We present a novel method for the quantitative analysis of spectra based on the properties of the cross correlation between a real spectrum and either a numerical synthesis or a laboratory simulation. We propose a new goodness-of-fit criterion called the heteromorphic coefficient H that has the property of being zero when a fit is achieved and varying smoothly through zero as the iteration proceeds, providing a powerful tool for automatic or near-automatic analysis. We also show that H can be rendered substantially noise-immune, permitting the analysis of very weak spectra well below the apparent noise level and, as a by-product, providing Doppler shift and radial velocity information with excellent precision. The technique is in regular use in the Atmospheric Trace Molecule Spectroscopy (ATMOS) project and operates in an interactive, real-time computing environment with turn-around times of a few seconds or less.
© 1988 Optical Society of AmericaFull Article | PDF Article