Measurements of the atmospheric aerosol optical thickness were made during the 1977 EOMET cruise across the Atlantic Ocean and the Mediterranean Sea. These data were obtained at the same time as NOAA 5 and GOES visible radiance measurements in the vicinity of the ship. Linear relationships between the upwelling radiance and the aerosol optical thickness were found for each satellite, confirming earlier Landsat results. Differences in the relationships for each satellite are attributed to differences in the radiometric calibrations of the satellite sensors. Abstract Measurements of the atmospheric aerosol optical thickness were made during the 1977 EOMET cruise across the Atlantic Ocean and the Mediterranean Sea. These data were obtained at the same time as NOAA 5 and GOES visible radiance measurements in the vicinity of the ship. Linear relationships between the upwelling radiance and the aerosol optical thickness were found for each satellite, confirming earlier Landsat results. Differences in the relationships for each satellite are attributed to differences in the radiometric calibrations of the satellite sensors.