The ESA Arctic Weather Satellite (AWS) Programme was approved at the ESA Council Meeting at Ministerial level in Seville, Spain in 2019. ESA initiated mission preparation activities with industry in early 2020 and these activities were concluded in late 2020. In February 2021 ESA kicked–off Phase B/C/D/E contract with OHB Sweden as the prime contractor, responsible of the development of the AWS Space Segment and Ground Segment. The OHB industrial team will also be responsible of the operations of the AWS prototype flight model (PFM) satellite. The launch of the AWS PFM satellite is planned in 2024.

The ESA AWS programme is conceived to develop the prototype and in-orbit demonstration satellite for a future constellation of AWS satellites providing all-weather microwave sounding of the global atmosphere with frequent revisit observations over the Arctic region. With the increased recognition of the significance of the polar regions with respect to climate change and the increased economic and research activities occurring in the Arctic, such observations have assumed an increased importance. AWS Constellation will be designed to complement the existing microwave sounders of MetOp-SG and NOAA satellites, improving nowcasting and NWP on a global scale. Consequently, the AWS constellation orbits will be selected to maximise the complementarity. The AWS constellation would provide humidity and temperature sounding data products with unprecedented revisit times and data timeliness. It is envisaged that such a future constellation would be implemented in cooperation with EUMETSAT.

The AWS prototype satellite is designed and qualified taking into account the AWS constellation requirements so that no design changes are foreseen from the PFM Satellite to the constellation Satellites (e.g. covering different orbital planes with different equatorial crossing times).

AWS instrument is a traditional cross-track scanning microwave radiometer, providing a total of 19 channels from 50 GHz up to 325 GHz. AWS provides humidity and temperature profiles and it will also contribute to precipitation measurements. Due to the lower orbit altitude (around 600km), the spatial resolution of the humidity sounding measurements will be improved compared to other operational sounders.

AWS provides two services to end-users. A Stored Mission Data (SMD), consists of one full orbit of data, and is downlinked to Ground station in Svalbard once per orbit and data is disseminated using EUMETSAT’s EUMETCast system. A Direct Data Broadcast (DDB) provides AWS real time data from the instrument. The DDB data is provided using L-band data downlink and the link is always ON allowing everyone with a ground station to downlink the data. Level1b processor will be made available to end users allowing to process the raw instrument data into Level1b product (calibrated and geolocated radiances).

This paper will present the Arctic Weather Satellite Programme, its current status, Space Segment and Ground Segment Designs, AWS services, including data products and the overall planning of the AWS constellation preparation.

The European Space Agency (ESA) Arctic Weather Satellite (AWS) programme is currently on going with OHB Sweden as the prime contractor responsible of the development of the AWS Space Segment and Ground Segment. The AWS prototype satellite launch is planned in 2024, hosting a 19-channels cross-track scanning microwave radiometer, covering frequencies from the microwave to the sub-mm wave range.
EUMETSAT and ESA share an interest in small satellites equipped with microwave sounders complementing the EUMETSAT Polar System Second Generation (EPS-SG) Microwave Sounding mission supported by the Microwave Sounder (MWS). A successful outcome of the AWS in-orbit demonstration in 2024-2025 time frame would represent an opportunity for EUMETSAT to expand the products’ envelope of the EPS-SG mission for the users, by implementing a constellation of satellites with microwave sounding capability supporting global and regional numerical weather prediction (NWP) applications. This constellation would be consistent with the vision for WIGOS in 2040 and the EUMETSAT Strategy for 2030. EUMETSAT and ESA have been cooperating on AWS since 2020 with the aim to prepare for a possible future constellation, which would be flying recurrent models of the AWS prototype. The Phase 0/A activities for the constellation definition are currently ongoing at EUMETSAT.
This presentation provides an overview of the status of phase 0/A activities for a potential future constellation based on AWS. The EUMETSAT AWS constellation would be developed in cooperation with ESA. This mission is expected to operationally provide information on global humidity and temperature profiles by delivering sounding data in near real time to the users with unprecedented revisit time.
The presentation will also highlight the main drivers of the system architecture taking into consideration the draft End User Requirements, which are under preparation. It will describe the current assumptions regarding the constellation architecture: i.e. number of satellites, orbits and crossing time at the equator and expected coverage along with replenishment and deployment strategy. It will provide an outlook of the logic and planning for the approval of the mission, with an overview of the relevant scientific studies aimed at demonstrating the impact of such a constellation.

