A Simple Method to Minimize Orientation Effects in a Profiling Radiometer

Abstract

Marine optical parameters required for ocean color satellite applications must be measured with high accuracy and errors within the permissible limits. These stringent requirements demand careful measurements of optical parameters. Though the free-fall radiometer is found to be a better option for measuring underwater light parameters as it avoids the effects of ship shadow and is easy to operate, the measurements demand profiling the radiometer vertical in water with minimum tilt. Here we present the results of our observations on the tilts of the radiometer from the measurements in the Arabian Sea. Since there is hardly any study carried-out on the tilt of the profiling radiometer, the result of this study will help in the better design of such marine instruments. The tilt of the radiometer near the surface of the water is attributed to the mode of deployment and environment parameters, while the tilt at depth of the water is influenced by the density variations of the water. Here we also demonstrate a method of deploying the instrument that minimizes the tilt of the instrument at the surface layer of the water.

Keywords:

• Profiling radiometer
• tilt
• orientation
• optical data
• free-falling body

Acknowledgements

The work was carried out under the project on bio-optical measurements of the coastal waters, funded under SATCORE program of Indian National Centre for Ocean Information Services, India. The authors are indebted to the Ministry of Earth Sciences for providing the research vessel, ORV Sagar Kanya. Thanks to Amanda Fernandes for help in preparing this manuscript.

NIO contribution number 5169.