Call for ground-based reference CO₂ and CH₄ data provision service in support of Copernicus CO2M Validation

As part of the Copernicus component of the EU Space Programme, the European Commission and the European Space Agency (ESA), are expanding the Copernicus Space Infrastructure and are implementing satellite remote measurements to support anthropogenic Carbon dioxide (CO₂) emission monitoring. In support of well-informed policy decisions and to assess the effectiveness of strategies for CO₂ (and methane (CH₄)) emission reduction, uncertainties associated with current anthropogenic emission estimates at national and regional scales need to be reduced. Satellite measurements of atmospheric CO₂ and CH₄, complemented by in-situ measurements and bottom-up inventories will be integrated in an advanced (inverse) modelling scheme to provide a transparent and consistent quantitative assessment of their emissions and their trends at the scale of megacities, regions, countries, and at global scale.

The European Organization for the Exploitation of Meteorological Satellites (EUMETSAT) is responsible for the development of the operational ground segment (with contributions from ESA) and the CO2M system operations during commissioning and the routine phase.

The CO2M mission targets the provision of observations globally with, on average, a weekly effective coverage over land for a single platform at latitudes above 40 degrees, at 4 km² spatial resolution, and a precision better than 0.7 ppm in XCO₂ and 10 ppb in XCH₄. Global effective coverage within 3 to 4 days is targeted for a constellation of three platforms. Operational validation and monitoring of those products requires the development and operations of scientific validation methods, as well as the establishment of a framework for the continuous provision of ground-based reference data to support the needs of the CO2M Cal/Val facility and the scientific validation of CO2M greenhouse-gas (GHG) products.

In this context the Royal Belgian Institute for Space Aeronomie (BIRA-IASB) is tasked by EUMETSAT on behalf of the European Commission with implementing a data provision service to the EUMETSAT operational Cal-Val facility comprising fit-for-purpose data of dry-air column weighted abundances of Carbon Dioxide and Methane (XCO₂ and XCH₄) from ground-based solar absorption measurements satisfying a number of criteria as outlined below.

Requirements for ground-based reference greenhouse gas data for CO2M product validation and continuous monitoring

The following data-service level requirements apply:

• Timeliness of incoming level-2 products shall be better than 1 week (threshold) / 3 days (goal) for network approved reference data ([RD-1]).
  
  
• Timeliness of incoming level-1 data (if provided) shall be better than 3 days ([RD-1]).
  
  
• Availability of data shall be better than 80% out of the number of potentially available cloud free measurements ([RD-1]).^[1]
  
  
• The product quality shall fulfil the product quality criteria in precision and accuracy as outlined in the CO2M Ground-Based Network Reference Product Performance Requirements document ([RD-1]).

Details on requirements to be fulfilled for all these criteria (with applicability of requirements depending on data level) are provided in the CO2M Ground-Based Network Reference Product Performance Requirements document ([RD-1]).

^[1] The overpass times will be provided to all station providers as input.

Funding and additional advantages for the Data Providers 

Data-providers signing a service contract with BIRA-IASB will receive a fee for the data provision depending on the data category and type of site, provided that the requirements outlined above are fulfilled, as detailed in a dedicated service level agreement with BIRA-IASB.

In addition, Data-providers will be acknowledged in CO2M validation reports and co-authorship will be offered in case of peer-reviewed publications, gain early access to validation analyses where applicable and required. In addition, EUMETSAT will support Data-providers in applying for national funding for their sites as required to carry out and sustain the associated measurements.

Organizational Framework

The Karlsruhe Institute for Technology (KIT) are providing EUMETSAT with a scientific service for the development of a prototype central ground-based data processing facility to process reference measurements from TCCON and COCCON, tailored to the specific requirements of CO2M. Using this prototype as input, a consortium led by BIRA-IASB, and including S&T Netherlands B.V. (S&T) and Matthias Buschmann Environmental Research (MBER), will be responsible for the operational collection and processing of the ground-based measurements.

