ATLID, ESA atmospheric backscatter LIDAR for the ESA EarthCARE mission

The ATmospheric LIDAR(Light Detection and Ranging), ATLID, is part of the payload of the Earth Cloud, Aerosol and Radiation Explorer (EarthCARE) mission, the sixth Earth Explorer Mission of the European Space Agency (ESA) Living Planet Programme (http://esamultimedia.esa.int/docs/SP_1279_1_EarthCARE.pdf). The EarthCARE payload consists of four instruments that will, in a synergetic manner, retrieve vertical profiles of clouds and aerosols, and the characteristics of the radiative and micro-physical properties, to determine flux gradients within the atmosphere and top of atmosphere radiance and flux. ATLID’s task is to provide vertical profiles of optically thin cloud and aerosol layers, as well as the altitude of cloud boundaries. With that purpose ATLIDemits < 35 ns duration laser pulses with 40 mJ energy in the UV, at a repetition rate of 51 Hz, while pointing in a near nadir direction along track of the satellite trajectory. The backscatter signal is collected by a 620 mm aperture telescope and is then filtered and redirected through the optics of the instrument focal plane assembly, in such a way that the atmospheric Mie and Rayleigh scatteringcontributions are separated and independently measured. After the manufacturing, qualification and delivery of all ATLIDunits, the optical and electrical integration has been conducted in parallel to assemble the Optical Flight Model (OFM) and the Electrical Flight Model (EFM). These two models, precursor to the instrument integration, allowed the early execution of the first performance and functional tests. Following these initial verification activities, and with the latest integration of the flight laser coolingsystem, the instrument assembly approaches its final flight configuration, paving the way for the ambient performance and environmental testcampaigns at full instrument level.