Fig 3.3.1.14.1: NO2 reference curve fitted to the Ring compensated absorption curve.
Image: AT2-ELS
The fitting process is a least squares fitting algorithm that minimises the sum of the squares of the ordinate differences (sometimes termed 'residuals') over the selected wavelength range.
A similar procedure will be followed in subsequent steps for the reference spectra of the other relevant trace gas species.
The scaling factor derived for the NO2 cross-section is the NO2 slant column SCNO2, the quantity of interest.