Welcome to the FRM4DOAS website

Fiducial Reference Measurements (FRM) are a suite of independent, fully characterized, and traceable ground measurements that follow the guidelines outlined by the GEO/CEOS Quality Assurance framework for Earth Observation (see http://qa4eo.org). These FRM provide the required confidence in data products, in the form of independent validation results and satellite measurement uncertainty estimation, over the entire end-to-end duration of a satellite mission (more information available here).

The Fiducial Reference Measurements for Ground-Based DOAS Air-Quality Observations (FRM4DOAS) is a 2-year ESA project which started in July 2016. It aims at further harmonization of MAX-DOAS systems and data sets, through the

  • specification of best practices for instrument operation
  • demonstration of a centralised NRT (near-real-time/6-24h latency) processing system for MAX-DOAS instruments operated within the international Network for the Detection of Atmospheric Composition Change (NDACC)
  • establishment of links with other UV-Visible instrument networks, e.g. PGN

The target species for the first phase of the project are tropospheric and stratospheric NO2 vertical profiles, total O3 columns, and tropospheric HCHO profiles. The aim is to produce homogenous ground-based reference datasets from instruments being operated at long-term monitoring sites (e.g. NDACC) or during field campaigns. Such reference data sets will play a crucial role in the validation of future atmospheric composition satellite missions, in particular the ESA Copernicus Sentinel missions S-5P, S-4, and S-5.


Image courtesy of A. Piters (KNMI)


The FRM4DOAS project was funded under the ESA contract n°4000118181/16/I-EF.


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