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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 12, issue 5
Ann. Geophys., 12, 417–421, 1994
https://doi.org/10.1007/s00585-994-0417-5
© European Geosciences Union 1994
Ann. Geophys., 12, 417–421, 1994
https://doi.org/10.1007/s00585-994-0417-5
© European Geosciences Union 1994

  30 Apr 1994

30 Apr 1994

Evaluation of infrared emission spectra of aircraft exhaust with the FitFas software

E. Lindermeir E. Lindermeir

Abstract. A Fourier transform spectrometer was used to measure infrared spectra of the exhaust gas of an aircraft's jet engine. The measured spectra were modelled by use of the program FASCODE. For this simulation, the inhomogeneous gas mixture is divided into several homogenous layers which are characterized by their geometrical extents, temperatures, pressures and chemical compositions. To obtain values for the temperatures and the CO, NO, H2O and CO2 concentrations of the layers a nonlinear least-squares algorithm was implemented. The program (FITFAS) not only changes the parameters to find the minimum of the squared differences between measurement and calculation; it also provides the variances and covariances of the parameters. Thus information is obtained to which parameters (besides the interesting ones) must be fitted (or be accurately known). It also tells us whether or not another spectral interval is more suitable for the determination of a specific parameter.

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