Simulations for optimal payload tilt to avoid sunglint in IRS-P4 Ocean Colour Monitor (OCM ) data around the Indian subcontinent

Ocean Colour Monitor (OCM) payload, onboard Indian Remote Sensing Satellite (IRS)-P4, detects the water constituents from the spectrum of solar radiation backscattered from the ocean waters. The radiation received by the sensor is contaminated by the specularly reflected solar radiation from the water surface. This specularly reflected radiation, called sunglint, contains no information on the water constituents, as it has not entered into the seawater and interacted with it. The intensity and spread of sunglint is determined by the solar illumination and sensor viewing directions and the sea surface roughness caused by the wind. For the accurate estimation of oceanic constituents, it is essential to minimize the sunglint in the detected radiances (preferably below ～2-3%). In this work, sunglint simulations were computed for the instrument specifications of OCM and the optimal sensor viewing tilt angle identified for each month for the oceans around India.