EarthCARE-Simultaneous Space-Borne Observations of Clouds, Aerosols and Radiation

The Earth's radiation budget is primarily governed by clouds. An accurate quantification of their impact on radiation is however particularly difficult due to their high spatial and temporal variability and complex vertical structures. Satellite-based observations of the three-dimensional structure of clouds and aerosols collocated with top-of-the atmosphere radiation measurements are therefore highly desirable in order to directly link and verify the impact of clouds and aerosols on radiation on a global scale.

For this purpose, European, Canadian and Japanese scientists have jointly proposed the Earth Clouds, Aerosols and Radiation Explorer (EarthCARE) mission, which has been selected by the European Space Agency (ESA) and the Japan Aerospace Exploration Agency (JAXA) for implementation with a target launch date in the late 2013 timeframe.

EarthCARE embarks two active instruments and two passive instruments. A near-UV atmospheric backscatter lidar with a high-spectral resolution and polarisation receiver operating at 355nm for cloud and aerosol observations, a W-band (94 GHz) cloud-profiling radar with Doppler capability for cloud profiling and vertical motion observation, a multi-spectral imager (with 7 channels in the visible, near, short-wave and thermal infrared) for across-track cloud and aerosol measurements, and a three-view (fore, nadir, and aft) broad-band radiometer for top-of-the atmosphere radiance and flux estimates. The synergistic exploitation of the respective instrument data products will provide the vertical distribution of ice and liquid cloud profiles, heights and overlaps, vertical motion within clouds and precipitation. Furthermore, aerosol profiles will be measured. Collocated estimates of top-of-the atmosphere radiances will be provided by the broad-band radiometer's observations and will thus allow to link cloud, aerosol and radiation measurements.

The mission implementation is progressing on schedule for both the engineering and science preparation. An EarthCARE simulator (ECSIM) has been developed allowing end-to-end system and performance simulations, starting from atmospheric input scenes to simulated EarthCARE signals and retrieved geophysical data products. The simulator is undergoing further developments and is also being used for data processing algorithm developments. Intensive geophysical retrieval development activities are ongoing. The paper will provide an overview of the EarthCARE science objectives and development status.