The In-orbit Performance of SEVIRI From Observations of Mercury and Venus
We investigated various aspects of the in-orbit performance of SEVIRI on Meteosat-10 (launch: 05 Jul 2012) and -11 (launch: 15 Jul 2015) with images, where Mercury or Venus appeared in a corner. These objects are of similar or smaller size than the instantaneous field of view, and therefore they are well suited for checks of geometric requirements. From comparing the position of Venus in different channels we conclude that the North-South distance between the two focal planes is shorter than the nominal value by 0.66 km at SSP (Sub-Satellite Point) with Meteosat-10 and longer by 1.44 km at SSP with Meteosat-11. The tilt of the detector array against the equator is less than 0.0037° for SEVIRI on Metosat-10. The sampling with narrow channels is 3.0016 km, with a one-sigma uncertainty of 30 cm at sub-satellite point. The tests we carried out to check the geometric performance of the instrument confirmed that SEVIRI is compliant with the requirements. The Point Spread Function as determined from the image of a planet agrees well with the expectations based on its combination with the finite impulse response. Finally we determined the stability of the calibration coefficients from the counts obtained on the planetary targets and found the reproducibility of the measurements of planetary fluxes similar to those of vicarious calibration targets. Hence planets are a promising alternative to established methods of in-flight characterisation and validation of imagers.