The project's objective is to gather and analyse datasets of normalized water-leaving radiance and aerosol optical thickness for cal/val of satellite ocean color sensors. Such datasets are needed to verify whether satellite retrievals of water-leaving radiance are within acceptable error limits and, eventually, adjust atmospheric correction schemes. The approach is to use a dedicated, specifically-designed, hand-held radiometer, the SIMBAD radiometer, onboard ships of opportunity (research vessels, merchant ships) travelling the world's oceans. The SIMBAD radiometer, built by the Laboratoire d'Optique Atmospherique (LOA) of the University of Lille, measures both variables in typical spectral bands of satellite ocean color sensors, namely 443, 560, 670, and 870 nm. To achieve adequate sampling, i.e. acquire data in a wide range of oceanic and atmospheric conditions, two complementary networks of ships/routes are operated, one by LOA (Responsible PI: Pierre-Yves Deschamps), the other by the Scripps Institution of Oceanography (SIO) of the University of California San Diego (Responsible PI: Robert Frouin). The SIO network is supported by NASA under the SIMBIOS initiative, and the LOA network is supported by several French organizations including CNES. The SIMBAD data acquired by both networks, after proper quality-control and processing, are made available to the SIMBIOS Project Office. Information about the LOA network is available at: http://www-loa.univ-lille1.fr/~simbad/