STEAM measurement concept

1
STEAM measurement concept

• Telescope with intermediate optics place an image
  of the limb at the focal plane.
• The optics design has to allow 30 km (for the 340
  GHz range) or about 30 arcmin field of view.
• Similar to modern bolometer or receiver arrays,
  the incoming radiation is coupled to an array of
  horns.
• The horns can be either lens horn combinations or
  with mirrors.
• If polarisation is use to separate the beams they
  may be put as close as 3 km apart.
• The intermediate spacing is filled by either
  spacecraft nodding or scan mirror.
• With less beams the sensitivity is reduced and
  scan speed has to increase.

2
STEAM

• 340 GHz receivers covering 5 to 28 km, as option
  with nadir view.
• Mode 1 324.0 - 332.5 and 343.8 - 351.8 GHz in
  DSB mode, H2O, O3 and CO.
• Mode 2 331.6 - 339.6 and 351.4 - 359.4 GHz in
  DSB mode, HDO, and HCN.
• Optional stratospheric band 489.5 - 493.5 and
  499.0 - 503.0 GHz in DSB mode, 15 to 38 km range.
• Optical instrument
• 1 to 1.5 metre CFRP antenna.
• 4 year lifetime in 0900 ascending node, sunsync
  polar orbit at 700 km altitude
• Optional on-board real time processing
• 1 armin pitch real time control