Influence of aerosols on off-axis laser detection capabilities
conference paper
The radiation coming from a laser which operates in the coastal zone can be detected not only when a detector is placed
in front of the laser beam but also when it is located outside the main beam direction. The reason is that in a real
detection scheme the power collected by a detector not only comes from direct radiation but also from other radiation
sources, like port scattering, aerosol scattering and background radiation. Their relative contributions depend on many
factors, i.e. laser features, collecting optics features, meteorological conditions, etc. An important contributor is aerosol
scattering and its intensity depends on the aerosol composition and particle density. It was found that more humid
conditions cause a decrease in the direct radiation and an increase in the diffuse component. This effect depends on the
contribution of hygroscopic and non-hygroscopic aerosols. In the marine-continental atmosphere, represented by a
mixture of sea-salts (SSA), anthropogenic salts (WS) and organic carbon (OC), a change in relative humidity from 80%
to 95% can change the result for the predicted irradiance level on the sensor by more than a factor of three. Dust-like
(DL) particles produce much stronger scatter irradiance than other aerosol types, independently of the off-axis distance.
in front of the laser beam but also when it is located outside the main beam direction. The reason is that in a real
detection scheme the power collected by a detector not only comes from direct radiation but also from other radiation
sources, like port scattering, aerosol scattering and background radiation. Their relative contributions depend on many
factors, i.e. laser features, collecting optics features, meteorological conditions, etc. An important contributor is aerosol
scattering and its intensity depends on the aerosol composition and particle density. It was found that more humid
conditions cause a decrease in the direct radiation and an increase in the diffuse component. This effect depends on the
contribution of hygroscopic and non-hygroscopic aerosols. In the marine-continental atmosphere, represented by a
mixture of sea-salts (SSA), anthropogenic salts (WS) and organic carbon (OC), a change in relative humidity from 80%
to 95% can change the result for the predicted irradiance level on the sensor by more than a factor of three. Dust-like
(DL) particles produce much stronger scatter irradiance than other aerosol types, independently of the off-axis distance.
Topics
TNO Identifier
242077
Publisher
SPIE
Article nr.
74630E
Source title
Atmospheric Optics: Models, Measurements, and Target-in-the-Loop Propagation III, 3 August 2009, San Diego, CA, USA
Editor(s)
Hammel, S.M.
Eijk, A.M.J. van
Vorontsov, M.A.
Eijk, A.M.J. van
Vorontsov, M.A.
Place of publication
Bellingham, WA
Files
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