Feb. 21, 2003
First natural- and polarized-light images acquired by POLDER 2
The POLDER 2 instrument on board the ADEOS II satellite acquires images in eight spectral bands, from the visible to the near-infrared, in natural and polarized light.
These two images were acquired on 1 February 2003 over the Iberian Peninsula and North Africa in natural light (left) and polarized light (right). Each image is a colour composite of three spectral bands at 443 nm (blue), 670 nm (green) and 865 nm (red). In the natural-light image we can clearly distinguish clouds in white, the sea in dark blue and different types of surface features: vegetation in red and bare soils in brown or yellow.
The polarized-light images are more original. Blue dominates because the main source of polarized light is more efficient scattering of light by air molecules at short wavelengths. The degree to which light scattered by the atmosphere is polarized depends on the angle between the line of sight and solar illumination. This property of light is what allows us to see a rainbow, which is the result of the scattering of light by water droplets, and makes it possible to tell whether cloud tops contain ice crystals or water droplets.
These images also show that the Earth's surface only polarizes light to a very small extent, which means that polarized brightnesses can be used to characterize the atmosphere in very fine detail and determine the nature of aerosols.
First sequences of images over Europe and Africa
The POLDER 2 on board the ADEOS II acquires images in eight spectral bands, from the visible to the near-infrared, and from different viewing angles. These first light sequences of images (top down and left to right) were acquired on 1 February 2003 over Western Europe and North Africa. Each image is a color composite of three spectral bands at 443 nm (blue), 670 nm (green) and 865 nm (red). They clearly distinguish clouds in white, the sea in dark blue and different types of surface features: vegetation in red and bare soils in brown or yellow.
The instrument's wide of field of view combined with the forward motion of the satellite enables it to observe the same site from different viewing angles. As a result, we can see significant variations in brightness depending on the viewing direction.
This unique capability will allow POLDER 2 to characterize the directional properties of solar radiation reflected by the Earth's surface and atmosphere, leading to more accurate corrections for directional and atmospheric effects, and better determination of target area properties.
- CNES/NASDA PRESS RELEASE
Earth Observation Research and application Center, Japan Aerospace Exploration Agency
ALL RIGHTS RESERVED.