Estonia has been awarded its first contract since becoming an ESA Member State in 2015. Over the next three years, scientists from Estonia's Tartu Observatory will head an international team to ensure that Sentinel-3's measurements of ocean colour are of the highest quality possible.

More than ever, measurements from satellites are being used for applications to improve everyday lives and for scientific discovery. It is essential that the integrity of these measurements is maintained to international standards.

ESA therefore goes to great lengths to ensure that this 'behind the scenes' quality-control work - in the form of instrument calibration and data validation - is carried out before a satellite is launched and throughout its life in orbit.

However, maintaining accurate and traceable ground-truth measurements is a major challenge for ocean-colour instruments, demanding detailed characterisation and extensive international collaboration.