CEOS Cal/Val Portal explanation

The CEOS Cal/Val Portal:
Calibration and Validation activities
around space-borne sensors.
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The CEOS CalVal portal serves as the main forum for exchange and information sharing for the CEOS Working Group on Calibration and Validation. In additions, it provides access to agreed good practices and Cal/Val protocols to the wider Earth Observation community within CEOS and beyond. It connects users to reference data and networks and provides reliable, up-to-date and user friendly information useful for Cal/Val tasks, facilitating data interoperability and performance assessment through an operational CEOS coordinated & internationally harmonised Cal/Val infrastructure consistent with QA4EO principles.


Back CINDI-3 Campaign

The Third Cabauw INtercomparison of DOAS-like Instruments (CINDI-3)

We are pleased to announce the Third Cabauw INtercomparison of DOAS-like Instruments (CINDI-3), that will take place in Cabauw (The Netherlands) during four weeks from May 21 until June 22, 2024.

CINDI-3 is a community-wide intercalibration campaign of ground-based UV-Visible DOAS instruments measuring the atmospheric column and profile of NO2 and O3, complemented by mobile-DOAS observations and an exhaustive range of measurements of aerosols, NO2, O3 and other UV-Visible trace gases of interest like HCHO, CHOCHO, HONO, BrO and H2O. The campaign also includes an airborne component for the characterization of the 3D variability of the NO2 field and of urban emission sources in the surroundings. Like for the previous CINDI campaigns the experiment will be carried out on the Cabauw Experimental Site for Atmospheric Research (CESAR) located 20 km south-west of Utrecht. This sub-urban site is influenced by emissions from surrounding Dutch cities, which ensures a large variability in tropospheric NO2 with reasonably small spatial gradients.

CINDI-3 is organised under the joint umbrella of the ACTRIS Research Infrastructure, ESA and the Network for the Detection of Atmospheric Composition Changes (NDACC). Conducted as a semi-blind intercomparison campaign with an external referee, CINDI-3 aims at the intercalibration of atmospheric trace gas UV-Visible remote-sensing systems in view of consolidating the international participation to ACTRIS and NDACC, and of establishing Fiducial Reference Measurements (FRM) suitable for the validation of current and future satellite missions of the CEOS Air Quality and Ozone constellations. If you wish to participate in the measurement campaign please express your interest to Michel.VanRoozendael at with cc to Arnoud.Apituley at and Karin Kreher at

Preliminary information on the campaign can be found using this link.