IASI has been designed for operational meteorological soundings with a very high level of accuracy (specifications on Temperature accuracy: 1K for 1 km and 10 % for humidity) being devoted to improved medium range weather forecast. It is also designed for atmospheric chemistry aiming at estimating and monitoring trace gases like ozone, methane or carbon monoxide on a global scale. The IASI system includes the 3 instruments, a data processing software integrated in the EPS ground segment and a technical expertise centre implemented in CNES Toulouse.
The measurement technique is based on passive IR remote sensing using an accurately calibrated Fourier Transform Spectrometer operating in the 3.7 - 15.5 µm spectral range and an associated infrared imager operating in the 10.3 - 12.5 µm spectral range. The optical configuration of the sounder is based on a Michelson interferometer. The integrated infrared imager allows the co registration of the IASI sounder with AVHRR imager on-board METOP.

CNES is leading the IASI program in association with EUMETSAT.
CNES has technical oversight responsibility for the instruments development up to their deliveries to EUMETSAT.
CNES is also responsible for developping the Data Processing Software which is implemented in the EUMETSAT Polar System ground segment and for developping and operating a Technical Expertise Center.
EUMETSAT is responsible for operating the instrument and the associated data processing, archiving and distribution of the IASI data to users.