PARASOL is one of a constellation of satellites, which also includes Aqua, CALIPSO, and Aura, that fly in similar orbits around the Earth studying various processes on the land and ocean, and in the atmosphere. PARASOL, a CNES (French space agency) mission, is specifically designed to measure the direction and polarization of light reflected from areas of land observed by the lidar carried by CALIPSO. It was launched on 18 December 2004 by an Ariane-5G rocket.