Performance of the GLAS Satellite Lidar Cloud and Aerosol Measurements

Launched in early 2003, the geoscience laser altimeter system (GLAS) on the Ice, Cloud and Land Elevation Satellite is the first polar orbiting satellite lidar and is intended for comprehensive earth science applications covering surface altimetry for ice sheets and vegetation and atmospheric profiling. The instrument design includes high performance observations of the distribution and optical scattering cross sections of atmospheric clouds and aerosol. The backscatter lidar operates at two wavelengths, 532 and 1064 nm. For the atmospheric cloud and aerosol measurements, the 532 nm channel was designed for ultra high efficiency with solid- state photon counting detectors and etalon filtering. Data processing algorithms were developed to calibrate and normalize the signals and produce global scale data products of the height distribution of cloud and aerosol layers and their optical depths and particulate scattering cross sections up to the limit of optical attenuation. Since the initial production of data products there has been extensive studies of the accuracy and limitation of the data products. Studies include the statistical analysis of results, quality checking surveys and inter-comparison to ground and airborne measurements. The paper concentrates on the effectiveness, results and limitations of the atmospheric lidar channel design and data product algorithms. Overall, given known instrument problems uncorrected before launch, the results validate the expectations of the lidar design.