CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization)

CALIOP (Cloud-Aerosol Lidar with Orthogonal Polarization) is a two-wavelength polarization-sensitive lidar that measures vertical profiles of aerosol and cloud optical properties. It operates at 532 nm and 1064 nm, using elastic backscatter and depolarization ratio measurements at 532 nm to distinguish between ice crystals and liquid water droplets and to separate aerosol types.^[1][2]

CALIOP was built by Ball Aerospace and flown on the CALIPSO satellite (Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations), a joint NASA-CNES mission. CALIPSO launched on 28 April 2006 ^[3] and flew in formation with other Earth-observing satellites at approximately 685 km altitude ^[3]; WMO OSCAR records an altitude of 705 km ^[2]. Nominal science operations began in 2006 and continued through 31 July 2023, when the mission ended.^[4]

During its operational lifetime, CALIOP provided a multi-year global record of vertically resolved aerosol and cloud distributions from space, supporting research into aerosol radiative forcing, cloud microphysics, and atmospheric transport.^[1][5] Version 4 of the 532 nm nighttime calibration algorithm improved accuracy relative to earlier releases.^[5]