To validate MERIS remote sensing reflectances at sea surface for case 1 waters in-situ measurements were taken during several ship cruises across the Atlantic. The in-situ data sets were collected with a system of three TriOS-RAMES hyperspectral spectroradiometers, measuring above-water upwelling radiance, downwelling irradiance and sky radiance. From these data sets, the water leaving remote sensing reflectance was calculated. Results will help to evaluate the atmospheric correction applied to MERIS case 1 data and will be used to interpret the comparisons of in-situ measured chl a and MERIS algal-1 chl a.