• BIRA-IASB…. are establishing and administering a ground-based network-data provision framework, enabling the sustainable and timely provision of relevant data, including the necessary funding support and data management policy and the methods for contractual and financial management. Contracts with the individual data providers will be placed and managed by BIRA-IASB. BIRA-IASB will also be responsible for the infrastructure, software and operational data processing to process the NDACC Ground-Based Products (GBP) from level 0 to generate the CO2M tailored products.
  
  
• MBER …..are implementing the infrastructure, software and operational data processing to process the Ground-Based Products (GBP) from level 0 or level 1 data and generate the CO2M tailored products.
  
  
• S[&]T …… are providing the interface to provide the GBP data to the EUMETSAT Cal/Val Facility.

Usage of data for CO2M product Cal/Val

The expected operational data flow to produce the CO2M XCO₂ and XCH₄ GBPs is schematically illustrated on Figure 1, where from left to right: the TCCON and COCCON sites deliver near real-time (NRT) low-level observation data to MBER for processing into level-2 data, using chemical and meteorological priors either from Caltech (as per standardised TCCON processing) or from EUMETSAT (customized CO2M priors). TCCON and COCCON low-level data should include the FTIR interferograms (level-0) or spectra (level 1) and auxiliary data (e.g. surface pressure).  From these NRT data, XCO₂ and XCH₄ will be produced using either standard or custom retrieval configurations (e.g. different prior). In addition, level-2 TCCON and COCCON data will also be collected from the sites by MBER. Level-0/ level-1 and level-2 data will then be pushed to S[&]T for archival and dissemination to the EUMETSAT CO2M Cal-Val Facility. In a separate flow, the NRT low-level observation data from NDACC-IRWG sites will be delivered to BIRA-IASB for processing into level-2 data, using customized CO2M priors. The NDACC-IRWG low-level data should include the FITR interferograms (level-0) or spectra (level-1) and auxiliary data (e.g. surface pressure). Level-2 CH₄ data from the NDACC-IRWG sites will then be pushed to S[&]T for archival and dissemination to the EUMETSAT CO2M Cal-Val Facility.

 Figure 1: Schematic flow of the CO2M XCO₂ & XCH₄ GBP processing and delivery from the ground-based reference networks

Once operational, the performance of this data processing flow will be monitored to gauge the reliability and quality of the CO2M GBPs, as well as their delivery to EUMETSAT. 

Who Can Contribute

Submissions are invited from all principal investigators (PIs) producing ground-based data that are, or will be, capable of fulfilling the requirements ([RD-1]), from instruments producing data under network approved standards from networks such as TCCON, COCCON, NDACC and Pandonia; and following the CEOS FRM frameworks (Goryl et. al., 2017; Sha et. al., 2024).

Expected start of service

Following the successful signing of a data-provision contract with BIRA-IASB as entrusted entity by EUMETSAT and Copernicus, the site PIs will be invited to an implementation phase where examples of data file exchange would be requested to set up the data flow and processing chain for participating sites. Pending an expected launch of the first CO2M platform by end of 2027, the currently expected start of regular data provision is expected for Q3 2027 with a commissioning phase for the data-service expected to last four months, then entering the operational phase by January 2028.

Details on Measurement type and data Requirements

The following measurement and instrument types and associated data products are eligible for support (non exclusive!):

During the setup phase additional metadata and instrument specific data will be requested from the participating site PIs.

In case of a TCCON site, here are some examples of specific information that will be asked from the site PIs for the retrieval – site_sunrun.dat, site_cell_status_info.dat, site_oof_header.dat, site_manual_flagging.dat, site_qc.dat. In addition, some other metadata like contacts, acknowledgement text to be included in the level 2 files would be asked from the site PIs.

In case of a COCCON site, a set of .yml files containing all site-specific information necessary for the retrieval will be asked from the site. The example .yml files provided in the proffastpylot retrieval examples should be used as a template.

In case of a NDACC site, here are some examples of specific information that will be asked from the site PIs for the retrieval – instrument serial number, link to existing instrument ID on NDACC as mandatory; cell measurements (opus files), cell ID used, sunrun file as optional parameters. File names (OPUS and meteorological data) must contain “yyyymmdd”.

