Search

The Sentinel-2A and Sentinel-2B constellation is an Earth observation optical mission developed and operated by the European Space Agency in the frame of the Copernicus program of the European Commission. The novel observation capacity offered by the multispectral instruments (MSI) on-board Sentinel-2 mission provides a massive resource for the Earth observation community. The accurate radiometric calibration is a critical element of the success of the mission; therefore, in-orbit calibration and validation activities are conducted within the Sentinel-2 Mission Performance Centre. The database of the imaging multispectral instrument and tool for radiometric intercomparison and the ground measurements of the radiometric calibration network (RadCalNet) are used to perform the vicarious validation of the radiometry of the Level-1 products delivered to the users. The aims of this validation are to assess the quality of the data product, to monitor the evolution of the radiometry of both instruments, and to ensure that the products meet the mission requirement accuracy. This article outlines the vicarious methods—Rayleigh scattering, desert pseudoinvariant calibration sites, sensor-to-sensor intercalibration, and the ground reflectance-based approach—that are used for the Sentinel-2 radiometry validation. The validation results indicate good performance and stability of both sensors MSI-A and MSI-B and consistency up to ∼1% (∼2% for red-edge bands) between them. The results of the intercomparison with the in situ measurements from RadCalNet illustrate the relevance of such dataset for the vicarious validation activity.

With more than 4 TB of data acquired every day, the Sentinel 2 mission poses new challenges for quality control (QC). To support the QC operations of Sentinel 2, a dedicated tool has been developed for improved efficiency and traceability of analyses. This tool aims at helping visual inspection by human operators through automatic product retrieval, generation of quicklook images and production of quality indicators. The article describes the product sampling strategy used to select products suitable for quality control checks. Then we present the methodology used to generate quicklooks, compute relative and multi-spectral co-registration performance. The final step is the production of end-to-end service performance indicators. Lessons learnt from the first year of operation of this tool are presented regarding detected product anomalies and measured performance trends.

International audience; As part of the Copernicus programme of the European Commission (EC), the European Space Agency (ESA) operates the Sentinel-2 mission that acquires high spatial resolution optical imagery. The consistency of the image time series is ensured by some specific performance requirements such as multi-temporal spatial registration and radiometric stability, routinely monitored by the Sentinel-2 Mission Performance Centre (S2MPC). The products also provide a rich set of metadata and auxiliary data to support high-level processing activities. This presentation provides a description of the main level-1 products calibration and validation activities, performed by the S2MPC including several Expert Support Laboratories (ESL). Measured performances and analysed results show the good quality of the mission products both in terms of radiometry and geometry. The current performances for Sentinel-2A and Sentinel-2B are compared to mission product quality requirements.

Sentinel-2 is an Earth Observation optical mission developed and operated by the European Space Agency (ESA) in the frame of the Copernicus program of the European Commission. The mission consists on a MultiSpectral Instruments (MSI) on board a constellation of two satellites flying on the same orbit but phased at 180°: Sentinel-2A launched in June 2015 and Sentinel-2B launched in March 2017. It covers the Earth's land surfaces and inland and coastal waters every five days at the equator under the same viewing conditions with high spatial resolution and wide field of view. Accurate radiometric calibration is key to the success of the mission; therefore, in-orbit calibration and validation activities are conducted within the Sentinel-2 Mission Performance Centre (MPC), including a consortium of Expert Support Laboratories (ESL). The Database of Imaging Multispectral Instrument and Tool for Radiometric Intercomparison (DIMITRI) is used to perform the vicarious validation of Level-l products delivered to users. The aims of this validation are 1) to assess the quality of the data product at Level-1, 2) to monitor the evolution of the radiometry of both instruments and 3) to ensure that the products meet the mission requirement accuracy. Three vicarious methods are used, such as Rayleigh scattering, Desert Pseudo- Invariant Calibration Sites (PICS) and Sensor-to-Sensor intercalibration methods. Although the results indicate good stability and performance of both sensors MSI-A/B, a slight discrepancy between them of ~1 % over desert sites could be observed. Slight decrease of band B8A (865 nm) signal over Algeria-3 site has been detected since April 2017. This effect seems to be related to the impact of human and industry activities near the area. Radiometric performances and image quality of Sentinel-2 MSI-A/B level-1C products appear stable and meet the mission requirements.