An optimized line by line code for plume signature calculations II. Comparisons with measurements

Measurements of transmission spectra in the infrared have been made in order to test the quality of the theoretical and numerical approach developed in paper I. Two different laboratory experiments have been built which try to simulate optical paths representative of those involved by plume signature. The first, based on a 50 m long White cell and a grating spectrometer, provides experimental results for optical paths of up to about 1 km. These data, representative of the atmospheric paths involved by the considered signature applications, enable a check of the model used for far line wings. In the second set-up, a Fourier transform spectrometer is used with two adjacent cells, which are at high and low temperature, respectively. This configuration schematizes the hot + cold gases that are involved in plume signature. Comparisons between measured and computed values demonstrate the quality of the model and data used. Only small discrepancies remain which are due to imperfections of spectroscopic databases and the neglect of line-mixing effects.