Sentinel-3 SLSTR Cal/Val activities for sea surface temperature measurements I. Tomažić (1), A. O’Carroll(1), G. Corlett (2), J.F. Piolle(3), P. Dash(4) , C. Donlon(5), D. Smith(6), S. Dransfeld(7), T. Hewison(1), A. Burini(1), F. Montagner (1) , V. Santacesaria(1) (1)EUMETSAT, Darmstadt, Germany (2)The University of Leicester, Leicester, United Kingdom (3)IFREMER, Plouzane, France (4)NOAA affiliate, US (5)ESA/ESTEC, Noordwijk, The Netherlands (6)RAL Space, Rutherford Appleton Laboratory, Harwell Oxford, UK (7)ESA/ESRIN, Frascati, Italy Introduction Copernicus Sentinel-3 (S-3) satellite carries the Sea and Land Surface Temperature Radiometer (SLSTR) and is a follow on of AATSR instrument. It is employing along track dual view scanning and two on-board calibration targets to obtain improved Sea Surface Temperature (SST) measurement. The first satellite in the series (S-3A) was successfully launched in February 2016 and the next one (S-3B) was launched in April 2018 to complete the first operational Sentinel-3 mission constellation. The next S-3 mission constellation (consisting from S-3C and S-3D) will ensure SLSTR data continuation for Copernicus program at least up to 2030. Sentinel-3A: 16th Feb 2016 Sentinel-3B: 25th Apr 2018 Instrument monitoring Geolocation verification Radiometric intercomparison: SLSTR vs IASI SST is the main parameter obtained from SLSTR instrument and one of the key parameters in global climate monitoring. Therefore, there is a very stringent requirement on producing SST retrievals from SLSTR. Absolute accuracy should be better than 0.3 K and with a temporal stability of 0.1 K/decade. To enable and confirm such a stringent requirements, set of Cal/Val activities are implemented for Sentinel-3/SLSTR mission both on Level-1 and Level-2 products. The main one on Level-1 encompasses monitoring of geolocation accuracy and radiometric inter-comparisons of SLSTR infrared channels with Infrared Atmospheric Sounding Interferometer (IASI), while on Level-2 it covers SST bias characterisation by comparison with in situ measurements and inter-satellite and inter-algorithm comparisons against Level-4 SST analysis. SST Bias Characterisation: Inter-satellite and inter-algorithm comparisons • Satellite comparison with OSI-SAF and CMEMS products • Analysing individual algorithms and instrument characteristics • Global and regional routine analysis • Daily, monthly plots, maps, time-series, histograms, .... • METIS: http://metis.eumetsat.int/sst/ SST Bias Characterisation: Comparisons with in-situ measurements • Copernicus Coriolis in situ service: drifters on GTS, OceanSITES (Pirata, GTMBA, ...) , Argo GDAC, GTSPP • Routine and automatic collocations (felyx) of SLSTR L1/L2 over in situ measurements and ship mounted radiometers • OSI-SAF Federated Activity SLSTR MDB: drifters, Argos, moored, radiometers •Current status: NRT@OPE and NTC@REPRO with SL L1 IR channels •Upcoming changes: NTC@OPE and NTC@REPRO with SL L1 all channels •Results presented for cycle 30: 07.04.2018-04.05.2018 •Results based on newly implemented Bayesian cloudmask SST L3 analysis Acknowledgements We would like to acknowledge The European Commission Copernicus Programme; The European Space Agency; Scientists and Industry throughout Europe. Special thanks to EUMETSAT, ESA and MPC/ESL collegues and to EUMETSAT S3-OPIT team. References EUMETSAT Sentinel-3 Mission Performance Implementation Plan (EMPIP), 2016, Issue v1C, pp.100 Sentinel-3 Calibration and Validation Plan, 2014, Eumetsat/ESA, S3-PL-ESA-SY-0265, Issue 2, pp. 235. Donlon, et al, The Global Monitoring for Environment and Security (GMES) Sentinel-3 mission, RSE, 120 (2012) Radiometric intercomparisons of AATSR and IASI, 2013, C. Whyte, D. Moore, J. Remedios Detector temperatures for IR channels from Jan 2017 to May 2018. Small discontinuities occur due to the scheduled decontamination or following an anomaly. The vertical lines indicate the start and end of each decontamination cycle. • Geolo