The following sequence presents the individual steps of the DOAS procedure. The steps in this presentation divide into the following six stages:

1. Normalisation of the solar irradiance and earthshine spectra to produce an absorption spectrum (steps 4..6).
2. Subtraction of a low-order polynomial to remove the effects of broadband components — principally Rayleigh and Mie scattering — and produce a differential absorption spectrum (steps 7..9).
3. Compensation for the Ring effect through the fitting of a Ring pseudo-absorber curve (steps 10..12).
4. Fitting of an NO₂ reference curve (steps 13..15).
5. Fitting of an O₃ reference curve (steps 16..18).
6. Fitting of an H₂O reference curve (steps 19..21).

Note that these steps are presented separately here only for reasons of clarity. In practice, these steps are usually performed simultaneously.