The EUMETSAT Polar System - Second Generation (EPS-SG) Visible/Infrared Imaging mission supports the optical imagery user needs for Numerical Weather Prediction (NWP), Nowcasting (NWC) and climate in the timeframe beyond 2020. The VII mission is fulfilled by the METimage instrument, to be flown onboard the Metop-SG-A satellite series. The instrument itself is a cross-purpose medium resolution, multi-spectral optical imager, measuring radiation emitted and reflected by the Earth from a low-altitude sun synchronous orbit with a swath width of 2700 km. Measurements will be made in 20 spectral channels ranging from 443 nm in the visible up to 13.345 μm in the thermal infrared at a spatial sampling distance of 500 m at nadir. This paper focuses on the Calibration and Validation (Cal/Val) activities planned for the METimage level 1B products to ensure that the calibrated and geolocated radiances meet the performance specifications for the lifetime of the mission. Such methods include cross-calibration with instruments on the same platform e.g. IASI-NG and Sentinel-5 measurements, inter-comparisons with other missions during simultaneous nadir overpasses, comparisons with ground based observations and lunar calibration. The level 1B product performance will be validated with respect to geometric, spectral, and radiometric requirements for all geographic regions including their seasonal variability. In particular the following specific activities are described: • Calibration verification • Validation of radiometry • Geometric verification • Image quality verification As the commissioning phase is limited in time, the products from METimage have to be confidence checked and validated with a concise focus on essential tests. The Cal/Val activities will extend to routine operations in order to ensure long term stability of the calibrated radiances and continually improve the calibration throughout the lifetime of the mission.

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P. Phillips, R. Bonsignori, D. Just, P. Schlüssel, F. Schmülling, and I. Zerfowski, "Calibration and validation of Level 1B radiances of the EUMETSAT polar system - second generation (EPS-SG) visible/infrared imager METimage," Proc. SPIE 10785, Sensors, Systems, and Next-Generation Satellites XXII, 1078512 (Presented at SPIE Remote Sensing: September 12, 2018; Published: 25 September 2018); https://doi.org/10.1117/12.2325545.