Design And Development Of An Autocalibrating Radiometer For Deep Sea Biooptical Studies

Abstract

Abstrucr Measurements of light underwater are critical to research investigations involving a wide range of aquatic photo processes. Solid state detectors used in modern underwater irradiance meters are excellent detectors of bright sunlight in surface waters. However, these detectors are not sensitive enough to measure light over the intensity and temporal response range which are characteristic of the photic reactions of many marine organisms. Solar radiation below the epipelagic zone, lunar radiation and bioluminescence all exert a powerful influence on the population dynamics of the marine environment and therefore require accurate quantification. Photomultiplier tubes (PMTs), which have the sensitivity to measure such low intensities are not commonly used in radiometric instruments because they cannot match the accuracy and reliability of solid state detectors in field deployment. The Low Light Auto-Radiometer (LoLAR) was developed to extend the lower limit of contemporary underwater irradiance detectors. The system uses a PMT but circumvents the temperature sensitivity and poor stability of the tube with an internal calibration circuit.