Abstract: The Hyperspectral Infrared Atmospheric Sounder (HIRAS) instrument onboard the Feng Yun-3D (FY-3D) satellite, launched on November 15, 2017, can be employed to retrieve column concentration of CO₂ with strong absorption band sat 15 μm and 4.3 μm. The HIRAS contributes to monitoring constellations for global CO₂ observation by comparison with data of other greenhouse gas sensors. Thus, the selection of a band which is concurrently sensitive to CO₂ changes and resistant to interference from other parameters is one of the most critical tasks to enable use of the satellite for practical applications. First, based on the line-by-line radiative transfer model, the HIRAS radiance in the hyperspectral 15 μm band was simulated for five standard atmospheric models,and the responses of given channels to the perturbation of CO₂ and other atmospheric components (H₂O, O₃, surface temperature, and emissivity) were analyzed. Second,using the signal-to-interference ratio,the CO₂ response, and the Jacobian profiles as criteria, five different sets of channels for each condition were selected by the Optimal Sensitivity Profile (OSP) method; this was accompanied by a discussion of channel differences for different atmosphere stratification. Third, experiments involving different levels of instrumental noise showed that the lower the instrument's noise, the more helpful it is to select a CO₂ sensitive height in the stratosphere. The results of the channel selection in this paper present references for instrument design in the future.

Key words: CO₂ sensitivity, Hyperspectral Infrared Sounder, channel selection, Feng Yun 3