Effect Of Spectral Response Function On Performance Of Ocean Colour Sensors

Abstract

Ocean remote sensing is a powerful tool to understand the properties of constituents of ocean water and it refers to the multi spectral measurements, in the visible range of wavelengths 400-700 nm, made from airborne or satellite. Solar radiation passes through atmosphere, reaches layers of water, gets scattered by the constituents, comes out as upwelling radiance, again goes through the atmosphere and finally it is sensed by ocean colour sensor. The sensor integrates the input spectrum as per its spectral response function and provides as a digital output. Retrieval process includes computation of top of the atmosphere spectral radiance using the digital count and spectral response function of sensor, estimation of atmospheric contributions using models, computation of water leaving radiance and estimation of physical parameters using bio-optical algorithms. During the above process, radiation goes through spectral changes which are dependent on constituents of atmosphere and water, season, location, time, viewing angle etc. Considering the significant contribution of atmospheric scattering in the sensor output, few spectral channels are incorporated in near infrared spectral region where the ocean upwelling radiance is very small. Recent systems have channels in short wave infrared also for better measurement of aerosol contributions. Sea viewing wide filed sensor, SeaWiFS, Ocean Colour Monitor, OCM-2 are some of the examples of ocean colour sensors. Estimation of Chlorophyll, identification of potential fishing zones, carbon cycle monitoring etc. are some of the operational applications for open ocean regions. newline