to the public release of the Level 2B (L2B) wind product in May 2020. The Aeolus L2B wind data were then of such good quality that four weather centers started to use the product in their daily forecasts during 2020, and more have plans to follow in 2021. As of May 2020, the biases of the near-real-time data were on average close to the mission requirements, although the random errors were higher than expected due to lower than expected atmospheric return signal on orbit. Other issues encountered in-flight were for example drifts in the instrument alignment and nonoptimal telescope focus and temperature control, leading to drifts in the laser emitted output energy and/or internal and atmospheric path signal strength and long term evolutions on the wind product bias. A further issue encountered was a gradually increasing number of “hot pixels”, i.e. pixels with elevated background signals, appearing on the ALADIN ACCDs over time. Mitigation strategies for these issues arebeing implemented, or are considered for a potential follow-on mission. The Aeolus optical properties spin-off product (L2A) has been further improved after launch, including methods for improved aerosol and cloud backscatter discrimination. The product has been used to study smoke emissions, e.g. from the early 2020 Australian fires, and has been successfully experimentally assimilated in Copernicus Atmosphere Monitoring Service (CAMS) model C-IFS. After two and a half years in orbit, and despite of some performance issues related to the ALADIN instrument, Aeolus has already achieved most of its scientific objectives. Finally, the mission was recently extended until end 2022.

This paper describes the current status of instrument predevelopment activities that are being performed in the frame of a potential Aeolus Follow-On mission (Aeolus-2). The main inputs for a future Doppler Wind Lidar (DWL) instrument that have been used are: lessons learned from the Aeolus development phases and the in-orbit operations and performance; initial inputs from EUMETSAT including an overall mission lifetime of 10–15 years utilizing 2–3 spacecraft (implying a lifetime of 5 years or more for each) with a launch of the first satellite in 2029, increased robustness and operability of the instrument, and an emphasis on reduction of recurrent costs; the maximum utilization of the demonstrated design heritage; and a number of recommendations for the requirements of a future DWL mission from the Aeolus Scientific Advisory Group (ASAG). These inputs have been collated and combined into a set of preliminary system requirements which have been used as the basis for a dedicated Instrument Consolidation Study. In addition, three instrument subsystem pre-development activities have been kicked-off: two laser transmitter pre-developments and the predevelopment of an improved detector. These developments have the aim to demonstrate that issues identified from the above are resolved and that the technology levels are sufficiently mature for the follow-on DWL mission.

ESA deployed the first Doppler Wind lidar in space within its Earth Explorer Mission Aeolus. The objective of Aeolus is to provide tropospheric and lower stratospheric wind profiles globally for the improvement of weather forecasts on short and medium term. Spin-off products are profiles of atmospheric backscatter and extinction coefficients and lidar ratio that can input for air quality models. After the successful launch in late August 2018 and following commissioning phase, the Calibration and Validation phase started in Decemeber 2018. The talk will recap the highlights of these phases and present the status of the mission.

ESA is launching a Doppler Wind lidar mission within its Earth Explorer Program. The objective of Aeolus is to provide tropospheric and lower stratospheric wind profiles globally for the improvement of weather forecasts on short and medium term. Spin-off products are profiles of atmospheric backscatter and extinctions coefficients and lidar ratio. The observations will also be used as input to air quality models and to verify climate model parameterization and predictability. In this way, Aeolus data is expected to greatly contribute to weather and air quality monitoring and to scientific advances in atmospheric dynamics. The Aeolus Mission is also a technology demonstrator, demonstrating the potential of an operational space-based Doppler Wind Lidar. After a long development and test phase the Aeolus mission is now gearing up for launch in Q3 of 2018.

ESA is launching a Doppler Wind lidar mission within its Earth Explorer Program. The objective of ADM-Aeolus is to provide tropospheric and lower stratospheric wind profiles globally for the improvement of weather forecasts on short and medium term. Spin-off products are profiles of atmospheric backscatter and extinctions coefficients and lidar ratio. The observations will also be used as input to air quality models and to verify climate model parameterization and predictability. In this way, ADM-Aeolus data is expected to greatly contribute to weather and air quality monitoring and to scientific advances in atmospheric dynamics. The Aeolus Mission is also a technology demonstrator, demonstrating the potential of an operational space-based Doppler Wind Lidar. After a long development phase the ADM-Aeolus mission is now gearing up for the last satellite level tests, preparing the mission for launch at the end of 2017.

The European Space Agency's (ESA's) Living Planet Programme includes two types of complementary user driven missions: the research oriented Earth Explorer missions and the operational service oriented Earth Watch missions. Earth Explorer missions are also divided into the Core missions being larger missions demonstrating the capabilities of new technologies addressing issues of wide scientific interest, and the Opportunity missions with a similar scope but being smaller in terms of cost. Within ESA's Living Planet Program, four lidar missions have been candidates, whereof two are selected and are being implemented. ESA's first lidar mission, the Atmospheric Dynamics Mission (ADM-Aeolus), was chosen as the second Earth Explorer Core mission in 1999. It shall demonstrate the potential of high spectral resolution Doppler Wind Lidars for operational measurements of wind profiles and their use in Numerical Weather Prediction (NWP). Additional Spin-off products are profiles of cloud and aerosol optical properties. The second mission hosting a Lidar, EarthCARE, was selected as the third Earth Explorer Core mission in 2004. It is a joint European and Japanese effort and targets radiation/cloud/aerosol interactions and processes. The EarthCARE high-spectral resolution lidar, ATLID, shall measure cloud and aerosol optical properties. Global measurements of these parameters are also of great importance to NWP and climate modeling. Furthermore DIAL concepts for CH4, H2O and CO2monitoring were candidates for ESA's 5th and 7th Earth Explorers. The missions were not selected, but initiated technology activities to raise the related technology levels [1,2].

The 'Living Planet Programme' of the European Space Agency (ESA) is gaining momentum. Six Earth Explorer missions are currently being implemented including ADM- Aeolus, ESA's Doppler Wind Lidar (DWL) mission. The Aeolus mission will demonstrate the capability of a space- borne high spectral resolution DWL to accurately measure wind profiles in the troposphere and the lower stratosphere (0- 30 km). The Mission thus addresses one of the main identified deficiencies of the current Global Observing System (GOS). From the backscattered frequency-shifted laser light it will be possible to obtain about 3,000 globally distributed horizontal line-of-sight (HLOS) wind profiles daily. The accuracy of the Aeolus winds, in cloud-free regions and above thick clouds, is expected to be comparable to that of radiosonde wind measurements. Additional geophysical products that will be retrieved from the Aeolus measurements are cloud and aerosol optical properties. Aeolus HLOS wind profiles will find wide application in Numerical Weather Prediction (NWP) and climate studies, improving the accuracy of numerical weather forecasting, advancing our understanding of tropical dynamics and processes relevant to climate variability and climate modelling. Impact experiments, assimilating synthetic Aeolus wind data into operational NWP models, have already been performed. One focus has been the forecast performance in regions known to be particularly sensitive to the accuracy of the initial conditions. The tentative results show that the largest benefits from Aeolus HLOS winds can be expected over the oceans and in the Tropics. In view of other lidar missions in space, the potential of a long-term database of cloud and aerosol optical properties is being studied. An additional topic is the potential benefit of wind profile observations in the lower stratosphere. Ground-based and airborne campaigns are being prepared for the validation of the Aeolus Airborne Demonstrator (A2D) - a high spectral resolution DWL instrument with technology very similar to Aeolus. This paper provides an overview of the Aeolus mission, the science and application activities being performed in support of the mission and the potential benefit of such observations in a wider context.