Atmospheric interference


Atmospheric window
 
Atmospheric window
 
The radiation from the Sun and the reflection from the surface of the Earth pass through the atmosphere before they reach the satellite sensor. The atmospheric content of greenhouse gases absorbs part of the radiation from the Earth. Ozone acts as an almost complete barrier to ultraviolet radiation and almost all radiation in the range of 9.5 - 10 micrometres is absorbed. Aqueous vapours and carbon dioxide are very effective greenhouse gases which absorb radiation in many different wavelengths.

The wavelengths where the majority of the radiation pass through are called 'atmospheric windows'. Fortunately a great deal of the visible light also passes through, or else daylight would never reach the surface! The atmosphere is also almost 100% translucent in certain ranges of the near infrared spectrum, which makes satellite observation possible with a minimum of atmospheric distortion. The thermal infrared range from 10 - 12 micrometres is used in measuring surface temperatures of the ground, water and clouds.

Even though remote sensing takes place in the atmospheric windows, it is still to some extent interfered with by diffusion and absorption in the atmosphere.

For this reason, remote sensing may often be slightly distorted and need to be adjusted with subsequent digital image processing.
 
 
  
Last update: 26 November 2009


Remote sensing in depth

 •  Introduction (http://www.esa.int/SPECIALS/Eduspace_EN/SEM7IQ3Z2OF_0.html)
 •  Radar technology (http://www.esa.int/SPECIALS/Eduspace_EN/SEMHUESTGOF_0.html)
 •  Landsat MSS channels (http://www.esa.int/SPECIALS/Eduspace_EN/SEMRTCSTGOF_0.html)
 •  Spectral signatures (http://www.esa.int/SPECIALS/Eduspace_EN/SEMPNQ3Z2OF_0.html)
 •  Vegetation mapping (http://www.esa.int/SPECIALS/Eduspace_EN/SEM6SQ3Z2OF_0.html)
 •  Area classification (http://www.esa.int/SPECIALS/Eduspace_EN/SEMP5R3Z2OF_0.html)