One of the first photos taken by Envisat, ESA's Earth observation satellite in April 2002.
This image is a colour composite generated from ASAR data acquired on 8 April 2002 in Alternating Polarisation (AP) Mode. The red channel contains the VV polarised image; the green channel contains the HH polarised image; the blue channel contains the magnitude of the difference between the amplitudes in VV and HH.
It shows an area, 100 km wide, around the city of Dzerzhinsk in Russia (towards bottom right), 300 km east of Moscow. In the north can be seen the lower part of the Gorkovskoye Reservoir, formed by a dam across the Volga, Europe’s longest river. In the south can be seen the Oka river, a tributary of the Volga. Urban areas are generally visible in bright yellow tones, indicating equally high backscatter in VV and HH polarisation. The green/yellow colour that dominates the image results from the extensive forests in this region (medium backscatter in VV and HH). Agricultural land in the river plains to the east and south appears in magenta and purple shades (VV backscatter dominates). A number of small river systems, which are probably still frozen, are highlighted in cyan (dominant HH backscatter).