It is impossible to remotely (from satellite) observe ocean colour through cloud, and time on research vessels is limited and expensive. Mounting colour sensors on aircraft provides a means of avoiding some of the cloud and covering larger areas in shorter time periods and the airborne sensors, such as CASI, provide a valuable link between the sea surface measurements and satellite data (e.g. SeaWiFS and MERIS). Another method being trialled is by the installation of above-water radiometers on the ferries, such as the Ulysses, crossing from Dublin-Holyhead, providing regular temporal coverage, though restricted spatial coverage of the central Irish Sea. All methods provide measurements of surface colour signatures relating to water quality parameters, but need to be cross validated with in situ data to enable the derivation of algorithms and as validation for the atmospheric correction. This project proposes a combined approach using airborne, above-water and satellite radiometry to study the biogeochemical variability across the Irish Sea with in situ sampling providing validation data.