Enhanced Retrieval of Aerosol properties: Algorithm prototype for 3MI mission

This study aims to provide support for the definition of an algorithm baseline for 3MI.

The 3MI design and heritage comes from the POLDER/PARASOL missions. A number of mature algorithms exist in the community for retrieval of aerosol optical properties from POLDER/PARASOL, which could, in principle, be applied to 3MI data. However, 3MI presents a particular challenge due to the need to provide near real-time data products (~120 minutes after sensing) combined with an increase in spatial resolution which increases the data rate and, therefore, computational cost of product generation. Plus, 3MI has additional spectral channels (specifically in the ultraviolet and the short-wave infrared) and more polarised channels than its predecessors. 3MI also has stringent requirements on its final product quality.

The most sophisticated POLDER/PARASOL algorithms, which would be capable of producing high quality products, and which make use of not only co-registered multi-spectral, multi-angular, multi-polarisation data, but also spatial and temporal accumulations, are typically too computationally expensive to be appropriate for Near Real-Time (NRT) operational product production. Conversely, look-up-table methods, which are sufficiently fast for NRT product production, are unlikely to reach the accuracy required for 3MI data products.

The aim of this study is to provide support to the development of aerosol optical and microphysical properties retrieval algorithms from the 3MI instrument on EUMETSAT Polar System – Second Generation (EPS-SG).

Data Resources
Study Meetings



The main objective of this study is to provide support for the definition of an algorithm baseline for 3MI, which will be sufficiently fast to be able to be run in near real-time, and sufficiently accurate to satisfy the product quality requirements. A secondary objective is to evaluate the impact of the choice of Level 1b to 1c methodology on the final Level 2 products, by comparing results generated from the EUMETSAT 3MI Level 1c product and an independent 3MI level Lc product, provided by the contractor.


This study will provide support for the definition of an algorithm baseline for 3MI, which will be sufficiently fast to be able to be run in near real-time and sufficiently accurate to satisfy the product quality requirements. This support will comprise provision of a review of aerosol models to be used in the retrieval, provision of proxy test data for algorithm evaluation, and provision of a test environment, capable of processing multiple orbits of 3MI test data in a reasonable timeframe, for evaluation of algorithm performance.

The contractor will have the capability for Level 1b to Level 1c data processing and a state-of-the art aerosol microphysical and optical properties retrieval algorithm (supported by peer-reviewed publications) to serve as a reference processor for algorithm testing and performance evaluation (both in terms of product accuracy and processor speed). The contractor is required to base its aerosol optical and microphysical properties retrieval on radiances using multi-angle acquisitions, up to 14 acquisitions, 'views' (see Figure 1). These are co-registered to a regular, equal area, fixed geo-physical grid with configurable grid spacing, close to the instrument footprint spatial resolution (Level 1c data); are parallax corrected using a digital elevation model of sufficient resolution, and are covering the full instrument swath. The co-registration is done separately for SWIR and VNIR channels with a maximum of 14 acquisitions for both.

Since the along-track dimension of the SWIR detector is half the size of the VNIR its viewing angle range along-track is restricted to half of the VNIR detector and, therefore, the detectors share only seven out of 14 viewing angles which are identical to the VNIR angles. Specific METimage cloud products, namely the cloud mask and cloud top height information, will be available as an input to the 3MI NRT aerosol product processing chain.

Figure 1
Figure 1: The 3MI concept, multi-view, multi-spectral, and multi-polarisation sampling


Phase Details
Kick-Off 15/05/2016
Duration 15 months
Status Ongoing
WP1 Review of Aerosol Models
Completed: 30/05/2016
WP2 Preparation of Test Data
Completed: 30/09/2016
WP3 Testing of Baseline EUMETSAT Look-up Table Algorithm
Completed: 12/05/2017
WP4 Proposal for Enhanced Aerosol Retrieval Algorithm
Completed: 07/12/2017
WP5 Testing of Enhanced Aerosol Retrieval Algorithm
Completed: 19/04/2018
WP6 Evaluation of EUMETSAT Co-registration Function
Planned: June 2018

Data Resources

For data inquiries, please contact Dr Bertrand Fougnie.

Study Meetings

Phase Date and location
KO 02/05/2016, WebEx
PM1 30/05/201, WebEx
PM2 30/09/2016, EUMETSAT
PM3 12/05/2017, LOA, Lille, France
PM4 07/12/2017, WebEx
PM5 19/04/2018, LOA, Lille, France
PM6 Planned Q2/2018, LOA, Lille, France
FR Planned Q2/2018, EUMETSAT


1st International Workshop on “Advancement of polarimetric observations: calibration and improved aerosol retrievals” (APOLO2017), Hefei, China, 24–27 October, 2017.


EUMETSAT plans for an aerosol product suite to serve the operational aerosol user community

The EPS-SG 3MI co-registered level-1C and surface reflectance level-2 product


EUMETSAT Project Manager
Dr Rosemary Munro
Competence Area Manager
Remote Sensing and Products Division
Dr Oleg Dubovik
Laboratoire d’Optique Atmosphérique, Université de Lille, France
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