The Aeolus Data Innovation and Science Cluster

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

Data quality of Aeolus wind measurements

The European Space Agency (ESA)'s Earth Explorer Aeolus was launched in August 2018 carrying the world's first spaceborne wind lidar, the Atmospheric Laser Doppler Instrument (ALADIN). ALADIN uses a high spectral resolution Doppler wind lidar operating at 355nm to determine profiles of line-of-sight wind components in near-real-time (NRT). ALADIN samples the atmosphere from 30km altitude down to the Earth's surface or to the level where the lidar signal is attenuated by optically thick clouds. The global wind profiles provided by ALADIN help to improve weather forecasting and the understanding of atmospheric dynamics as they fill observational gaps in vertically resolved wind profiles mainly in the tropics, southern hemisphere, and over the northern hemisphere oceans. Since 2020, multiple national and international weather centres (e.g. ECMWF, DWD, Météo France, MetOffice) assimilate Aeolus observations in their operational forecasting. Additionally, the scientific exploitation of the Aeolus dataset has started. A main prerequisite for beneficial impact and scientific exploitation is data of sufficient quality. Such high data quality has been achieved through close collaboration of all involved parties within the Aeolus Data Innovation and Science Cluster (DISC), which was established after launch to study and improve the data quality of Aeolus products. The tasks of the Aeolus DISC include the instrument and platform monitoring, calibration, characterization, retrieval algorithm refinement, processor evolution, quality monitoring, product validation, and impact assessment for NWP. The achievements of the Aeolus DISC for the NRT data quality and the one currently available reprocessed dataset will be presented. The data quality of the Aeolus wind measurements will be described and an outlook on planned improvements of the dataset and processors will be provided

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

Recherche sur la Personne Efficace: Quelques Relations entre les Valeurs de Travail et de Loisir

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Level 1b error budget for MIPAS on ENVISAT

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a Fourier Transform Spectrometer measuring the radiance emitted from the atmosphere in limb geometry in the thermal infrared spectral region. It was operated on-board the ENVISAT satellite from 2002 to 2012. Calibrated and geolocated spectra, the so-called level 1b data, are the Basis for the retrieval of atmospheric parameters. In this paper we present the error budget for the level 1b data of the most recent data version in terms of radiometric, spectral and line of sight accuracy. The major changes of version 8 compared to older versions are also described. The impact of the different error sources on the spectra is characterized in terms of spectral, vertical and temporal correlation, because these correlations have an impact on the quality of the retrieved quantities. The radiometric error is in the order of 1 to 2.4 %, the spectral accuracy is better than 0.3 ppm, and the line of sight accuracy at the Tangent point is around 400 m. All errors are well within the requirements and the achieved accuracy allows to retrieve atmospheric parameters from the measurements with high quality

MIPAS Level 1B Version 8 Radiometric Accuracy Assessment

The MIPAS mission is in its post-operational phase F. A final algorithm improvement will be done along with a full reprocessing of the entire data set covering a period of ten years from 2002 to 2012. The goal is to improve as much as possible the MIPAS data quality. The new data set will be referred as version 8. The MIPAS instrument has measured Infra-Red (IR) emission spectra at the Earth's limb in the middle and upper atmosphere along the orbit during day and night. The spectral range covered is 685 to 2410 cm-1 with a spectral sampling of 0.025 cm-1 during Full Resolution (FR) period and 0.0625 cm-1 during Optimised Resolution (OR) period. The MIPAS level 1B processor transforms instrument raw data into spectra calibrated spectrally and radiometrically with geo-location determined over the earth geoid of the line of sight tangent point. This paper presents an assessment of the radiometric accuracy budget. The main contributors to the error are the detector non-linearity, the gain calibration noise and variation along time. The detector non-linearity was re-characterized in-flight and related error estimated. A validation of the new characterization was done looking at overlaps with linear channels. This has led to an improvement of level 2 trending analyses and validation. The error due to the gain calibration noise was controlled and limited through the calibration scenario. The ice accumulation in the output optics and instrument temperature variation lead to a gain calibration variation along time. The effect of ice was monitored and controlled through periodic decontamination. Compared to the requirements and the previous version, the MIPAS level 1B version 8 will have an improved radiometric accuracy

MIPAS Level 1B algorithms overview: operational processing and characterization

This paper gives an overview of the MIPAS Level 1B (L1B) processor whose main objective is to calibrate atmospheric measurements radiometrically, spectrally and geo-located. It presents also the results of instrument characterization done on ground and during the first years inflight. An accurate calibration is mandatory for high quality atmospheric retrievals. MIPAS has shown very good performance and stability. The noise equivalent spectral radiance ranges from 3 to 50 nW/(cm2 sr cm−1) and is well within the requirements over nearly the whole spetral range. The systematic radiometric error is estimated to be within 1 or 2% in most situations

MIPAS Level 1B Improvements

The MIPAS instrument measures high-resolution Infra-Red (IR) emission spectra at the Earth's limb in the middle and upper atmosphere along the orbit during day and night. The spectral range covered is 685 to 2410 cm-1 and is divided into five bands with a spectral sampling of 0.025 cm-1 during Full Resolution (FR) period and 0.0625 cm-1 during Optimised Resolution (OR) period. The MIPAS level 1B algorithm transforms instrument raw data into spectra calibrated spectrally, radiometrically and determines the geo-location over the earth geoid of the tangent point. This paper describes the level 1B algorithm modifications and improvements since last ACVE. E.g., spectral calibration, pointing, spike detection, detector non-linearity characterisation among others. The Near Real Time (NRT) processing and the mission archive reprocessing data quality was greatly improved. Finally, a summary of future planned improvements are presented

Development of Compact Calibration Infrared Sources for the Meteosat Third Generation Flexible Combiner Imager

In the frame of the Meteosat Third Generation Flexible Combiner Imager (MTG-FCI) development, ABB has designed a new kind of small infrared calibration sources offering high-end performance on emissivity, temperature knowledge and radiometric accuracy within a low mass and volume allocation. Calibration sources are critical sub-systems providing reliable and traceable data for meteorological forecasting as well as long-term climate monitoring. This applies also to next generation compact constellations in order for private data operator to provide useful data for various applications. This paper will present an overview of the blackbody design for the MTG FCI, focusing on its compactness and its validated performances. Advantages of this technology will be listed and its applicability in the context of future low-cost constellation missions will also be presented

Development and Production of the Onboard Radiometric Calibration References for the Next Generation of European Weather Forecasting Space Instruments

Eumetsat’s new generation weather satellites will include improved infrared sounders, the IASI-NG on MetOp Second Generation and the IRS on Meteosat Third Generation. The data collected by the infrared sounders will be used to obtain vertical profiles of temperature and humidity as well as other climate variables (vertical profiles of the concentration of some trace gases, surface temperatures, cloud top height, etc.). That information will then be used in numerical weather prediction models and in support of climate studies. A key feature of those instruments is to embed high end traceable calibration sources in order for the instruments to fulfill their role in producing high quality data that can be used with confidence and can be successfully compared to other instruments (past and future) for long-term climate study trends. For calibration in the infrared, the radiometric references are essentially quasi-blackbody sources: sources of high emissivity and accurately known temperature emitting energy that can be precisely predicted with Planck’s law of radiation. ABB is currently developing the onboard infrared calibration sources for all the new generation of European infrared weather forecasting space instruments in LEO or GEO orbit. That includes two blackbodies for IASI NG instrument onboard Metop-SG: BB-FTS for the sounder and BB-IIS for the cloud imager and one for the IRS onboard MTG. This paper will present an overview of these projects covering the key features of the different calibration sources, the status of their development and recent test results