Radiometric and geometric calibration/validation of EPS-SG 3MI using natural targets

The Multi-View, Multi-Channel, Multi-Polarisation Imaging (3MI) instrument is a passive scanning radiometer dedicated to aerosol characterisation, air quality and numerical weather prediction, as well as climate monitoring and more generally characterisation of the microphysical properties of the atmosphere, including clouds. The 3MI mission has heritage from the POLarization and Directionality of the Earth's Reflectances (POLDER) on-board the ADEOS and PARASOL satellites. Compared to POLDER, 3MI has improved spatial coverage, higher spatial resolution, and an expanded spectral range with more spectral bands in the reflective part of the spectrum, all bands being polarised (except absorption bands). It is scheduled for launch on the EPS-SG platform in 2024. 3MI’s mission is to provide images of the Earth Top-Of-Atmosphere outgoing radiance for 12 different spectral bands (from 410nm to 2130nm), with 3 different polarisers (-60°, 0° and +60°), and 14 angles. The design consists of two optical heads (SWIR and VNIR) composed by a detector along with a filter and polariser rotating wheel and a wide field-of-view optics. The multi-view is achieved by several successive overlapping acquisitions of the same Earth-Atmosphere target under different angles thanks to the instrument large field of view. Using the experience acquired for the POLDER missions, CNES is cooperating with EUMETSAT and is providing the necessary analysis and expertise for the in-flight calibration and/or validation of several key parameters, both for geometric and radiometric aspects. Here we present the different methodologies that will be used to achieve that goal.