@prefix ns0: <http://gcmd.gsfc.nasa.gov/kms#> .
@prefix skos: <http://www.w3.org/2004/02/skos/core#> .

<https://gcmd.earthdata.nasa.gov/kms/concept/46421a95-3e0a-4cac-af85-8140c2b99774>
  ns0:altLabel [ ] ;
  skos:definition """The SSU, supplied by the United Kingdom Meteorological
      Office, employs a selective absorption technique to make
      measurements in three channels.  The principles of its operation
      are based on the Selective Chopper Radiometer (SCR) flown on
      Nimbus-4 and, and the Pressure Modulation Radiometer (PMR) flown
      on Nimbus-6.

      The SSU makes use of the pressure modulation technique to
      measure radiation emitted from carbon dioxide at the top of the
      earth's atmosphere.  A cell of carbon dioxide gas in the
      instrument's optical path has its pressure changed (at about a 40
      Hz rate) in a cyclic manner.  The spectral characteristics of the
      channel and, therefore, the height of the weighting function is
      then determined by the pressure in the cell during the period of
      integration.  By using three cells filled at different pressures,
      weighting functions peaking at three different heights can be
      obtained.

      The primary objective of the instrument is top obtain data
      from which stratospheric (25-50 km) temperature profiles can be
      determined.  This instrument was used in conjunction with the
      HIRS/2 and MSU to determine temperature profiles from the surface
      to 50 km (see the sensor reference for TIROS OPER VERTICAL
      SOUNDER).

      SSU Characteristics:
                                  PRESSURE OF
                                   WEIGHTING
                                 FUNCTION PEAK
                     CELL        --------------
      CHANNEL     PRESSURE(mb)   (mb)       (km)
      -------     ----------     ----       ----
      1             100          15         29
      2              35           5         37
       3              10           1.5       45
      _________________________________________________________________
      Entry taken from:
      Rao,P.K., S.J. Holmes, R.K. Anderson, J.S. Winston, P.E. Lehr,
           Weather Satellites: Systems, Data, and Environmental
           Applications, American Meteorological Society, Boston, 1990.
           ISBN 0-933876-66-1
      Colwell,R.N. (Editor-in-Chief), Manual of Remote Sensing: Second
           Edition, Volume I, American Society of Photogrammetry, 1983.
      Cornillon, A Guide to Environmental Satellite Data, University of
           Rhode Island Marine Technical Report 79, 1982.

      Additional information available at
      "http://www.eumetsat.de/en/index.html?area=left4.html&body=/en/
area4/aapp/ssu.html&a=420&b=1&c=400&d=400&e=0\""""@en ;
  skos:prefLabel "SSU"@en ;
  skos:inScheme <https://gcmd.earthdata.nasa.gov/kms/concepts/concept_scheme/instruments> ;
  skos:broader <https://gcmd.earthdata.nasa.gov/kms/concept/4190ebdc-e89a-4f3f-bc74-b2af4c68d009> ;
  a skos:Concept .

<https://gcmd.earthdata.nasa.gov/kms/concept/4190ebdc-e89a-4f3f-bc74-b2af4c68d009>
  skos:prefLabel "Profilers/Sounders"@en ;
  a skos:Concept ;
  skos:narrower <https://gcmd.earthdata.nasa.gov/kms/concept/46421a95-3e0a-4cac-af85-8140c2b99774> .