The Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP), an instrument on the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO), was operated as an atmospheric lidar system to study the impact of clouds and aerosols on the Earth’s radiation budget and climate. This paper discusses the receiver transient response of the CALIOP instrument, which is useful for getting a reliable attenuated backscatter profile from CALIOP data products. The noise tail effect (slow decaying rate) of PMT and broadening effect of the
low-pass filter are both considered in modeling of the receiver transient response. An analytical expression of the CALIOP transient response function was obtained by the least square fitting of lidar measurements from land surfaces.