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The TNA provided to the AERONET-EUROPE calibration centre offers the opportunity of calibration and maintenance for standard and polarized Cimel sun/sky photomers to any AERONET and possible future AERONET user located in Europe.

The infrastructure is composed of separate but complementary installations. The leading and entrance installation is the PHOTONS observatory located at CNRS-LOA coupled with a Météo France platform which is located in Carpentras, France. The other installations are located in Spain (GOA-UVA and CSIC-IZANA).The choice of the installation selected for calibration is decided internally and will be based on different conditions (e.g., distance between the calibration centre and the user site, instrument type, weather conditions, any pre-existing scientific agreements, etc. The main contact person for all requests for AERONET-EUROPE is CNRS-LOA (

Free service
Instrument calibration and maintenance is performed free of charge and is granted on the basis of proposals which will be reviewed by a TNA selection panel. Instrument transport from and to the user is not included and must be covered by the institution of the user.

The support to users includes:
  • post-field calibration-maintenance and pre-field calibration (incl filters, polarizers and internal battery changes for head and control box parts as well as microswitch and belt for robot)
  • final functional test at CNRS-LOA or GOA-UVA
  • calibration update of the AERONET database
  • request for QA analysis to GSFC/NASA
To be eligible for the free instrument service, the PI in charge of the photometer instrument must satisfy the following conditions:
  • The PI must be affiliated with an institution from an EU member, associated state, or candidate state. Participants from institutions outside EU member, associated, or candidate states are not eligible.
  • The home country of the PI institution must be situated in another country as the home country of the calibration installation ('transnationality' aspect).
  • The users must be entitled to publish the results from work carried out under this ACTRIS TNA activity.
Application procedure:
The call for TNA to AERONET-EUROPE is an open and continuous call. The proposals are accepted at any time and from any eligible researcher in charge of a sun photometer deployed for long-term measurements. Users interested in this service should send an AE-TNA proposal form by email to AERONET-EUROPE ( at least 2 months before the planned project start.
In case of new instruments (not yet purchased or purchase in process), arrangements must be made between Cimel and the calibration infrastructure to enable calibration of the instrument before transmission to the future PI. Prior contact with AERONET-EUROPE is indispensible in this case.

Evaluation procedure:
  1. Incoming proposals are verified by the Coordination Office for formal compliance with the EU regulations.
  2. The proposals are sent to the principal AERONET-EUROPE contact person at CNRS-LOA to confirm feasibility of the project.
  3. The proposals are forwarded to an independent TNA selection panel for peer-review based on defined criteria. The TNA panel is composed of international experts with strong expertise in the field to evaluate and select the proposal according to clearly defined selection criteria (see below).
  4. The applicant is informed of the final decision by the ACTRIS Coordination Office.
  5. CNRS-LOA will be in charge of contacting the user for the subsequent steps (choice of installation, reception of instrument, etc.).
Selection criteria:
The TNA selection panel reviews the proposals with respect to the following criteria:
  • Originality and scientific quality
  • Interest to scientific community
  • Geographical location of user site
  • Available instrumentation at atmospheric station
User obligations:
After successful calibration-maintenance service, the PI of the AE-TNA project supported under ACTRIS is requested to provide appropriate documentation to the Coordination Office.  The documentation will allow  justifying the provision of the service, including records of user details (name, nationality, home institution of users as well as a summary of the scientific/technical objectives and achievements.

Once calibration/maintenance is achieved, the QA data/products will be made available via the AERONET website. To ensure production of QA data, the user agrees to the following obligations:
  • to perform weekly local maintenance of the instrument following AERONET rules,
  • to perform weekly check of instrument status available at
  • to reply immediately in case of instrumental problems detected by any of the calibration centres.

The instrument will not be released until submission of all necessary documentation. Instrument shipping back to the user site must be covered and managed by the user.

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