Project Description

The ECAMS (EarthCARE ATLID and MSI Instruments Synergy for Advanced Retrieval of Aerosol Vertical Profiles) project focuses on enhancing aerosol vertical profiling through the integration of active and passive satellite measurements. By combining data from EarthCARE’s ATLID (Atmospheric LIDar) and MSI (Multi-Spectral Imager) with PACE mission’s polarimeters (SPEXone and HARP-2), ECAMS aims to develop a robust retrieval framework to improve global aerosol characterization. The motivation for combining passive and active instruments lies in their complementary capabilities: passive sensors provide sensitivity to atmospheric aerosol amounts and, to a certain extent, particle size, shape, and morphology, while active sensors offer detailed vertical profiles, enabling a more accurate and comprehensive understanding of the global distribution of aerosol properties.

A key goal of ECAMS is to implement a flexible retrieval approach that adapts to various satellite configurations, paving the way for future missions. The project focuses on optimizing aerosol and measurement models and validating its methods using data from EarthCARE, PACE, and ground-based observations. It emphasizes the precise estimation of aerosol optical depth and vertical profiles, adhering to established climate standards and ensuring adaptability for diverse remote sensing applications.

ECAMS aims to introduce innovative synergetic retrieval methods using the GRASP (Generalized Retrieval of Atmosphere and Surface Properties) open-source software, integrating multi-instrument data for comprehensive aerosol analysis. The developed synergetic concept will be designed to be easily ported and adapted for processing various types of satellite observations with different spatial, vertical, and spectral resolutions, as well as different spectral ranges. It will serve as a community platform for advancing the remote sensing of atmospheric vertical structure and surface, providing a virtual laboratory for various remote sensing developments and applications.

This project also supports ongoing synergy developments in the ESA AIRSENSE project and complements studies on aerosol-cloud interactions in collaboration with the EC CleanCloud and CERTAINTY projects.

Project Objectives

Objective 1. Full implementation of L1 synergetic retrieval using passive and active satellite measurements, which can be robustly applied to present and future satellite observations.

Objective 2. Identifying the most appropriate passive and active satellite measurements configurations and the best models for aerosol and surface used in the synergetic retrieval:

  • testing and intercomparison of products using different GRASP approaches for modelling of aerosol and surface, with varying details on aerosol columnar and vertical properties, as well as testing optimal approaches for describing and retrieving underlying surface parameters.
  • inter-comparison of the aerosol products retrieved with the synergetic approach with different ATLID products (e.g., attenuated backscatter, extinction+backscatter and volume depolarization).

Objective 3. Testing and validation of the developed approach on MSI and ATLID data, as well as data provided by PACE polarimeters (i.e. SPEXone and HARP-2), and inter-comparison with available vertical profile aerosol products, e.g.:

  1. from co-located ground-based observations,
  2. independent EarthCARE products, or
  3. L2 EarthCARE+PACE synergies being developed in the frame of AIRSENSE project.

Fig 1. Illustration of the project objectives

Approach

Lidar observations provide limited information on detailed aerosol properties like size and composition compared to passive observations. Most lidars measure attenuated elastic backscattering at the same wavelengths they emit, which is influenced by various aerosol properties. Interpreting this data is challenging and requires substantial prior knowledge about aerosol properties (see, e.g. Klett, 1981, Kim et al., 2018, Wandinger et al., 2023). More advanced lidar systems with polarization capabilities provide information on particle shape, while high spectral resolution lidar (HSRL) systems can differentiate between Mie and Rayleigh scattering [Hair et al., 2008].

Several algorithms, like LiRIC (LIdar-Radiometer Inversion Code) [Chaikovsky et al., 2016] and GARRLiC [Lopatin et al., 2013], have been proposed to combine ground-based photometric and lidar observations to achieve a more comprehensive aerosol analysis. LiRIC and GARRLiC, for instance, use data from multi-wavelength lidars and Aerosol Robotic Network (AERONET) Sun-sky-scanning radiometers to extract vertical  concentration profiles of fine and coarse aerosol components, as well as other column-integrated aerosol properties. However, the original GARRLiC, which later merged with GRASP [Lopatin et al., 2021], was designed for specific ground-based observations and did not accommodate different lidar types (e.g., depolarization or HSRL), or offer the flexibility needed for integrating various lidar observations with passive measurements in space-based remote sensing. This integration remains a substantial challenge.

