Passive ocean color space-borne observations began in the late 1970s with the launch of the Coastal Zone Color Scanner space mission. An uninterrupted record of global ocean color data has been sustained since 1997. These passive observations have enabled a global view of the distribution of phytoplankton and marine primary productivity. However, these measurements are limited to clear sky, day-light, high Sun elevation angles, ice-free oceans and are exponentially weighted toward the ocean surface. Moreover, the processing of the ocean color images requires the knowledge of the atmospheric components (gases, air molecules and aerosols).
Lidar (Light Detection and Ranging) is a “laser radar” technique that has been used for a wide range of atmospheric and ocean applications. As an active remote sensing technique, it can overcome some of the above-mentioned limitations of passive observations. Despite several cases that demonstrated oceanic applications of ship-, air- and space-borne lidars, this tool has not received significant attention from the ocean color remote sensing community. Recently, it has regained interest from the ocean community as new studies used the lidar signal from the space-borne CALIOP/CALIPSO and ATLAS/Ice-Sat-2 instruments to estimate the ocean particulate backscatter and showed the feasibility of using both lidars to provide accurate estimates of the ocean color over the globe and in the polar regions (and over the water column for ATLAS). Thus, satellite lidars are a natural complement to passive ocean color radiometric remote sensing, operating under thin clouds, between holes in broken clouds, and in polar regions, providing vertical measurements both during day and night.
However, as those space-borne lidars are primarily dedicated to atmospheric and land measurements, several issues need to be considered for being able to optimally use them in oceanic applications. Among them, we propose to tackle the following issues: 1) Validation of CALIOP and ATLAS retrievals including inter-comparison of the results obtained with both retrievals and 2) Analysis of the limitations of the current space-borne lidars. The outcomes of this International Team work will help to define a scientific roadmap for a future dedicated space-borne oceanic profiling lidar.