One of the main objectives of the FRM4 DOAS project is to develop a centralised NRT (near-real-time/6-24h latency) processing system for MAXDOAS instruments operated within the international Network for the Detection of Atmospheric Composition Change (NDACC). The target species for the first phase of the project are tropospheric and stratospheric NO2 vertical profiles, total O3 columns, and tropospheric HCHO profiles. Although the NRT MAX-DOAS centralized processing system will be demonstrated on a limited number of stations from project partners, it will be designed to allow efficient ingestion and processing of radiance spectra (Level 1 data) from a large number of instruments and sites not part of the initial project. The system will also allow for extension to additional species such as SO2, CHOCHO, HONO and H2O. A general overview of the FRM4DOAS service is given below.

user oriented frm4doas flowchart v7

  Participants joining the FRM4DOAS Service as data providers will benefit from the following advantages:

  • Free-of-charge systematic Level 1 (radiance spectra) to Level 2 (vertical columns and profiles) NRT processing service

  •  Only 6-24h latency between the submission of the spectra and the availability of final products data files

  •  Continuous quality monitoring for both Level 1 and 2 data with automated feedback to instrument PI in case of anomaly

  •  Increased data visibility as part of an international network (NDACC)

  •  Collaboration to international operational validation projects, e.g. in the frame of Copernicus

  •  Processed level-2 data for scientific use by instrument PIs but also by the overall scientific community

In return of the processing service, instrument PIs will commit to follow the FRM4DOAS guidelines and standards in terms of best practices, data acquisition protocol, and QA/QC for instrument calibration and operation. The protocol for participation to the FRM4DOAS Service will be described in a living document made available at To protect the Intellectual Property Rights of the instrument PIs and avoid any misuse of the generated data sets, a strict data policy will be applied

Beyond the on-going initiating two-year project, ESA plans to financially support the operations and developments for FRM4 DOAS, as well as a contribution to the operational MAX-DOAS activities, to ensure the long-term availability of a harmonised atmospheric composition data set. In order to assess the current MAXDOAS network in terms of  instrument calibration and operation and to identify the potential candidate instruments for future inclusion in the FRM4DOAS processing system, a dedicated questionnaire has been created and is made available below:

FRM4DOAS questionnaire (Word version)

FRM4DOAS questionnaire (pdf version)

It is kindly asked to MAXDOAS instrument(s) PIs to fill this questionnaire indicating their interest for eventual future participation in the FRM4DOAS processing system and to return it by e-mail to François Hendrick from BIRA-IASB (This email address is being protected from spambots. You need JavaScript enabled to view it.This email address is being protected from spambots. You need JavaScript enabled to view it.).