The level-2 files will be processed in the network standards and provided to EUMETSAT.

Summary of Ground-Based Product Performance Requirements from [RD-1]

Expected product quality performances, timeliness and availability of CO2M GBPs are specified separately for threshold (T) and goal (G) achievements in the CO2M Ground-Based Network Reference Product Performance Requirements ([RD-1]). The specifications for XCO₂ and XCH₄ GBPs are reproduced here for the sake of completeness.

Product performance

Rationale:

COCCON requirements – As the COCCON calibration is derived from the TCCON calibration via intercomparison of long-term COCCON time series with TCCON at several TCCON sites, it shares the accuracy limitations of TCCON. As there always can be some error imported by the connection procedure (e.g. due to the smoothing error generated by imperfect a-priori gas distribution or by the fact that the EM27/SUN units used for establishing the connection not ideally depict the network-average COCCON spectrometer behaviour), the COCCON calibration is therefore slightly inferior to TCCON.

NDACC requirements – Methane systematic error is currently estimated at 1 % and mostly due to spectroscopy used. Systematic uncertainties could be improved by applying a calibration factor. A network wide determination of the calibration factor for NDACC methane could be part of a dedicated work package.

Requirements on the ground-based product timeliness for all networks:

The ground-based network shall make the raw data products (either level 0/1) available to the EUMETSAT central facility within 1 week (target) / 3 days (goal) of collection.

The level 2 NDACC XCH₄ product can be retrieved from the raw data and made available to the EUMETSAT central facility within 1 week (target) / 3 days (goal) if CAMS pressure-temperature is used and 2 week (target) / 10 days (goal) if NCEP pressure-temperature is used upon receipt of level 0 data.

Requirements on the ground-based product availability for all networks:

The ground-based network data availability shall be better than 80 % of the CO2M constellation platform station “overpasses”, under cloud-free conditions, and within an observation time window of ± 1 h per platform.^[1]

Licensing and Data Policy

While the Intellectual Property Rights (IPR) associated to delivered ground-based data and products will remain with their Principal Investigator (PI), an irrevocable, non-exclusive, royalty-free license should be granted to EUMETSAT to use such data and products for any non-commercial scientific, validation and calibration purposes directly related to Copernicus CO2M mission. This license should include the rights to archive, process, and distribute the data within the Copernicus programme framework, but shall not permit the commercialisation or any other commercial exploitation of the deliverables (or derived products) without the prior written consent of the IPR owner. 

Appropriate attribution to the data provider will be ensured in any use or publication of the data.

How to Contribute/Submission Instructions

Interested contributors are invited to submit a short Expression of Interest (EOI) via the online form at https://co2m.aeronomie.be/ by 18 May 2026. The online form will be available as of 22 April 2026.

Contact

For further information, please contact BIRA-IASB at co2m-gbp-net[at]aeronomie.be.

Related Documents and Links

[RD-1] CO2M Ground-Based Network Reference Product Performance Requirements, EUM/COPER-CO2M/DOC/21/1251968, v2C. (click here to download)

Reference Documents

• Goryl, P.; Fox, N.; Donlon, C.; Castracane, P. Fiducial Reference Measurements (FRMs): What Are They? Remote Sens. 2023, 15, 5017. https://doi.org/10.3390/rs15205017

• Sha, M.K.; De Mazière, M.; Notholt, J.; Blumenstock, T.; Bogaert, P.; Cardoen, P.; Chen, H.; Desmet, F.; García, O.; Griffith, D.W.T.; et al. Fiducial Reference Measurement for Greenhouse Gases (FRM4GHG). Remote Sens. 2024, 16, 3525. https://doi.org/10.3390/rs16183525

^[1] The overpass times will be provided to all station providers as input.

Network meeting files:

EUMETSAT_CO2M_CalVal_Phase_2_NetworkCall Presentation - click here to download

Recording of the network call meeting on 21 April 2026 - click here to download