This section discusses two categories of interactions that affect the earthshine spectrum measured at the satellite.

• Absorption and scattering
  On its route to the satellite-based spectrometer solar radiation might undergo one or many interactions with the atmosphere and or the surface. The interaction that interests us is absorption by NO₂, but the earthshine measured at the satellite is imprinted with the results of many interactions that can involve different types of scattering and/or reflection. Solar radiation can also be absorbed in many ways, both in the atmosphere and on the surface, and not only by tropospheric NO₂.
• The Ring effect
  Rotational Raman scattering can also have a significant impact on the measured radiances, the signature of which in the DOAS retrieval is often called the Ring effect.