ARGANS main ESA-funded activities will include the evaluation of new ocean colour products within the ESA DUE GlobColour project.

1. Basic background: ESA has one mission aboard ENVISAT: the Medium Resolution Imaging Spectrometer Instrument (MERIS), NASA has three missions in orbit to assess ocean biological processes by measuring the colour of the sea, the Sea-viewing Wide Field of view Sensor (SeaWiFS) and two flight models of the Moderate Imaging Spectrometer (MODIS) on the Terra and Aqua Earth Observing System (EOS) missions. CNES has now launched a new POLDER on board Parasol. These ocean colour missions have been developed to answer many of the most basic questions of how the ocean biosphere operates, such as what is the role of climate change on the oceans, or how do anthropogenic processes (in particular increasing atmospheric CO2) influence the ocean biosphere? The numerous present and future ocean colour missions make it hard to decide which is the appropriate data set to work with. Should one use imagery from one satellite, or maybe composite imagery from MODIS and MERIS sensors? Ultimately, better ocean colour data products will come from the merging of different data sets, and there are there are several classes of users who could benefit from merged data sets and build data system such as researchers and students.

MERIS Calibration and Validation project: There is a need, in remote sensing to calibrate and independently validate the instruments onboard the satellites. Quality in situ data is required to assess how the instrument is performing and to judge what adjustments may be necessary. This is validation. Validation is the process of matching in situ datapoints with spatially and temporally coincident satellite measurements. The more reliable data available the better, and the ideal situation is to have a large, standardised database of in situ measurements from all over the world, that can be used to validate ocean colour measurements from the ESA MERIS instrument onboard Envisat. The task of ARGANS is to collate as much in situ data from research institutes all over the world and to build and maintain a database of coincident in situ data with their counterpart MERIS product. ACRI-ST will use the database for validation. Moreover, ARGANS will work closely with ACRI-ST to decide upon the algorithms and techniques for carrying out such validation. ARGANS is also tasked with keeping up to date the reference model documents that support this work, and to aid in algorithm improvements where necessary.