IASI is a spectrometer, that is an instrument which measures the spectral distribution of the radiation. The instrument concept is based on the Michelson interferometer. This concept was validated by CNES on a laboratory breadboard.

The main characteristics are defined in order to meet the mission requirements and to be compliant with the satellite capabilities. In particular, the spectral resolution et the radiometric resolution deals with the retrivial of temperature and humidity profile with a vertical resolution of one kilometer and accuracies of one kelvin and 10% respectively.

The field of view is compatible with the companion instruments of the meteorological core payload of Metop.

Due to hight performance requirements, innovative technical solutions and technologies are used to build the instrument components.

The IASI instrument comprises an on-board management unit and a digital processing subsystem which performs the inverse Fourier transform and the radiometric calibration. It includes also an infrared imager.