The European Space Agency’s (ESA) Aeolus satellite was launched on 22 August 2018 from Centre Spatial Guyanais in Kourou, French Guyana. The Aeolus data has been extensively analysed by a number of meteorological centres and found to have a positive impact on NWP forecasts, particularly in the tropics and polar regions. These positive results, along with the successful in-orbit demonstration of the measurement concept and associated technologies utilised on Aeolus, resulted in a statement of interest from EUMETSAT in a future, operational DWL mission in the 2030 to mid-2040’s timeframe and a request to ESA to carry out the necessary pre-development activities for such a mission. This paper will describe the current status of instrument pre-development activities that are being performed in the frame of a potential Aeolus Follow-On mission (Aeolus-2) and ESA’s plans for such a mission. 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 a mission lifetime higher than 10 years utilizing 2 spacecraft (implying a lifetime of 5.5 years for each) with a launch of the first satellite in 2030, increased robustness and operability of the instrument, and an emphasis on reduction of recurrent costs; the maximum utilisation 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 requirements which have been used as the basis for a dedicated Instrument Consolidation Study. An extensive review and trade-off of the above inputs by Airbus Defence & Space, ESA, and independent experts, resulted in the decision to baseline a bi-static instrument design. The various trade-offs that led to the choice of bi-static design are discussed. In addition, three instrument subsystem pre-development activities are currently running: two laser transmitter pre-developments and the pre-development 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 Aeolus-2 mission. The status of these pre-developments will be summarised and presented together with ESA’s plans for an operational Aeolus-2 mission.

This presentation introduces the EUMETSAT activities on a possible operational Doppler Wind LIDAR (DWL) mission based on the Aeolus-2 instrument & spacecraft currently under development by ESA.

This new DWL capability is intended as an expansion of the EUMETSAT Polar System Second Generation (EPS-SG) programme.
Originally identified as one of 20 candidate observation missions by the 2008-2009 EPS-SG User consultations, it was eventually not down-selected at the time as part of the Metop-SG payload complement mainly due to its low maturity.

Since then, the picture significantly evolved thanks to the 2018 launch of the ESA-Aeolus mission, demonstrating the maturity of space based DWL concept, as well as by showing significant and substantial beneficial impact in global NWP models as reflected by the operational assimilation of its data by several major European NWP centres since 2019.
On those bases, EUMETSAT and ESA agreed to establish a joint study roadmap on a possible operational DWL mission and to, in parallel, coordinate the assessment of the impact of Aeolus measurements on NWP.

In 2020, while ESA started a series of technology pre-developments and instrument & satellite studies, EUMETSAT initiated system phase 0/A activities with the objectives to assess the integration of such operational mission in its operational framework and begin the formulation of high-level mission, system & ground segment requirements.

By now, EUMETSAT and ESA jointly compiled an initial draft End User’s Requirement Document (EURD) based on mission observational requirements proposed by the Aeolus SAG (ASAG) directly derived from the Aeolus mission requirements.
The EUMETSAT system and ground segment architectural definition is also progressing with the objective to maximize the reuse of EUMETSAT assets to allow for a cost-effective mission.
As for the Aeolus data impact assessment on NWP, it is now ongoing, supported by a series of scientific studies and workshops.

Finally, EUMETSAT and ESA are also closely coordinating the preparation of their respective programme proposals while defining possible cooperation framework.