On Space Launch Complex 2 at Vandenberg Air Force Base in California, the dual spacecraft CALIPSO and CloudSat, removed from its transport canister, is being mated in the mobile service tower with the second stage of its Boeing Delta II rocket for launch on April 21. CALIPSO stands for Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation. It will fly in combination with the CloudSat satellite to provide never-before-seen 3-D perspectives of how clouds and aerosols form, evolve, and affect weather and climate. CALIPSO and CloudSat will join three other satellites in orbit to enhance understanding of climate systems. Launch of CALIPSO/CloudSat is scheduled for April 21.