The proposed approach suggests modifying the open-source GRASP code to accommodate next-gen HSRL lidar data provided by ATLID instrument on board of EarthCARE mission. Thus, a well-established “model” approach that treats atmospheric aerosol as an external mixture of several species with predefined mirophysical properties (such as size distribution, complex refractive index and shape) that already had proven to be fruitful to retrieve atmosphere and surface parameters from various passive satellite sensors (POLDER, MERIS, AATSR, OLCI/S-3, TROPOMI/S-5p, Himawari), as well as their synergies [Litvinov et al., 2025, Lopatin et al., 2025], could be applied to MSI and PACE multi-angular polarimeters data and synergetically combined with a detailed vertical distribution as discussed by Lopatin et al., 2021.

The inclusion of a synergetic active and passive satellite retrieval approach into GRASP open-source software introduces a number of highly promising perspectives. Indeed, grace to the generalized concept of the GRASP, the following methodological tools will be available:

  1. The developed synergetic concept could be easily ported and adapted for processing various types of satellite observations with different spatial, vertical and spectral resolutions as well as different spectral ranges. 
  2. The implemented synergetic approach will work over different Earth surfaces: land, water/ocean and coastal zones. 
  3. In general, the GRASP synergetic retrieval approach will be open for wide use and can serve as a community platform for further elaboration for advancing atmosphere vertical structure and surface remote sensing.

In this regard, the approach for synergetic retrieval from the combined passive and active satellite measurements can be considered as a virtual laboratory for different kinds of remote sensing developments and applications.

Consortium

The project consortium comprises of GRASP SAS as a prime and NOA as a subcontractor.

GRASP SAS shorten from ‘Generalized Retrieval of Atmosphere and Surface Properties” was founded in 2015 with the main goal of development of remote sensing algorithms and scientific methods for environment studies of atmosphere and surface of the Earth. 

GRASP SAS will lead management and software developments in the project, as well as provide necessary assistance and in subcontractor activities. GRASP SAS specializes in developing remote sensing algorithms for studying Earth’s atmosphere and surface. Birthed from efforts by CNRS and the University of Lille, the core idea is realized in GRASP-OPEN, an open-source software. GRASP SAS focuses on algorithm development for comprehensive atmospheric and surface analysis from various remote sensing sources, scientific consulting, and supporting the GRASP open-source code. Collaborating with global organizations like ESA, NASA, and JAXA, their objective is to enhance understanding of atmospheric and surface properties affecting Earth’s climate. 

NOA (with the group of Remote sensing of Aerosols, Clouds and Trace gases (ReACT), operating under the Institute for Astronomy, Astrophysics, Space Applications and Remote Sensing (IAASARS)) utilizes the synergy of ground-based and space-borne remote sensing along with theoretical models to understand the complex aerosol-cloud-radiation interactions, towards understanding the related effects on climate and extreme weather. NOA will lead data selection, preparation and analysis, utilizing its experience in Cal/Val activities of space profilers, and provide feedback and assistance to the prime contractor, utilizing and expanding its experience with the GRASP algorithm. NOA is a renowned institution with over 170 years in science and education, specializing in atmospheric observations. Within NOA’s IAASARS, the ReACT group focuses on remote sensing of aerosols, clouds, and trace gases, using advanced observations in the Mediterranean. Their expertise encompasses aerosol remote sensing, lidar system design, and aerosol transport modeling. They’ve developed lidar systems for Cal/Val of ESA missions, participated in projects like LIVAS and CORAL, and organized ESA campaigns for satellite Cal/Val and assessment of aerosol and cloud characteristics. Additionally, ReACT manages Greece’s PollyXT lidar system, and operates the Remote Sensing section of the PANGEA climate observatory, and is a member of EARLINET and ACTRIS.

Data

First datasets will become available yearly 2026.