This view is the very first image acquired by POLDER onboard ADEOS over
France on September 16th 1996.
It is a blue, green and red color composite of POLDER measurements at 443 nm, 670 nm and 865 nm.
Marked differences appear between the clouds (in white) and different types of surfaces: vegetation in red, soil in brown and yellow, sea in dark blue. The bright spot in the Mediterranean sea, West of Sardaigne, is the sunglint pattern.
More than 15000 such images are taken every day by POLDER on ADEOS providing a daily global coverage of the Earth in eight spectral channels of the visible and near infrared spectrum.
On the conventional image (left), marked differences appear between the clouds (in white) and different types of surfaces: vegetation in red, soil in brown and yellow, sea in dark blue. The bright spot in the Mediterranean Sea, west of the island of Sardinia, is the sunglint pattern.
On the polarized image (right) the color blue prevails and the
contours can hardly be recognized. This is because the polarized light
mainly results from scattering in the atmosphere which increases at shorter
The clouds still appear in grey or white and the sunglint spot in the Mediterranean Sea corresponds to a strong polarized signal.
The additional information provided by these original polarized measurements allows a better characterization of the atmospheric contribution to the signal measured at the top of the atmosphere, and thus an improvement in the determination of both surface and cloud parameters of interest.
An examination of the same area followed from one image to the other shows large variations in intensity. In the Mediterranean Sea a bright spot corresponding to sunglint appears west of Corsica and moves southwards before disappearing near the African coast (images 1 to 3).
Owing to its wide field of view POLDER can take images of a single target successively from different viewing angles. This unique capacity allows the directional properties of the radiation reflected by land surfaces and clouds to be characterized and studied. See CNES news.
Earth Observation Research Center
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Last Update: 02 October 1996