The Ocean Land Colour Imager (OLCI) for the Sentinel 3 GMES Mission: Status and first test results

摘要

Ocean colour sensors are designed to retrieve the spectral distribution of upwelling radiance just above the sea surface (the water-leaving radiance) that is then used to estimate a number of geophysical parameters through the application of specific bio-optical algorithms. Atmospheric correction for ocean colour data is challenging (IOCCG, 2010) as only about 4% of the radiation measured by a satellite instrument originates from the water surface and sensors require high signal to noise ratio (SNR), particularly for the 'blue' bands (～400 run). Ocean colour instrument design must therefore incorporate extremely sensitive and stable radiometry, dedicated on-board calibration and a large number of spectral channels. The Ocean & Land Colour Imager (OLCI) is a high accuracy visible near-infrared optical payload for the Sentinel 3 component of the GMES mission, to provide climatological data continuity with the previous ESA Envisat missions. OLCI is based on the successful opto-mechanical and imaging design of ENVISAT MERIS. The instrument is a quasi-autonomous, self contained, push-broom imaging spectrometer and incorporates the following significant improvements when compared to MERIS, i.e., more spectral bands, 300 m full resolution over land and ocean, and 2-daily coverage.