Chemistry Reference
In-Depth Information
The Imaging Airborne Laser Fluorosensor (named IALFS) as one of the
most complex and also quantitatively measuring remote sensing instru-
ments operated on an aircraft is an active laser-based sensor which sends
short (~20 ns) high energy UV laser pulses towards the water surface
(Hengstermann and Reuter 1990). This device is based on a XeCl excimer
laser with an output wavelength of 308 nm. The laser-induced scattering
and fluorescence is detected using a 20 cm telescope and spectrally sepa-
rated into 12 channels (Figure 4). The IALFS performs a conical scan of
the sea surface and thus provides information on the spatial distribution of
fluorescent and attenuating matter. At a platform altitude of 300 m this de-
vice has a swath width of app. 180 m. The fundamental principle of laser
fluorosensing of oil spills is given by the fact that crude oils and various
refined crude oil products can be photochemically excited by UV radiation
and classified by (remotely) analysing the spectral distribution of the re-
sulting fluorescence. Laser fluorosensors are still the only instruments that
can accomplish a remote classification of oil spills. Another feature of
these instruments is the estimation of oil thickness in the range between
app. 0.1 and 10 µm, depending on the type of oil and other parameters. In
addition, the laser fluorosensor may be used for hydrographical measure-
ments (Zielinski et al. 2000).
Fig. 4.
12-channel imaging airborne laser fluorosensor signature of spilled crude
oil (all data rectified). The channel #2 (344 nanometres) shows the suppression of
the laser-induced water Raman backscatter signal through the strongly absorbing
oil film. This information can be used for thickness estimation
