An airborne sensor for primary productivity and related parameters of coastal waters and large water bodies

Abstract

In this letter, details of an active airborne sensor designed primarily for remote sensing of ocean productivity and related parameters like bathymetry of coastal waters and large water bodies are presented. The sensor complements passive oceanographic sensors on satellites by its capability of detailed mesoscale, regional coverage. This is the first payload combining the sensing of bathymetry and fluorescence together in one package. The design of the sensor based on theory, the optics and electronics are described. An Nd:YAG laser with l000mJ at 1064nm and 450 mJ at 532 nm is used. Photomultipliers for the bathymetry channels and a position sensitive microchannel plate photomultiplier tube array for the fluorosensor channels form part of the detection system. RC coupling networks are used to separate the active signal from passive ambient light. The maximum depth resolvable with an accuracy of 0-5m is 948m at night in clear water and 66-3 m in moderately turbid water at a flight height of 150 m. The minimum detectable concentration of chlorophyll a is 01 mgm^-3. The auxiliary sensors required are also listed. The payload is in the 500 kg class and can be flown at an altitude of 150 m on an HS-748 aircraft modified for ‘ditching’ at sea.