Sentinel-3 Tandem for Climate
After 2 years in orbit, the Sentinel-3A satellite from the Copernicus program was joined by Sentinel-3B. During the first six months of the mission, the two satellites flied in close formation. Sentinel-3A and Sentinel-3B observed the same place on the Earth within 30 seconds.
This so-called tandem phase makes it possible to inter-calibrate very accurately the two satellites in order to ensure that their measurements are consistent. In the long run, this will help to build reliable measurement records to study climate change effects such as sea level rise, increase of ocean surface temperature, or variations in the phyto-plankton distribution.
The Sentinel-3 Tandem for Climate is an ESA-financed study which aims at a detailed understanding of the inter-satellite discrepancies, differences and uncertainties using data acquired during the Tandem phase. The study is performed by a consortium of companies and research institutes led by ACRI-ST.
In order to better estimate inter-satellite differences and prototype harmonization procedures, a custom reprocessing of Sentinel-3 Optical instruments has been performed during Summer 2019. A sample of data from the tandem and drift phases has been reprocessed using improved calibration coefficients: optimized geometric calibration for SLSTR-B, improved radiometric and geometric calibration for OLCI-A and B. In this experiment, we have aligned the radiometry of OLCI-A on that of OLCI-B, which is considered more accurate according to vicarious validation data.