The European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) are co-operating to develop
as part of ESA’s Living Planet Programme, the third Earth Explorer Core Mission, EarthCARE, with the ojective of
improving the understanding of the processes involving clouds, aerosols and radiation in the Earth’s atmosphere.
EarthCARE payload consists of two active and two passive instruments: an ATmospheric LIDar (ATLID), a Cloud
Profiling Radar (CPR), a Multi-Spectral Imager (MSI) and a Broad-Band Radiometer (BBR). The four instruments data
are processed individually and in a synergetic manner to produce a large range of products, which include vertical
profiles of aerosols, liquid water and ice, observations of cloud distribution and vertical motion within clouds, and will
allow the retrieval of profiles of atmospheric radiative heating and cooling. MSI is a compact instrument with a 150 km
swath providing 500 m pixel data in seven channels, whose retrieved data will give context to the active instrument
measurements, as well as providing cloud and aerosol information. BBR measures reflected solar and emitted thermal
radiation from the scene. Operating in the UV range at 355 nm, ATLID provides atmospheric echoes from ground to an
altitude of 40 km. Thanks to a high spectral resolution filtering, the lidar is able to separate the relative contribution of
aerosol and molecular scattering, which gives access to aerosol optical depth. Co-polarised and cross-polarised
components of the Mie scattering contribution are measured on dedicated channels. This paper will provide a description
of the optical payload implementation, the design and characterisation of the instruments.