As part of the Copernicus program of the European Commission, the European Space Agency (ESA) developed and operated the Sentinel-2 constellation (S2A, S2B); and in cooperation with the EUMETSAT, they are operating the Sentinel-3 constellation (S3A, S3B). Both are Earth Observation optical missions, where the MultiSpectral Instruments (MSI) is carried on board Sentinel-2 mission and the Ocean and Land Colour Instrument (OLCI) and Sea Land Surface Temperature Radiometer (SLSTR) are on board Sentinel-3 mission. In the framework of the Copernicus Optical Mission Performance Cluster (OPT-MPC), we use the Database for Imaging Multispectral Instruments and Tools for Radiometric Inter-comparison (DIMITRI) to perform the radiometry intercomparison of the Level-1 products. The aims of this presentation are 1) to assess the quality of the data product; 2) to monitor the temporal evolution of the radiometry of the instruments MSI, OLCI and SLSTR for both unites A and B.The results of the intercomparison show a good stability of the sensors, although SLSTR-A & B show slight positive trend. MSI and SLST pairs A & B show good agreement better than 1% while OLCI constellation displays slight discrepancy up to 2-3%. While MSI-A, MSI-B, OLCI-B gain coefficients are within the missions’ requirements, OLCI-A, SLSTR-A and SLSTR-B ones are slightly higher of the mission requirements.

The Copernicus Sentinel-2 Global Reference Image (GRI) was originally designed with the main goal of being used by the Ground Segment Level-1 processor to geometrically refine the Sentinel-2 data. The usage of the GRI has enabled a real improvement of the Sentinel-2 data geometric performance. Indeed, both absolute geolocation and relative (multi-temporal) performances have significantly improved and meet the requirements.It is expected that the use of the GRI could be then beneficial to other missions than Sentinel-2. In this framework and driven by user’s needs, ESA decided to freely give access to the scientific community to the entire GRI. Moreover, in order to facilitate the use of the GRI, a set of Level-1C images and a database of Ground Control Points (Level-1B and Level-1C geometries) have been derived from the Level-1B Sentinel-2 GRI. This paper recalls the characteristics of this Calibration/Validation GRI databases as well as the validations performed.

The Copernicus Sentinel-2 satellite mission, with its Sentinel-2A and Sentinel-2B units, offers since several years now a massive quantitative and qualitative resource for the Earth Observation community. Since the launch of Sentinel-2A in 2015, and Sentinel-2B in 2017, many lessons have been learnt leading to continuous improvements of the radiometric and the geometric performances. However, the current archive is composed of heterogenous processing baselines with inconsistent product formats and uneven data quality, which limits its use for multi-temporal monitoring applications.To overcome this limitation, the Copernicus program has undertaken a complete reprocessing with the latest processing baseline (05.00). It concerns the L1C (Top-Of-Atmosphere reflectance) and L2A (Surface Reflectance) products. This paper recalls the features of Collection-1 products and gives an overview of the first validation results.

Sen2Cor is the atmospheric correction processor selected by ESA for operational, systematic processing of Copernicus Sentinel-2 mission data. It is used for generating the Level-2A products distributed to users by the Copernicus SciHub. Accurate atmospheric correction of Sentinel-2 data and knowledge of its uncertainties are preconditions for high quality downstream applications. In this work we present the comparison of Sentinel-2 Bottom-of-Atmosphere products with measurements of surface reflectance on ground. Source of reference measurements are both surface reflectance data from RadCalNet and from dedicated field campaigns. The analysis shows, that the uncertainty of SR-retrieval with Sen2Cor is better than about 7% for bright surfaces and about 17% for darker. In addition to this performance evaluation, the data are also applied to compare the use of reference data coming from permanent operating bright RadCalNet sites and from ad-hoc field campaigns at darker sites.

The Sentinel-2 constellation consists on two unites MSI-A & MSI-B, which are an Earth Observation optical mission developed and operated by the European Space Agency (ESA) in the framework of the Copernicus programme of the European Commission. The Sentinel-2 Mission Performance Centre (MPC) is responsible of the calibration, validation, and image quality of the user product. The inter-unit consistency of the radiometry measurements is critical for the mission as more sentinel-2 platforms are planned in the future. In order to assess the validity and temporal stability of the radiometry measurements, two independent vicarious calibration (Desert PICS and Angular-Matchups) methods for EO optical sensors have been applied over land targets. We use DIMITRI (Database for Imaging Multispectral Instruments and Tools for Radiometric Intercomparison) toolbox. The results of the validation show an excellent image quality and stable radiometric performance, which meets the mission requirements target. Nonetheless systematic radiometric biases of 1.1 % across the VNIR spectrum are found with high confidence.

The more high-quality Earth Observation (EO) data are available to users, the more their potential applications increase in number. This is boosting the request for EO data already processed to a minimum set of requirements and needing limited pre-processing steps in order to be used, also when distributed by different EO data providers. The Analysis Ready Data (ARD) concept has been conceived, and a large effort is being made at international levels in order to converge towards a common definition. In this context, the Committee on Earth Observation Satellites (CEOS), with its member Agencies and institution, has worked to define the CEOS ARD for Land (CARD4L) specifications. The Copernicus Sentinel-2 Level-2A product has undergone a self-assessment process performed by the European Space Agency (ESA) aimed at preliminary assessing its compliance status with respect to the CARD4L specifications for optical surface reflectance.

The Sentinel-2 mission is a key element of the Copernicus Earth monitoring program of the European Union. The mission is currently composed of two satellites and provides a continuous observation of land and coastal areas at high spatial resolution and with a revisit time of 5 days at the equator. The geometric uncertainty of the Sentinel-2 product is a critical contributor to the performance of the mission. We present the approach used to calibrate the geometric performance of Sentinel-2 data and latest activities, especially related to the co-registration with the Global Reference Image (GRI). Generation of the GRI, coregistration algorithm, called geometric refinement, and preliminary results are presented.

Reliable cloud screening remains a critical issue for the analysis of optical imagery. In this work we present the recent evolutions of the Cloud Screening and Scene Classification module of Sen2Cor processor for the Copernicus Sentinel-2 mission. In addition to a Level-2A surface reflectance product, Sen2Cor provides a Scene Classification (SCL) map divided into 11 classes. The information provided by this map is of great interest for automated processing chains. It can be used to mask out clouds, cloud shadow, water, snow/ice from the Sentinel-2 imagery, so that downstream processing can be performed on clear land pixels, suitable for time-series analysis and quantitative remote sensing. The performance and limitations of the current algorithm are recalled. The updates aimed at improving the overall accuracy of the cloud screening are described (efficient topographic shadows computation, mitigation of false snow detection in clouds and mitigation of false clouds detection on bright targets). Preliminary results based on a Sen2Cor prototype are discussed.

Sen2Cor is a Level-2A processor designed to correct Sentinel-2 Level-1C products from the effects of the atmosphere in order to deliver a Level-2A surface reflectance product. ESA has been using Sen2Cor for systematic Level-2A processing of Sentinel-2 acquisitions over Europe since June 2017. It has since then been successfully integrated into Sentinel-2 ground segment (PDGS) with a global production over the World started in December 2018. In this manuscript, the Level-2A product and algorithm are presented. The performance of this operational Level-2A product is described in terms of cloud screening accuracy and atmospheric correction accuracy. Finally, the on-going parallel developments aimed at improving the product quality at global scale in terms of cloud screening and atmospheric correction are discussed.

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.

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.