Instrument: PIC Sensor

Description from Bishop et al. (2022) (doi: 10.3389/frsen.2022.837938)

PIC Sensor Concept: The sensor concept has been described by Guay and Bishop (2002) (doi: 10.1016/s0967-0637(01)00049-8) and Bishop (2009) (doi: 10.5670/oceanog.2009.48). The first profiling sensor was a modified version of an analog WETLabs C-Star 25 cm pathlength transmissometer. A 660-nm laser replaced the LED source, and a cell with high crossing efficiency polarizers (630–700 nm, Polarcor, Corning) was inserted into the water path length of the instrument. At the source end, the polarizer is aligned with the plane of polarization of the laser; on the receiver end, the polarizer is crossed, thus minimizing the detection of the primary beam. The sensor thus detects the photon yield resulting from the interaction of polarized laser light with birefringent particles in the beam. The first full water column profiles of the first sensor (PIC001) took place in 2003 in the North Atlantic (Bishop, 2009). This sensor was stabilized in 2006 by replacing the cell with body-mounted polarizers.

Over many iterations of the basic design and multiple sea trials, it was demonstrated in 2013 that multiple PIC sensors yielded identical results and exceeded the performance of PIC001.