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Particle and Optics Profiling System (POPS)

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tieuminh2510

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Particle and Optics Profiling System (POPS)

Bài gửi by tieuminh2510 on Tue Jun 24, 2008 3:52 pm


Particle and Optics Profiling System (POPS)

The Particle and Optics Profiling System (POPS) is an assembly of instruments designed to count and measure particles and to determine optical and environmental properties of water with depth. The heart of POPS is the Large Aggregate Profiling System (LAPS), designed and operated by our colleague, Dr. Ian Walsh.

LAPS consists of a video camera synched with a strobe light which flashes at predetermined intervals as the system is slowly lowered through the water. The light is channeled so that it illuminates only a narrow slab of water. The video camera faces the slab of light and records images of large particles in the water.

Your eyes record the same phenomenon when sunlight passes into a darkened room through a narrow slit in the curtains. You see hundreds of dust particles wafting through the slab of light, but the particles on either side of the slab are invisible. If you put a ruler next to the illuminated particles, you could measure their size. If you take a photograph of an area of known size, you can count the number and calculate the size of dust particles in the air. This is what we do with LAPS in seawater.

The video images generally show white dots, marine snow, in a dark sea. They are analyzed with software that counts the number of particles and determines their maximum and minimum dimensions if they are not circular. We use these data to estimate a volume and mass of the imaged particles, which range from 250 microns to several millimeters in size.

In addition to LAPS, POPS can carry a CTD, transmissometer, fluorometer, LISST, LSS and a-c meters. All except the CTD are optical instruments that measure either visibility in seawater or the sizes of particles.




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