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The first two models of the Sea and Land Surface Temperature Radiometers (SLSTR) for the European Copernicus Sentinel-3 missions were tested prior to launch at the Rutherford Appleton Laboratory space instrument calibration facility. The pre-launch tests provide an essential reference that ensures that the flight data of SLSTR are calibrated to the same standards needed for surface temperature measurements and to those used by shipborne radiometers for Fiducial Reference Measurement (FRM). The radiometric calibrations of the thermal infrared channels were validated against accurate and traceable reference BB sources under flight representative thermal vacuum environment. Measurements were performed in both earth views for source temperatures covering the main operating range, for different instrument configurations and for the full field-of-view of the instruments. The data were used to derive non-linearity curves to be used in the level-1 processing. All results showed that the measured brightness temperatures and radiometric noise agreed within the requirements for the mission. An inconsistency that particularly affected SLSTR-A was observed which has been attributed to an internal stray light error. A correction for the stray light has been proposed to reduce the error. The internal stray light error was reduced for SLSTR-B by replacing the coating on the main aperture stop. We present a description of the test methodology and the key results.

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ABTRACTMeteosat Second Generation (MSG) is a series of 3 (possibly 4) geostationary satellites developed and procured by the European Space Agency (ESA) on behalf of the European Organisation for the Exploitation of Meteorological Satellites (EUMETSAT). The first satellite (MSG-1) was launched on 29 th August, 2002 by an Ariane 5 rocket. After the LEOP and the drift to the commissioning longitude, the satellite was positioned above the Atlantic Ocean at 10.5 o W (longitude) with a 1.9 o orbital inclination. The prime contractor of MSG satellite series is Alcatel Space Industries (France) and the Imaging Radiometer SEVIRI is procured under the responsability of Astrium SAS (France). The MSG-1 satellite commissioning is performed by EUMETSAT with the support of ESA and industry. MSG-1 commissioning started on 25 th September 2002. This paper addresses the results of the SEVIRI functionality tests performed as part of the MSG-1 commissioning and describes the radiometric and imaging performances of the main optical payload SEVIRI, including the image quality after its rectification and calibration. The performance results presented here are based on an offline analysis of a limited subset of the large amount of SEVIRI data obtained during the MSG-1 commissioning tests.

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