Measuring ozone and carbon monoxide concentrations in the boundary layer of the atmosphere (the atmospheric layer near the surface, between 0 and 3 km roughly) is a major challenge for air quality. Infrared sounding, providing profiles with information at several vertical levels, is a must for pollution monitoring.

In this framework, CNES is currently leading a phase-A study for the instrument SIFTI, Static Infrared Fourier Transform Interferometer, devoted to ozone and CO measurements. In the TRAQ proposal to the ESA Earth Explorer mission, SIFTI could be associated with two other instruments: TROPOMI, a UV-VIS spectro-imager and OCAPI, a multi-angle polarised spectro-radiometer based on the Polder or Parasol heritage.