Abstract. The Earth Cloud Aerosol and Radiation Explorer (EarthCARE) is a satellite mission implemented by the European Space Agency (ESA) in cooperation with the Japan Aerospace Exploration Agency (JAXA) to measure global profiles of aerosols, clouds and precipitation properties together with radiative fluxes and derived heating rates. The data will be used in particular to evaluate the representation of clouds, aerosols, precipitation and associated radiative fluxes in weather forecasting and climate models. The satellite scientific payload consists of four instruments, a lidar, a radar, an imager and a broad-band radiometer. The measurements of these instruments are processed in the ground segment, which produces and distributes the science data products. The EarthCARE observational requirements are addressed. An overview is given of the space segment with a detailed description of the four science instruments. Furthermore, the elements of the Space Segment and Ground Segment that are relevant for the science data users are described.

Reliable, long term operation of high-power laser systems in the Earth orbit is not a straightforward task as the space environment entails various risks for optical surfaces and bulk materials. The increased operational risk is, among others, due to the presence of high energy radiation penetrating the metallic shielding of satellites and inducing absorption centers in the bulk of optical components, and vacuum exposure which can deteriorate coating performance. Comprehensive testing for analyzing high-energy radiation effects and mitigation procedures were performed on a set of frequency conversion crystals and are discussed in this paper. In addition to a general resistance to space environmental effects, the frequency conversion crystals were subjected to a comparative analysis on optimum third harmonic efficiency, starting from pulsed 1064 nm laser radiation, with the goal of exceeding a value of 30 %. Concomitant modeling supported the selection of crystal parameters and the definition of crystal dimensions.

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In this paper, a study of heat generation during UV laser-induced contamination (LIC) and potentially resulting subsequent thermal damage are presented. This becomes increasingly interesting when optics with delicate coatings are involved. During LIC, radiation can interact with outgassing molecules, both in the gas phase and at the surface, thus triggering chemical and photo-fixation reactions. This is a major hazard, in particular for laser units operating under vacuum conditions such as in space applications. The intense photon flux not only affects the contaminant deposition rate but also alters their chemical structure, which can increase their absorption coefficient. Over cumulative irradiation shots, these molecules formed deposits that increasingly absorb photons and produce heat as a by-product of de-excitation, eventually leading to thermal damage. One could better assess the risk of the latter with the knowledge of temperature during the contamination process. For this purpose, a thermoreflectance technique is used here to estimate the temperature variation from pulse to pulse during contamination deposition through the analysis of a temperature-dependent surface reflectance signal.

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