GOES Sounders.  

• The Visible and Infrared Spin Scan Radiometer (VISSR) Atmospheric Sounder (VAS) was introduced on GOES-4 in 1981.
• The VAS hardware is shown to the right -->
• The GOES-8 sounder has 18 thermal infrared bands plus a low-resolution visible band.
• The field of view (FOV) is 8 km and is sampled every 10 km.
• The GOES-8 sounder spectral selection:
  • six bands in the 15 um (longwave) band,
  • a split-window pair,
  • three midtropospheric water-sensitive bands
  • an ozone band
  • five 4 um (shortwave) bands
  • a visible band.
• The GOES-8 sounder's design goal, like the imager's, is to provide brightness temperatures with 1.0 K absolute accuracy and 0.3 K relative precision.
• NOTE: No Sounding retrieval is possible in cloudy areas!