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Instrument: AOLFL : Airborne Oceanographic Lidar Fluorosensor
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The NASA Airborned Oceanographic Lidar (AOL) Fluorosensor (AOLFL) is a
laser fluorospectrometer (and associated instruments) which is carried
onboard a NASA P-3B or NASA C-130 aircraft. The AOLFL measures a variety
of reflected and induced light properties, from which a number of
oceanographic surface water properties can be derived. These properties
include ocean color and phytoplankton pigment concentrations.
The primary AOLFL sensor is a dual wavelength laser fluorospectrometer.
This sensor transmits two laser wavelengths, one UV (355nm) and one green
(532nm) to the ocean surface from the aircraft. These laser frequencies
interact with the water molecules, causing a shift in the laser frequency.
This Raman shift of the 355nm and 532 nm laser radiation allows
normalization of other light measurements to compensate for changes in
water clarity. If biological organisms containing chlorophyll and/or
phycoerythrin are present in the water, the 532nm laser light is absorbed,
and reemitted as particular bands of fluorescence. These fluorescent
signals can be normalized to the water Raman signal, and have been shown
to agree well with shipboard measurements of the same pigments. The 355nm
laser radiation causes fluorescence of some of the dissolved organic
material in the water. The water Raman normalized of this dissolved
organic material is labeled CDOM (chromophoric dissolved organic matter).
The AOLFL also carries several spectrometers which measure the downwelling
sunlight incident on the top of the aircraft, and the reflected sunlight
from the ocean surface. From these measurements, various algorithms can
determine chlorophyll concentrations in the same manner as CZCS satellite.
The ability of the AOLFL sensors to make oceanographic optical component
measurements by both laser fluorescence techiques and by reflected spectra
techniques allows the validity of each technique to be tested.

[This sensor description was derived from the WWW pages of the Airborne
Oceanographic Lidar Laboratory, Observational Sciences Branch, Wallops
Flight Facility, NASA. See ]

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