SELECTION OF SOUNDING CHANNELS FOR THE HIGH-RESOLUTION DYNAMICS LIMB SOUNDER

We describe the scientific design work behind the selection of the IR spectral passbands for the 21 sounding channels of the High Resolution Dynamics Limb Sounder (HIRDLS), which is scheduled to fly aboard the Earth Observing System chemistry platform at the beginning of the next century. At least one radiometer channel must be used for each gas th at is being measured. Preferably the interfering contributions to the radiance by other gases in a channel should he small, but the principa l requirements are that the desired emission be measured with high sig nal-to-noise ratio and that there be separate channels for the measure ment of interfering species. However, more than one channel is require d for providing full altitude coverage of those target gases such as C O2, H2O, and O-3, which have emission bands whose centers become optic ally thick in the middle atmosphere. Further channels, in which gaseou s absorption is low, are required for the characterization of aerosol effects. We describe the HIRDLS channels selected for each gas, with e mphasis on signal-to-noise considerations and altitude coverage, the e limination of contaminating signal between channels, and nonlocal ther modynamic equilibrium processes for high-altitude sounding and space v iew definition. (C) 1995 Optical Society of America