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.

Meteorological research satellites on polar orbits observe occasionally the Moon, when it moves through their deep space view. Over the last few decades, a large data set built up, which allows to determine the lunar flux with unprecedented accuracy especially at wavelengths, for which the Earth’s atmosphere is opaque. We determined the disk-integrated brightness temperature of the Moon at 19 wavelengths between 4 and 15 µm and at five frequencies between 89 and 190 GHz for phase angles between -80° and +70° with HIRS, AMSU-B, MHS, and ATMS on NOAA and MetOp satellites

A major problem with calculating the uncertainties of measurements with weather satellites is the fact that a full characterisation and calibration of their instruments can only be carried out before launch. The Moon, however, makes at least some of these activities possible in flight as well by providing a reliable flux reference at a well-defined position. We used serendipitous observations of the Moon with AMSU-B and MHS on eight different satellites to measure pointing accuracy, spectral channels coregistration, and beamwidth with unprecedented accuracy in flight. In addition we compared these findings with the corresponding values obtained on ground. By analysing more than a hundred Moon intrusions in the deep space view we could determine the radiance of the Moon as a function of its phase angle and distance from the Sun. The difference in average brightness temperature of the lunar disk between perihelion and aphelion amounts to $4.4 \pm 2.3$ K at 183 GHz. We compare the measured brightness temperature of the Moon as a function of phase angle between $-85^{\circ}$ (waxing) and $+76^{\circ}$ (waning) with the predictions from two models and find that one of them reproduces the shape of this function very well.