Aeolus and Aeolus-2 – ESA’s Doppler Wind Lidar developments for atmospheric dynamics and composition science and services

For more than two decades, the European Space Agency (ESA) has engaged in the development of Doppler wind lidars from space. The launch of the Aeolus Earth Explorer Mission on 22 August 2018 marked a major step in demonstrating the capabilities of space-borne Doppler wind lidars for advancing our understanding of atmospheric dynamics and composition for science and operational applications. During its almost 5 years in orbit Aeolus has providedunprecedented insights into global wind patterns and aerosol distribution, enhancing our ability to forecast weather, monitor climate change, and improve air quality. In addition, Aeolus has enabled key technical insights that paved the way for the development of the next generation of Doppler wind lidars demonstrating the technology and serving as an in-orbit testbed. Aeolus carried a single instrument, the Atmospheric Laser Doppler Instrument (ALADIN). This powerful lidar system used a 355 nm UV laser to emit pulses of light into the atmosphere, then measures the Doppler shift in the returned signal after it is scattered by molecules and particles in the air allowing the retrieval of atmospheric wind profiles and aerosol characteristics. The satellite operated in a Sun-synchronous orbit at an altitude of around 320 kilometers, enabling it to cover the entire globe. The Aeolus mission ended nominal operations on 30 April 2023, followed by the end-of-life phase where scientific and technological experiments were carried out before the satellite reentered from space on 28 July 2023 through an innovative and reentry approach.

Building on Aeolus’ success and lessons learned, in particular its clear positive impact on numerical weather forecasting,resulted in an interest for an operational Doppler wind lidar mission to serve meteorological centers and agencies in the 2030 to 2040 time frame. This resulted in a request by the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT) to ESA to carry out the necessary pre-developments activities for an operational Aeolus-2/eps-Aeolus mission to further enhance global wind measurements addressing the limitations encountered by Aeolus. Initial requirements from EUMETSAT include a mission lifetime more than 10 years utilizing two spacecraft with a launch of the first satellite in 2030s, increased robustness and operability of the instrument, and an emphasis on reduction of recurrent costs. In addition, the mission development shall maximize the utilization of the demonstrated design heritage and respond to recommendations from the ESA Aeolus and ESA/EUMETSAT DWL Scientific Advisory Groups

The paper will provide an overview of the main scientific achievements of the Aeolus mission, including the results from the international Cal/Val campaigns and the outcome of the end-of-life phase, as well as the current status of Aeolus-2 instrument pre-development activities.