Active–passive airborne ocean color measurement 1: Instrumentation

Abstract

A multichannel lidar fluorosensor spectrometer has been configured to function concurrently as a passive spectroradiometer for measuring upwelling ocean color radiance. To accommodate passive detection, the NASA airborne oceanographic lidar (AOL) fluorosensor was modified to electronically integrate, digitize, and record the solar-induced direct current output available from the photomultiplier detectors of the lidar spectrometer along with the previously reported laser-induced fluorescence (LIF) and water Raman backscatter signals. In addition to a detailed theoretical analysis of each subsystem, exhaustive test and evaluation experiments were conducted with the dual-mode active and passive AOL system using (a) ground test targets and a calibration hemisphere and (b) field trials flown in the New York Bight region of the Atlantic Ocean. It is shown that very little interaction occurs between the active and passive modes. The justification for a dual-mode active-passive instrument is briefly presented.