The Satellite Infrared Spectrometer (SIRS) on the Nimbus III satellite was designed to measure the earth’s spectral radiances in the 15-µm band of carbon dioxide. From simultaneous measurements of spectral radiances it is possible to obtain the vertical temperature profile of the atmosphere. The measurements are approximated by the integral equation of radiative transfer, modified by one or two layers of clouds. A solution requires that the surface radiative temperature and the surface air temperature be known. By iteration, a solution based upon the statistical behavior of the atmosphere is obtained for the free air temperature and the cloud heights and amounts. Examples are presented, comparing the SIRS soundings with coincident radiosonde soundings. The results from this experiment indicate that the technique can be applied as a routine observing tool for meteorological use.
D. Q. Wark, "SIRS: An Experiment to Measure the Free Air Temperature from a Satellite," Appl. Opt. 9, 1761-1766 (1970)