Artist's concept shows CALIPSO in orbit. CALIPSO (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations) is a joint NASA and CNES environmental satellite which was launched on April 28, 2006. Passive and active remote sensing Instruments on board the CALIPSO satellite monitor aerosols and clouds 24 hours a day. CALIPSO is part of the "A Train", flying in formation with several other satellites (Aqua, Aura and CloudSat). Three instruments: Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) - a lidar that provides high-resolution vertical profiles of aerosols and clouds. Wide Field Camera (WFC) - a modified version of the commercial off-the-shelf Ball Aerospace CT-633 star tracker camera. It was selected to match band 1 of the MODIS instrument on the Aqua satellite. Imaging Infrared Radiometer (IIR) - used to detect cirrus cloud emissivity and particle size. The CALIOP laser beam is aligned with the center of the IIR image to optimize joint CALIOP/IIR observations. Imaging Infrared Radiometer (IIR) - used to detect cirrus cloud emissivity and particle size. The CALIOP laser beam is aligned with the center of the IIR image to optimize joint CALIOP/IIR observations.