Concept & design of the backscatter lidar for EarthCARE

EarthCARE is one of the three candidate Earth Explorer Core Missions of the ESA Living Planet Programme. It will address the interaction and impact of clouds and aerosols on the Earth’s radiative budget. ATLID (ATmospheric LIDar), one of the four instruments of EarthCARE, shall determine vertical profiles of clouds and aerosols physical parameters (altitude, optical depth, backscatter ratio and depolarisation ratio) in synergy with other instruments. Operating in the UV range at 355 nm, ATLID provides atmospheric echoes with a vertical resolution of 100 m from ground to an altitude of 30 km. Thanks to a high spectral resolution filtering, the lidar is able to separate the relative contribution of aerosol (Mie) and molecular (Rayleigh) scattering, which gives access to aerosol optical depth. The following addresses the current instrument design as worked-out by Astrium during the EarthCARE Phase-A Study, which was was run in 2002-2003 under ESA contract. Besides the basic architecture trade-offs, the emphasis is put on some major technical and technological choices that were done to optimise the lidar performances and efficiency.