CAL_LID_L2_VFM-ValStage1-V3-41 is the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) Lidar Level 2 Vertical Feature Mask (VFM), Validated Stage 1 Version 3-41 data product. Data for this product was collected using the CALIPSO Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) instrument. The version of this product was changed from 3-40 to 3-41 to account for a change in the operating system of the CALIPSO production cluster. This product describes the vertical and horizontal distribution of cloud and aerosol layers observed by the CALIPSO lidar. Cloud and aerosol discrimination for detected features is reported as a single value, the cloud-aerosol discrimination score (CAD_Score). CALIPSO was launched on April 28, 2006 to study the impact of clouds and aerosols on the Earth's radiation budget and climate. It flies in the international A-Train constellation for coincident Earth observations. The CALIPSO satellite comprises three instruments, CALIOP, Imaging Infrared Radiometer (IIR), and Wide Field Camera (WFC). CALIPSO is a joint satellite mission between NASA and the French Agency, CNES.