Profilers/Sounders
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"
SSU