The In-Orbit Performance of SEVIRI From Observations of Mercury and Venus

Abstract

We investigated various aspects of the in-orbit performance of a Spinning Enhanced Visible Infra-Red Imager (SEVIRI) on Meteosat-10 (launch: 05 Jul 2012) and -11 (launch: 15 Jul 2015) with images, where Mercury or Venus stood close to earth. 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 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$0.66\pm 0.14$</tex-math></inline-formula> km at subsatellite point (SSP) with Meteosat-10 and longer by <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$1.44\pm 0.16$</tex-math></inline-formula> km at SSP with Meteosat-11. The tilt of the detector array against the equator is less than 0.0037 <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$^\circ$</tex-math></inline-formula> for SEVIRI on Metosat-10. The sampling with narrow channels in east–west direction is 3.0015 km, with a one-sigma uncertainty of 20 cm at SSP. 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 in the thermal infrared on a time scale of 1 h down to the 1% level. Hence, planets are a promising alternative to established methods of in-flight characterization and validation of imagers.