CloudSat and CALIPSO within the A-Train: Ten years of actively observing the Earth system

One of the most successful demonstrations of an integrated approach to observe Earth 16 from multiple perspectives is the A-Train satellite constellation (e.g. Stephens et al., 17 2002). The science enabled by this constellation flourished with the introduction of 18 the two active sensors carried by the NASA CloudSat and the NASA/CNES Cloud19 Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) satellites that were launched together on April 28th 20 , 2006. These two missions have provided a 21 10-year demonstration of coordinated formation flying that made it possible to 22 develop integrated products and that offered new insights on key atmospheric 23 processes. The progress achieved over this decade of observations, summarized in this 24 paper, clearly demonstrate the fundamental importance of the vertical structure of 25 clouds and aerosol for understanding the influences of the larger scale atmospheric 26 circulation on aerosol, the hydrological cycle, the cloud-scale physics and on the 27 formation of the major storm systems of Earth. The research also underscored 28 inherent ambiguities in radiance data in describing cloud properties and how these 29 active systems have greatly enhanced passive observation. It is now clear that 30 monitoring the vertical structure of clouds and aerosol is essential and a climate data # Corresponding author, email [e-mail], Jet Propulsion Laboratory, California Institute of Technology, 4800 Oak Grove Drive Pasadena, CA 91101 2 31 record is now being constructed. These pioneering efforts are to be continued with 32 EarthCARE mission planned for launch in 2019.